U.S. patent application number 13/033923 was filed with the patent office on 2011-08-25 for system and method for inductively transferring ac power and self alignment between a vehicle and a recharging station.
This patent application is currently assigned to EVATRAN LLC. Invention is credited to Robert Atkins, Vincenzo I. Paparo.
Application Number | 20110204845 13/033923 |
Document ID | / |
Family ID | 44475969 |
Filed Date | 2011-08-25 |
United States Patent
Application |
20110204845 |
Kind Code |
A1 |
Paparo; Vincenzo I. ; et
al. |
August 25, 2011 |
SYSTEM AND METHOD FOR INDUCTIVELY TRANSFERRING AC POWER AND SELF
ALIGNMENT BETWEEN A VEHICLE AND A RECHARGING STATION
Abstract
A method and apparatus for hands free inductive charging of
batteries for an electric vehicle is characterized by the use of a
transformer having a primary coil connected with a charging station
and a secondary coil connected with a vehicle. More particularly,
the when the vehicle is parked adjacent to the charging station,
the primary coil is displaced via a self alignment mechanism to
position the primary coil adjacent to the secondary coil to
maximize the inductive transfer of charging current to the
secondary coil. The self alignment mechanism preferably utilizes
feedback signals from the secondary coil to automatically displace
the primary coil in three directions to position the primary coil
for maximum efficiency of the transformer.
Inventors: |
Paparo; Vincenzo I.;
(Daleville, VA) ; Atkins; Robert; (Wytheville,
VA) |
Assignee: |
EVATRAN LLC
Wytheville
VA
|
Family ID: |
44475969 |
Appl. No.: |
13/033923 |
Filed: |
February 24, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61308099 |
Feb 25, 2010 |
|
|
|
Current U.S.
Class: |
320/108 ;
29/602.1; 336/178 |
Current CPC
Class: |
H01F 38/14 20130101;
B60L 53/38 20190201; Y02T 90/121 20130101; H02J 7/0044 20130101;
Y02T 90/14 20130101; Y02T 10/7005 20130101; H02J 50/10 20160201;
Y02T 90/125 20130101; Y02T 10/7072 20130101; H02J 50/90 20160201;
B60L 53/126 20190201; H02J 7/025 20130101; B60L 53/122 20190201;
Y10T 29/4902 20150115; Y02T 10/70 20130101; Y02T 90/122 20130101;
Y02T 90/12 20130101 |
Class at
Publication: |
320/108 ;
336/178; 29/602.1 |
International
Class: |
H02J 7/00 20060101
H02J007/00; H01F 17/04 20060101 H01F017/04; H01F 41/00 20060101
H01F041/00 |
Claims
1. A power transformer, comprising: a first core including first,
second, and third pole areas; and a second core including first,
second, and third pole areas, and wherein the first core and the
second core are separated by first, second, and third air gaps, the
first air gap separating the first pole of the first core and the
first pole of the second core, the second air gap separating the
second pole of the first core and the second pole of the second
core, and the third air gap separating the third pole of the first
core and the third pole of the second core.
2. The power transformer according to claim 1, wherein the first
core further comprises a first winding area wrapped about a first
conductive material connected with a primary voltage source; the
second core further comprises a second winding area wrapped about a
second conductive material configured to provide current; the
first, second, and third poles of the first core, and the first,
second, and third poles of the second core are substantially
similar in size and shape; the first and second windings are
substantially similar in cross sectional area; and a ratio of
surface area of the first pole to the cross sectional area of the
first winding area is between about a 2.0 and about 5.0.
3. The power transformer according to claim 2, wherein the ratio of
surface area of the first pole to the cross sectional area of the
first winding area is about 3.2.
4. The power transformer according to claim 1, wherein power input
to the primary core is inductively coupled through the first,
second, and third air gaps to the second core.
5. The power transformer according to claim 1, wherein the first
core and the second core are shaped like a flared "C".
6. A system for charging a rechargeable battery, comprising: a
power transformer including a first core, the first core including
first, second, and third pole areas; and a second core, the second
core including first, second, and third pole areas, and wherein the
first core and the second core are separated by first, second, and
third air gaps, the first air gap separating the first pole of the
first core and the first pole of the second core, the second air
gap separating the second pole of the first core and the second
pole of the second core, and the third air gap separating the third
pole of the first core and the third pole of the second core; and a
semi-permeable magnetic membrane comprising an epoxy binder and a
ferromagnetic material embedded within the epoxy binder, wherein
the semi-permeable magnetic membrane coats each of the first,
second, and third poles on the first core, and the semi-permeable
magnetic membrane coats each of the first, second, and third poles
on the second core, the first core is electrically connected to a
primary voltage source, and the second core is located apart from
the first core until recharging occurs and further is electrically
connected to the rechargeable battery.
7. The system for recharging according to claim 6, wherein the
ferromagnetic material includes at least one of iron and steel.
8. The system for recharging according to claim 6, wherein the
semi-permeable magnetic material comprises a mixture of between 30%
and 90% iron or steel filings in an epoxy binder.
9. An inductively coupled battery recharging system, comprising: a
first inductive winding coupled to an exterior power source and
including a first core, a first winding area of the first core
including a first winding cross sectional area A.sub.WC1; a first
pole section of the first core including a first pole sectional
area A.sub.C1P1, a second pole section of the first core including
a second pole sectional area A.sub.C1P2, and a third pole section
of the first core including a third pole section area A.sub.C1P3,
wherein A.sub.C1P1, A.sub.C1P2, and A.sub.C1P3 are substantially
similar in shape and size; and a second inductive winding coupled
to a rechargeable battery and including a second core, a second
winding area of the second core including a second winding cross
sectional area A.sub.WC2; a first pole section of the second core
including a first pole sectional area A.sub.C2P1, and a second pole
section of the second core includes a second pole sectional area
A.sub.C2P2, and a third pole section of the second core including a
third pole sectional area A.sub.C2P3, wherein A.sub.C2P1 and
A.sub.C2P2 and A.sub.C2P3 are substantially similar in shape and
size, A.sub.WC1 and A.sub.WC2 are substantially similar in shape
and size, and A.sub.C1P1 and A.sub.C1P2 and A.sub.C1P3 and
A.sub.C2P1 and A.sub.C2P2 and A.sub.C2P3 are substantially similar
in shape and size, and further wherein, when the ratio of the area
of the pole of the core to the area of the winding of the core is
between 2.0- and 5.0, both a first magnetic flux area formed
between the first pole of the first core and the first pole of the
second core, and a second magnetic flux area formed between the
second pole of the first core and the second pole of the second
core, and a third magnetic flux area formed between the third pole
of the first core and the third pole of the second core are
substantially contained, respectively, within a first volume formed
by the cross sectional areas of the first pole of the first core
and the first pole of the second core, and the second pole of the
first core and the second pole of the second core, and the third
pole of the first core and the third pole of the second core.
10. An inductively coupled battery recharging system as defined in
claim 1, wherein the ratio of the area of the pole of the core to
the area of the winding of the core is about 3.2.
11. An inductively coupled battery recharging system as defined in
claim 9, and further comprising a semi-permeable magnetic material
comprising an epoxy binder and a ferromagnetic material embedded
within the epoxy binder for coating said first and second poles on
said first and second cores, respectively.
12. An inductively coupled battery recharging system as defined in
claim 11, wherein the ferromagnetic material includes at least one
of iron and steel.
13. An inductively coupled battery recharging system as defined in
claim 11, wherein the semi-permeable magnetic material comprises a
mixture of between 30% and 90% of at least one of iron and steel
filings in an epoxy binder.
14. A method for increasing the efficiency of energy transfer in a
transformer having at least two cores, each core having at least
two poles, comprising the steps of embedding a ferromagnetic
material into an epoxy binder to provide a semi-permeable magnetic
material; and applying the semi-permeable magnetic material to the
at least two poles of each core.
15. The method of claim, wherein said embedding step comprises
forming a mixture of between 30% and 90% of at least one of iron
and steel filings in the epoxy binder.
16. Apparatus for inductively charging a battery in a vehicle,
comprising (a) a fixture; and (b) a transformer including (1) a
primary coil mounted on said fixture; and (2) a secondary coil
mounted on the vehicle, whereby when the vehicle is positioned
adjacent to said fixture and said secondary coil is opposite said
primary coil and power is supplied to said primary coil, inductive
power is transmitted to said secondary coil to charge the vehicle
battery.
17. Apparatus as defined in claim 16, wherein said fixture includes
a movable interface plate, said primary coil being mounted on said
interface plate.
18. Apparatus as defined in claim 17, and further comprising means
for displacing said interface plate to position said primary coil
proximate to said secondary coil.
19. Apparatus as defined in claim 18, wherein said displacing means
comprises a guide plate mounted on said interface plate, said guide
plate engaging a member on said vehicle and being displaced
relative to said vehicle member to displace said interface plate
laterally and longitudinally relative to the vehicle to align said
primary and secondary coils.
20. Apparatus as defined in claim 19, wherein said interface plate
is pivotally connected with said fixture.
21. Apparatus as defined in claim 20, wherein said displacing means
further comprises a spring for pivoting said interface plate
vertically to position said primary coil proximate to said
secondary coil.
22. Apparatus as defined in claim 18, and further comprising a
first control module connected with said fixture and a second
control module connected with said second coil said first control
module controlling the operation of said first coil and said second
control module controlling the operation of said second coil.
23. Apparatus as defined in claim 22, and wherein said first and
second control modules include wireless communication devices for
sending information between said first and second control
modules.
24. Apparatus as defined in claim 23, wherein said first control
module is connected with said displacing means to control the
movement of said interface plate.
25. Apparatus as defined in claim 24, wherein said displacing means
moves said interface plate laterally, longitudinally and vertically
to position said first coil proximate to said second coil.
26. Apparatus as defined in claim 25, wherein said communication
devices transmit information between said first and second modules
relating to the strength of the magnetic field generated by said
coils in order to position said interface plate in a position where
energy transferred from said first coil to said second coil is
maximized.
27. A method for inductively charging a battery in a vehicle,
comprising the steps of (a) connecting the secondary coil of a
transformer with the vehicle battery and the primary coil of a
transformer with a fixture; (b) positioning the vehicle adjacent to
the fixture; (c) aligning the primary coil with the secondary coil
to maximize the inductive transfer of power from said primary coil
to said secondary coil, thereby to deliver power to the
battery.
28. A method as defined in claim 25, wherein said aligning step
includes the steps of (a) supplying a low level of AC current to
said primary coil to induce AC current in the secondary coil; (b)
measuring the AC current induced in the secondary coil to determine
the efficiency of the inductive transfer of power between said
coils; (c) positioning said primary coil to maximize the efficiency
of the inductive transfer of power.
29. A method as defined in claim 28, and further comprising the
step of transmitting a signal corresponding to the level of induced
current in the secondary coil to the fixture to control the
positioning of said primary coil.
30. A method as defined in claim 29, and further comprising the
step of rectifying the AC current supplied to the primary coil of
the transformer.
Description
[0001] This application claims the benefit of U.S. provisional
patent application No. 61/308,099 filed Feb. 25, 2010.
BACKGROUND OF THE INVENTION
[0002] It is now well established that our nation, and many other
nations, face serious environmental and fuel supply problems with
internal combustion engines. Most internal combustion engines run
on either gasoline or diesel fuels, both of which are petroleum
products. As is well known, the world's oil supply is generally
found far beneath the planet's surface, and in only a few specific
locations. Enormous amounts of infrastructure and significant costs
are involved in finding, extracting, and processing the oil into
gasoline and diesel fuels, and further significant costs are
incurred in the storage, transportation, and sale of the finished
gasoline and diesel fuel products.
[0003] It is well established that there is only a finite supply of
petroleum in our world, and further that the byproducts of
combustion, among them carbon monoxide (CO), can and have caused
environmental damage to our planet, and have created health risks
to humans as well. Thus our nation, as well as many others, faces
the problems of a strong reliance on petroleum products for
transportation, heating and manufacturing, and that those petroleum
products are in short supply and damaging our world and
ourselves.
[0004] As a result, there is increased attention on lessening both
the reliance on petroleum products and on the negative effects of
burning petroleum products. A partial solution is the use of
electric vehicles. Electric vehicles, whether purely electric or in
the form of gasoline-electric hybrid vehicles, will reduce
pollution and the use of petroleum products, especially in the form
of gasoline since most electricity-producing power plants run on
either natural gas, oil, nuclear power, or coal. While each of
these alternative fuel sources produces its own set of issues in
regard to the environmental and supply debate, it is generally
believed that if a nation, in particular the United States of
America, could replace significant amounts of its internal
combustion automobile engines with electric vehicles, local,
national and perhaps global pollution levels would decrease.
[0005] There have been, therefore, significant expenditures of
time, effort, and financial resources to launch the use of at least
gasoline-electric hybrid (herein after "hybrid") vehicles, as well
as vehicles that run exclusively on electricity (herein after, both
types of automobiles shall be referred to simply as "electric
vehicles"), by private automobile manufacturers, and government
leaders. Of the many obstacles that have presented themselves to
those in the industry of manufacturing electric vehicles, one
significant problem is that of recharging the batteries, cells, or
other electrical energy storage devices.
[0006] Vehicle energy storage systems are normally recharged using
direct contact conductors between an alternating current (AC)
source such as is found in most homes in the form or electrical
outlets; nominally 120 or 240 VAC. A well known example of a direct
contact conductor is a two or three pronged plug normally found
with any electrical device. Manually plugging a two or three
pronged plug from a charging device to the electric automobile
requires that conductors carrying potentially lethal voltages be
handled. In addition, the conductors may be exposed, tampered with,
or damaged, or otherwise present hazards to the operator or other
naive subjects in the vicinity of the charging vehicle. Although
most household current is about 120 VAC single phase, in order to
recharge electric vehicle batteries in a reasonable amount of time
(two-four hours), it is anticipated that a connection to a 240 VAC
source would be required because of the size and capacity of such
batteries. Household current from a 240 VAC source is used in most
electric clothes dryers and clothes washing machines. The
owner/user of the electric vehicle would then be required to
manually interact with the higher voltage three pronged plug and
connect it at the beginning of the charging cycle, and disconnect
it at the end of the charging cycle. The connection and
disconnection of three pronged plugs carrying 240 VAC presents an
inconvenient and potentially hazardous method of vehicle interface,
particularly in inclement weather.
[0007] In order to alleviate the problem of using two or three
pronged conductors, exemplary embodiments of the present invention
utilize an inductive charging system to transfer power to the
electric vehicle. Inductive charging, as is known to those of skill
in the art, utilizes a transformer to charge the battery of the
target device. One example of known inductive charging systems is
that used to charge electric toothbrushes.
[0008] Some electric toothbrushes use non-rechargeable batteries,
some use rechargeable batteries that are physically connected to
two or more external connectors that interface with matching
connectors on a base station. But in an inductive recharging system
for an electric toothbrush, there are no such external connects.
Instead, a first transformer in the base receives the primary
voltage from either a wall source, or a stepped down voltage from
some internal circuitry, and creates a time-varying magnetic field
through the effect of a ferro-magnetic iron core used in the base
transformer. The time-varying magnetic field permeates into the
secondary transformer core in the electric toothbrush, and a
time-varying voltage is produced on the windings that surround the
secondary transformer core. This voltage is fed to internal
circuitry where it is rectified and filtered and then input to the
battery to recharge it. The same general principles apply to
electric vehicle inductive charging systems.
[0009] One item briefly discussed above is the time varying aspect
of the AC voltage, and hence the time-varying aspect of the
magnetic fields in both the primary and secondary transformer
cores. Typically, house current in the U.S. operates at about 60
hertz (Hz), or cycles per second. The problem with using a voltage
that oscillates at 60 Hz, is that the size of the components in an
inductive charging system is inversely proportional to the
frequency, and thus the lower the frequency of the voltage, the
greater the size of the inductive charging system. As those of
ordinary skill in the automotive industry can attest, size is
extremely critical to vehicle manufacturers because it is very
important to automotive owners. The size and weight of an object
directly affects the fuel mileage of the vehicle. Thus in other
inductive charging systems, high frequency voltages, normally above
10 kHz, have been used to transfer power by radiation and tuned
coils. There is, however, a cost associated with the use of higher
frequency voltages and that is the subsequent loss of efficiency.
The higher the frequency at which the charging system operates, the
less efficient is the charging system. A less efficient charging
system means that much more power must be input into the primary
side of the recharging system resulting in greater cost.
FIELD OF THE INVENTION
[0010] The present invention relates to inductive proximity
charging. More particularly, the invention relates to a system and
method for increasing the efficiency and reducing the noise of a
gapped transformer used in inductive charging of a vehicle and to a
self-aligning proximity recharging station for a parked
vehicle.
BRIEF DESCRIPTION OF THE PRIOR ART
[0011] Gapped transformers are transformers that are formed with
two component pieces known as cores. Gapped transformers generally
are less efficient for similarly sized and configured transformers
than non-gapped transformers which are manufactured as one
continuous iron core. As used herein, efficiency is measured as the
ratio of power output by the secondary windings of the gapped
transformer to the power input by the primary windings of the
gapped transformer, which is usually connected to some primary
source of power, normally 120 or 240 volts alternating current
(VAC).
[0012] Thus, a general need exists for gapped transformers for
inductive charging that can increase efficiency and minimize
induced noise.
SUMMARY OF THE INVENTION
[0013] It is therefore a general aspect of the invention to provide
a system and method for reducing induced noise, increasing the
efficiency of a gapped transformer used in inductive charging, and
a self-aligning proximity recharging station that will obviate or
minimize problems of the type previously described.
[0014] According to a primary object of the invention, the
apparatus for charging a battery in a vehicle includes a fixture
having an interface plate which is movable in a number of
directions. The gapped transformer includes a primary coil mounted
on the interface plate and secondary coil mounted on the vehicle. A
displacement mechanism is connected with the interface plate to
position the primary coil proximate to the secondary coil to
maximize the inductive transfer of power from the primary coil to
the secondary coil which is used to charge the battery.
[0015] In one embodiment, the displacement mechanism includes a
guide plate mounted on the interface plate. When a vehicle is
parked adjacent to the fixture, a member on the vehicle engages the
guide plate to displace the interface plate laterally and
longitudinally relative to the vehicle to align the primary coil
with the secondary coil. In addition, a spring connected with the
interface plate displaces the interface plate vertically to
position it closer to the secondary coil.
[0016] In a preferred embodiment, the interface plate is positioned
relative to the vehicle by wireless communication system. The
transformer includes control modules connected with the primary and
second coils, with each module including a wireless communication
device. When the vehicle is parked adjacent to the fixture, a low
level of AC current is supplied to the primary coil to induce an AC
current in the secondary coil. The level of the induced current in
the secondary coil is transmitted to the control module connected
with the primary coil. The control module activates the
displacement mechanism to move the interface plate laterally,
longitudinally, and vertically to position the primary coil
proximate to the secondary coil in a position to maximize the
inductive transfer of power. Once properly positioned, the level of
AC current delivered to the primary coil is maximized to
inductively transfer the current to the secondary coil where it is
delivered to a charger to charge the vehicle batter.
[0017] The transformer further includes first and second cores for
the primary and secondary windings, respectively, each of the cores
including first, second, and third pole areas which are separated
by first, second and third air gaps, respectively, when the primary
core is positioned adjacent to the secondary core.
[0018] The transformer cores are formed in a flared C configuration
and a semi-permeable magnetic membrane coats the poles on each
core. The membrane is formed of an epoxy binder with a
ferromagnetic material embedded therein.
BRIEF DESCRIPTION OF THE FIGURES
[0019] Other objects and advantages of the present invention will
become apparent from a study of the following specification when
read in conjunction with the accompanying drawing, in which:
[0020] FIG. 1 is a block diagram of a self-aligning inductive
alternating current (AC) power transfer system according to a first
embodiment of the present invention;
[0021] FIG. 2 is a schematic view of a charging station and the
vehicle incorporating the self-aligning inductive AC power transfer
system of FIG. 1;
[0022] FIG. 3 is a more detailed block diagram of the components of
the self-aligning inductive AC power transfer system illustrated in
FIG. 1;
[0023] FIGS. 4 and 5 top and side views, respectively, of the
self-aligning inductive AC power transfer system as shown in FIG. 1
for charging a vehicle;
[0024] FIG. 6 is front view of a floor mounting system for the
charging portion of the system shown in FIGS. 4 and 5;
[0025] FIG. 7 is a block diagram of a self-aligning inductive AC
power transfer system according to a further embodiment of the
present invention;
[0026] FIG. 8 is a side view of a gapped transformer for use in the
power transfer system according to the present invention;
[0027] FIG. 9 is a view taken along line 9-9 of FIG. 8 showing a
first pole cross sectional surface area of the secondary core of
the gapped transformer of FIG. 8;
[0028] FIG. 10 is a cross sectional view taken along line 10-10 of
FIG. 8 showing a first core cross sectional surface area of the
secondary core of the gapped transformer shown in FIG. 8;
[0029] FIG. 11 is a side view of secondary core of a gapped
transformer according to an embodiment of the present
invention;
[0030] FIG. 12 is a bottom view of the secondary core of FIG. 11
illustrating first and second pole cross sectional surface
areas;
[0031] FIG. 13 is a cross sectional view along line 13-13 of FIG.
11 showing a first core cross sectional surface area of the
secondary core;
[0032] FIG. 14 is side view of a gapped transformer showing an air
space between a primary core and secondary core according to an
embodiment of the present invention;
[0033] FIG. 15 is a front perspective view of the secondary core of
FIG. 11.
[0034] FIG. 16 is a side cut-away view of the gapped transformer of
FIG. 14 including a hermetic epoxy sealing case and a
semi-permeable magnetic membrane according to an embodiment of the
present invention;
[0035] FIG. 17 is a side view of primary and secondary cores of a
gapped transformer according to an alternate embodiment of the
present invention;
[0036] FIG. 18 is a perspective view of the cores of FIG. 17;
[0037] FIG. 19 is a top view of a pole of one of the primary or
secondary cores of FIG. 17;
[0038] FIG. 20 is a side view of the pole of FIG. 19;
[0039] FIG. 21 is a front view of a vehicle induction coil
according to an embodiment of the present invention;
[0040] FIGS. 22A and 22B illustrate a first decrease in magnetic
flux field fringing when a semi-permeable magnetic membrane is used
with a first power transfer system according to an embodiment of
the present invention;
[0041] FIGS. 23A and 23B illustrate a second decrease in magnetic
flux field fringing when a semi-permeable magnetic membrane is used
with a second power transfer system according to an embodiment of
the present invention;
[0042] FIG. 24 is a front perspective view of a floor mounting
system that can be used with a self-aligning inductive alternating
current (AC) power transfer system according to the present
invention;
[0043] FIG. 25 is a top view of the floor mounting system of FIG.
24;
[0044] FIG. 26 is a front cut-away perspective view of the floor
mounting system of FIG. 24;
[0045] FIG. 27 is a cut-away side view of the floor mounting system
of FIG. 24;
[0046] FIG. 28 is a partial cut-away side view of the floor
mounting system of FIG. 24;
[0047] FIG. 29 is a partial top view of a vehicle approaching the
floor mounting system of FIG. 24;
[0048] FIGS. 30A and 30B illustrate different angles of approach
between a vehicle and the floor mounting system;
[0049] FIG. 31 is a partial top view of an alternate embodiment of
a floor mounting system that can be used with a self-aligning
inductive alternating current (AC) power transfer system;
[0050] FIG. 32 is a side view of the floor mounting system of FIG.
31;
[0051] FIG. 33 is a flow diagram illustrating operation of a
self-aligning inductive alternating current (AC) power transfer
system; and
[0052] FIG. 34 is a block diagram of a multiple-user floor mounted
station system according to the present invention.
DETAILED DESCRIPTION
[0053] The self-aligning AC power transfer system (PTS) 100
according to the invention will initially be described with
reference to FIG. 1 The system 100 includes a floor mounting
station (FMS) 102 and a vehicle unit 108. Floor mounting station
102 includes a station electronic power transfer control unit
(station control unit) 104, a station computer control and
communications module 132, station unit indicators 140, and a
station induction coil 303 which is part of an inductive, low
noise, high efficiency AC power transfer system 300. Vehicle unit
108, which is mounted to and within a vehicle 124, includes a
vehicle induction coil 301 (also part of the inductive low noise,
high efficiency AC power transfer system 300), a vehicle electronic
power transfer control unit (vehicle control unit) 112, and a
vehicle computer control and communications module 134. Further
shown in FIG. 1 as part of vehicle 124 are a charger 114, a battery
116, and an electrical engine 144. The floor mounting station is
shown in more detail in FIGS. 4-6 and FIG. 7 illustrates the system
architecture for the self-aligning power transfer system 100
according to the invention.
[0054] Self aligning power transfer system 100 operates to transfer
electrical power in an efficient and low-noise manner to vehicle
124 having batteries 116 that require recharging. Generally, such
vehicles will be motor vehicles, but such vehicles can also include
airplanes, including unmanned aerial vehicles, civilian and
military aircraft, including helicopters, gyroplanes, and all types
of fixed and rotary winged aircraft. Furthermore, self aligning
power transfer system 100 can be used to recharge batteries 116
that are used in boats, submarines, and any and all types of water
borne vessels (e.g., hydrofoils, hovercraft, ground-effect
vehicles, among others). Other, non-limiting examples of vehicles
that can use self aligning power transfer system 100 for recharging
batteries 116 include motorcycles, scooters, trucks, and
recreational vehicles.
[0055] FIG. 2 illustrates the self-aligning inductive power
transfer system 100 as shown in FIG. 1 according to an exemplary
embodiment. In FIG. 2, vehicle 124 includes a vehicle unit 108
having a vehicle induction coil 301 which is visible on the
front-bottom of vehicle 124 as it approaches floor mounting station
102. Floor mounting station 102 is electrically connected to a
power grid. The power from the mounting station is rectified and
filtered and its frequency is changed prior to being input to
station induction coil 303 that is visible on the top of floor
mounting station 102. The operator of the vehicle 124 will use
indicator lights 140 to guide the vehicle 124 to substantially
close to the proper position, and floor mounting station 102 can
self-align itself such that the two induction coils are neatly
aligned as will be developed in greater detail below.
[0056] The self aligning power transfer system 100 transfers power
to vehicle 124 using inductive coupling. In inductive coupling, an
alternating current magnetic field is generated in the primary
induction coil, and is transferred to, or coupled to, a secondary
induction coil that is a component of the vehicle. There, the
alternating current voltage is output from the secondary induction
coil to a charger, which converts the AC voltage to a direct
current (DC) voltage that is used to charge the rechargeable
battery. In order to more efficiently transfer the power
inductively, the self aligning power transfer system 100 uses
specially shaped transformer cores that efficiently transfer the
magnetic field from the primary induction coil through an air gap
to the secondary induction coil with a minimum of loss.
Furthermore, the specially shaped transformer cores minimize
induced noise that is a direct result of the choice of the AC
frequency. According to exemplary embodiments, the AC voltage can
alternate at a frequency range between about 60 Hz to about 1200
Hz. According to a preferred embodiment, and to minimize the size
and weight of the components, a frequency of about 400 Hz is used
for the AC voltage. A lower AC voltage frequency, for example about
60 Hz, would facilitate production and manufacturing of the self
aligning power transfer system 100, but the size of the components
is inversely proportional to the AC frequency. Also, losses due to
radiated effects increase with lower frequencies, or decrease with
higher frequencies. Although frequencies above 400 Hz could also be
used, as they become smaller components that operate at those
frequencies are generally more expensive and create additional
engineering difficulties.
[0057] According to a further exemplary embodiment, self aligning
power transfer system 100 uses a special semi-permeable magnetic
membrane 336 (FIG. 16) over the surfaces of the primary and
secondary induction coils 303, 301 that efficiently transfers the
magnetic field from the primary induction coil 303 through an air
gap to the secondary induction coil 301 with minimum loss. Self
aligning power transfer system 100 includes a floor mounting
station 102 that houses the primary induction coil 303, and other
components, and that can self-align the primary induction coil 303
to the secondary induction coil 301 in the vehicle 124 as the
vehicle automatically aligns with the floor mounting station 102.
Alignment of the primary and secondary induction coils 303, 301
increases the efficiency of the power transfer from the floor
mounting station 102 (i.e., the primary induction coil 303) to the
vehicle and the secondary induction coil 301.
[0058] Referring back now to FIG. 1, station computer control and
communications module (station module) 132 is linked to one or more
of the other components in floor mounting station 102 by a floor
mounted station data/control computer bus (station bus) 142, and
vehicle computer control and communications module (vehicle module)
134 is linked to one or more of the other components in vehicle
unit 108 by a vehicle unit data/control computer bus (vehicle bus)
148. According to an exemplary embodiment, buses 142, 148 can by
any type of command/control/communication buses commonly used in
the computer industry such as a universal serial bus (USB), a
serial buses, a parallel bus, or any of a multitude of other buses
known for transmitting and receiving commands and/or data.
According to still another exemplary embodiment, station module 132
and vehicle module 134 communicate with each other, either
wirelessly, via an electrical/mechanical connection (i.e., wired
connectors), or a combination of both. If the communication path is
at least partially wireless, it can be in the form of infra-red,
radio-frequency (RF), microwave, laser, light emitting diode (LED),
or even ultra-sonic wireless communications, among other types. In
operation, both station and vehicle modules 132, 134 monitor the
status of the components in their respective units (floor mounted
station unit 102, and vehicle unit 108), and data/information can
be transmitted to the station module 132, which can store the data,
or transmit it to a central unit (not shown) for further processing
and reporting needs. Alternatively, station module 132 collects and
utilizes the collected data to monitor and keep track of the
performance of vehicle 124 as well as the components of vehicle
unit 108.
[0059] According to a preferred embodiment, station module unit
132, through the use of communication devices 135, 137,
automatically aligns station induction coil 303 with vehicle
induction coil 301 through use of feedback control. According to
alternative embodiments, floor mounting station 102 guides the
vehicle into an optimum docking position that is within a range of
control of floor mounting station 102. Station module unit 132
provides indications to the operator of vehicle 124 to affect such
position. Once vehicle 124 has achieved a near alignment position,
station module 132 provides a low level amount of power to station
induction coil 303, and vehicle module unit 134 provides a dummy
load for vehicle induction coil 301 so that its output power can be
measured. The measured output power is then communicated back to
station module unit 132 via communication modules 135, 137, and the
efficiency is measured. Station module unit 132 positions the
station induction coil 303 until a maximum power efficiency is
achieved. Once maximum power transfer efficiency is achieved,
station module 132 provides maximum input power to station
induction coil 303 and vehicle module unit 134 allows the output
power to be sent to vehicle control unit 112 to recharge battery
114. A detailed discussion of automation of the self-alignment
procedure is set forth below.
[0060] Referring now to FIGS. 1 and 3, AC input power 101 enters
floor mounting station 102 and is received by station electronic
power transfer control unit (station control unit) 104. Station
control unit 104 includes circuit breakers 118, and control
contactors 146. Control contactors 146 are simply high power
switches that safely handle switching of high voltage AC such as
240 VAC. The power then enters rectifier and filter unit 120 which
rectifies the input power to produce a direct current voltage and
filters it. According to an exemplary embodiment, rectifier and
filter unit 120 is a full wave rectification device which forms a
better utilization factor of input power than half-wave
rectification devices which are more commonly used for low-power
devices. The filters in the rectifier filter unit 120 reduce high
and low frequencies that might otherwise induce physical and
electrical noise into the self-aligning power transfer system 100
and vehicle 124. Rectifier and filter unit 120 is composed of an
inductive-capacitance (LC) section. Unit 120 may also be a power
factor correcting (PFC) device producing the required DC voltage
for use by the medium frequency inverter 122. Rectifier and filter
unit 120 is preferably a single phase or a three phase bridge
rectifier and filter or PFC in which the 240 VAC, 60 Hz input power
is changed to a direct current (DC) voltage with less than about 5%
ripple for use by medium frequency inverter 122.
[0061] Following rectifier and filter or PFC unit 120 is a medium
frequency inverter 124, which creates a substantially sinusoidal
voltage or square wave voltage with a pre-selected frequency.
According to various embodiments, the pre-selected frequencies of
the input power to vehicle induction coil 301 range from about 60
Hz to about 1200 Hz. Medium frequency as used herein refers to a
range of frequencies in power usage from about 120 to about 1200
Hz. Frequencies below 120 are referred to as low frequencies and
frequencies at or above about 1200 Hz are referred to as high
frequencies. Medium frequency inverter 122 is a full bridge
insulated gate bipolar transistor (IGBT), or MOSFET inverter that
uses four high voltage IGBT's or MOSFET's, two designated as high
side IGBT's or MOSFET's and the other two as low side IGBT's or
MOSFET's. According to a preferred exemplary embodiment, to keep
the total power losses low and the total conversion efficiency
high, medium frequency inverter 122, which can be characterized as
a dc-ac inverter circuit, combines low and high side IGBT's or
MOSFET's to generate a single-phase wave at any frequency between
about 120 and about 1000 Hz. Capacitor 126 and station induction
coil 201, 301 are tuned to substantially maximize power
transfer.
[0062] A power resonant capacitor 126 is connected with the medium
frequency inverter 122. Resonant capacitor 126 effectively supplies
reactive power to the system in the form of a resonant LC circuit
which includes the primary of primary station coil 303.
[0063] Input electrical power enters station induction coil 303
between 100-240 VAC and at medium frequencies and creates a
changing magnetic flux field in the ferro-magnetic core of station
induction coil 303, according to known electromagnetic principles.
The magnetic field flows across an air gap and is coupled to the
ferro-magnetic core of vehicle induction coil 301. The magnetic
field reenters the station induction coil 303 through the air gap
and alternates as the changing input power alternates in a
substantially sinusoidal fashion. As an alternate embodiment,
vehicle induction coil 301 may be a coil composed of conductive
material without a ferro-magnetic core. A resultant output voltage
is produced according to known electromagnetic and transformer
principles.
[0064] As voltage is induced in the vehicle induction coil 301, a
trigger tuning circuit 128, along with silicon controlled rectifier
136, switches in and out circuit capacitor 138, and thereby
controls the voltage regulation of vehicle induction coil output
voltage (induction coil output voltage). Alternatively the
frequency and/or duty cycle of power system 122 is changed to
maintain voltage regulation. A wireless communications system 135
and 137 provides this alternative control feature. Capacitor 138
forms a coil tuning system with the reactance of vehicle induction
coil 301 to substantially maximize power transfer. Induction coil
output voltage is coupled to charger 114 of vehicle 124 through a
transfer switch 130. Transfer switch 130 isolates conduction cable
340 (FIG. 2) from the self aligning inductive power transfer system
100, or isolates self aligning inductive power transfer system 100
from the conductive cables. Battery 116 can then be charged for use
to drive electric engine 144. Conduction cable 340 can be coupled
to vehicle conduction receptacle 106, which carries conducted power
from station unit 108 to vehicle 124, charger 114, and ultimately
battery 116.
[0065] In FIG. 8 is shown a high-noise, low-efficiency power
transfer system (first PTS) 200, using a gapped transformer with an
air gap 221a, 221b between primary induction coil 203 and secondary
induction coil 201.
[0066] It is known in the power transformer arts that a magnetic
field is created when current flows through a conductor. In most
cases, the conductor is a wire, and in the case of a transformer,
the wire is wrapped around a ferro-magnetic core, usually formed of
ferro-magnetic iron. Wrapping the wire causes the magnetic field to
be concentrated within the ferro-magnetic iron core.
[0067] It is further well known that a changing or alternating
magnetic field will induce a charging or alternating current in a
conductor, if that conductor is cut by the changing or alternating
magnetic field. This generally explains how power transformers
operate: a magnetic field is created by the AC input current to the
transformer, the AC magnetic field travels throughout the
ferro-magnetic iron core around which the input power wires are
wrapped, and a voltage is induced on the secondary, or output wires
that are also wrapped around the same ferro-magnetic iron core.
[0068] If first PTS 200, shown in FIG. 8, were built
conventionally, that is, with no air gaps 221a, 221b, then it would
operate as any normal electrical power transformer. However, first
PTS 200 can be used to induce electric power in the form of a
magnetic field across air gaps 221a, 221b such that the electric
power can be transmitted wirelessly to a different location, and no
physical interface (i.e., connectors) is needed to transmit the
electric power. As discussed above, one particular exemplary
embodiment that makes use of such wirelessly transmitted power is
an electric vehicle. Referring again to FIG. 8, first PTS 200
includes secondary induction coil 201 and primary induction coil
203. Secondary induction coil 201 is made up of secondary core 202
and secondary windings 206 and secondary core 202 comprises first
pole 214, with a cross sectional area 224 (FIG. 9), and second pole
216, with a cross sectional area 226. Primary induction coil 203 is
made up of primary core 204, and primary windings 208, and primary
core 204 comprises first pole 218 with a cross sectional area 228,
and second pole 220 with a cross sectional area 230.
[0069] Secondary induction coil 201 is located in vehicle 124 that
requires recharging of its rechargeable batteries 116. As discussed
in greater detail below, primary induction coil 201 is preferably
located in floor mounting station (FMS) 102, or some other suitable
enclosure, and when secondary induction coil 201 is proximately
located relative to primary induction coil 203, an indication will
alert the operator of vehicle 124. The floor mounting system 102
applies a suitable AC voltage to primary input voltage leads
(primary leads) 212a, 212b of the transformer. According to an
exemplary embodiment, floor mounting station 102, which is
discussed in greater detail below, contains suitable logic and
electronic and/or mechanical controls that facilitate switching
on-and-off of power to primary induction coil 203. According to a
preferred embodiment, the logic and control circuitry of floor
mounting station 102 only allows power to be applied to primary
induction coil 203 when secondary induction coil 201 is located at
a close enough distance such that effective proximity inductive
transfer of electrical power can occur.
[0070] As those of ordinary skill in the art can appreciate,
regardless of how close secondary induction coil 201 is located to
primary induction coil 203, an air gap 221a, 221b will exist
between the two poles of the two cores of the two induction coils.
That is, as shown in FIG. 8, air gap 221a exists between first pole
of secondary coil 214 and first pole of primary core 218, and air
gap 221b exists between second pole of secondary coil 214 and
second pole of primary core 218. There is a reactance and
permeability factor that must be taken into account when analyzing
the flow of magnetic fields through open space such as air gaps
221a, 221b. The permeability and reactance of air are fixed
quantities, and for purposes of this discussion, can be presumed to
act as an impedance to the transfer of magnetic fields 232a, 232b
through air gaps 221a, 221b.
[0071] If secondary induction coil 201 is located at the proper
position for effective proximity inductive transfer of electrical
power to occur, floor mounting station 102 provides input power to
primary induction coil 203. When input power it applied to primary
core 204, via primary input voltage leads (primary leads) 212a,
212b, magnetic flux field 232a, 232b exists throughout secondary
core 202 and primary core 204, and through first and second air
gaps 221a, 221b. Because of the air gaps, magnetic field 232a, 232b
will tend to flow in a bulging, outward manner between first pole
218 of primary core and first pole 214 of secondary core, and in a
substantially same manner with respect to second pole of primary
core 220 and second core of secondary core 216. The bulging,
outward flow of magnetic field 232a, 232b reduces the efficient
transfer of electrical energy between primary core 204 and
secondary core 202. As a result, a significantly greater amount of
input power is required for a given amount of output power. For
example, if the efficiency is reduced by 50%, then if 1000 watts of
charging power was required to recharge battery 116 of vehicle 124,
then at least 2,000 watts of power input to primary induction coil
203 would be required. This would necessitate larger windings to
compensate for the additional heat that would have to be dispersed,
as well as greater cooling requirements to dissipate the larger
amounts of heat that would be generated.
[0072] FIG. 9 illustrates a first pole cross sectional surface area
of the secondary core of the gapped transformer as shown in FIG. 8,
and FIG. 10 shows a first core cross sectional surface area of the
secondary core of the gapped transformer of FIG. 8. One reason for
the ineffective transfer of magnetic flux field 232a, 232b across
air gap 221a, 221b is that the ratio of cross sectional area of
first pole 224 of secondary core to the cross sectional area of
secondary winding 223 is substantially unitary, or that is, about
1. An improvement to the design and shape of first PTS 200 is shown
in FIGS. 11-16.
[0073] FIG. 14 illustrates a low-noise high-efficiency power
transfer system (second PTS) 300, using a gapped transformer with
an air gap 321a, 321b between primary induction coil 303 and
secondary induction coil 301 according to a preferred embodiment.
FIG. 11 is a side view of a novel flared C shaped secondary core
302 of second PTS 300 according to an exemplary embodiment, FIG. 12
is a bottom view of the flared C shaped secondary core 302 of
second PTS 300 further illustrating cross sectional area of the
first pole 324 of secondary core and cross sectional area of the
second pole 326 of secondary core, and FIG. 13 is a cross sectional
view along line 13-13 of FIG. 11, showing cross sectional area of
the secondary winding 323 of secondary core 302 of second PTS 300.
FIG. 15 is a front perspective view of the secondary C shaped
secondary core as shown in F. 11. According to an exemplary
embodiment, first pole 314 of secondary core 302 and second pole of
secondary core 302, as shown in FIG. 15, are notably larger than
first pole 214 of secondary core 202 and second pole of secondary
core 202 of first PTS 200. The shape of secondary core 302 (and
similarly, primary core 304) is preferably a C shape with flared
portions at the top and bottom portions of the C. This flaring
provides a larger surface area for magnetic field 332a, 332b to
flow through and into, and which leads directly to the increased
efficiency and low noise effects of second PTS 300.
[0074] The relative permeability of iron is generally in the
thousands and there is a direct relationship between the
permeability value and the ability of the magnetic field to flow.
Thus, the higher the permeability, the easier the magnetic field
will flow. That is why most transformers are fabricated from iron.
Conversely, the lower the permeability, the less able the magnetic
field can flow. Air is generally thought to have a relative
permeability value of about 1. Therefore, any air gap between the
primary and secondary cores 202, 204; 302, 304, will negatively
affect the ability of the magnetic field to flow. In other words,
the magnetic field will flow thousands of times better in the iron
than through the air.
[0075] Second PTS 300 comprises vehicle (secondary) induction coil
301, and station (primary) induction coil 303. Secondary induction
coil 301 includes secondary core 302 and secondary windings 306,
and secondary core 302 comprises first pole 314 with a cross
sectional area 324, and second pole 316 with a cross sectional area
326. Primary induction coil 303 includes primary core 304, and
primary windings 308, and primary core 304 has a first pole 318
with a cross sectional area 328 and a second pole 320 with a cross
sectional area 330.
[0076] Operation of second PTS 300 is similar to that of first PTS
200. Notably however, the ratio of cross sectional area of first
pole of secondary core 324 (seen in FIG. 12) to cross sectional
area of secondary winding 323 (seen in FIG. 13) is between about
2.0 to about 5.0. Preferably, the ratio of cross sectional area of
first pole of secondary core 324 to cross sectional area of
secondary winding 323 is about 3.2. Increasing the ratio of the
area of the pole area to the winding area of secondary core 302 and
primary core 304 leads to magnetic field 332a, 332b being
substantially contained within a volume of space essentially
defined by the boundaries of the pole areas of the cores as seen in
FIG. 14.
[0077] The flux density of the magnetic field is directly
proportional to the area of the iron that the magnetic field is
traveling through. In the air gap between primary and secondary
cores 302, 304, the low permeability of the air acts as an
impediment to the flow of the magnetic field. As a result an
increase in fringing occurs. The magnetic field seeks a different
path through which to flow, and therefore diverges greatly from its
intended path, straight across the air gap. It has been determined
that if the flux density can be decreased in that the air gap area
by increasing the pole area relative to the cross sectional area of
the winding area, then the amount of fringing is decreased
dramatically, and more of the magnetic field finds its way across
the air gap. Thus, the overall charging efficiency of the second
PTS increases substantially. The ratio of the pole cross sectional
area to that of the winding cross sectional area is preferably
about 3.2.
[0078] As a result of the increase in ratio of pole to winding
areas, a greater majority of magnetic flux 332a, 332b is contained
and can flow unimpeded between secondary core 302 and primary core
304 and the power transfer efficiency between the power input to
primary core 304 and power output from secondary core 302 increases
to between about 80% to about 95%. According to a preferred
embodiment, the power transfer efficiency is about 90%.
[0079] At least one additional benefit is derived from the flared C
shape of secondary and primary cores 304, 302 of second PTS 300:
induced noise is reduced dramatically. As discussed in greater
detail above, a preferred frequency for the AC voltage is within
the medium range of frequencies on the order of 400 Hz. Use of a
medium frequency inverter 122 reduces the size of the components.
In addition, use of frequencies in the medium range is widely used
in the aircraft industry, and therefore power supply/transformer
components are readily available and competitively priced. One
drawback to medium frequencies is that they are substantially close
to a pure "A" note (440 Hz) and are most discernable, in a negative
manner, even in very noisy environments.
[0080] Second PTS 300 substantially reduces inducted noise by
containing magnetic field 232a, 232b, as discussed in greater
detail below, within the larger area of its poles 314, 316, 318,
and 320. As a result, inducted oscillations of different components
of self-aligning PTS 100 and vehicle 124 were reduced, on the order
of at least several decibels (dB's). According to an exemplary
embodiment, induced noise was reduced between a first range of dB's
and induced noise was reduced between a second range of dB's.
[0081] The pole areas 214, 216, 218, and 220 of vehicle core 202
and station core 204 need not be substantially flat, as FIGS. 17
and 18 illustrate. As discussed above, increasing the ratio of area
between the pole and winding sections of the core increases the
capability of magnetic flux field 232 to travel across air gaps
221a, 221b. The ratio of area can be increased without altering the
overall dimensions of pole areas 214, 216, 218, and 220 of vehicle
core 202 and station core 204, as shown in FIG. 17. In FIG. 17,
which is a front view of vehicle core 202 and station core 204
according to an alternate exemplary embodiment, the outer
dimensions of the pole sections remain the same as shown in FIGS.
11-15, but the surface area, the cross sectional area of the first
and second poles of the vehicle core 202 and station core 204 has
increased substantially because of the modified U shape of the pole
surfaces. The ratio of area of the pole to core winding areas now
increases by a first percentage. Other configurations are possible.
Such alternative configurations of the pole surfaces will
necessitate a modified approach to docking between vehicle 124 and
floor mounting station 102 as will be discussed in greater detail
below.
[0082] Referring now to FIGS. 17 and 18, an alternate embodiment of
the core pole areas is shown. As discussed above, adding area to
the first pole of secondary core 214 and first pole of primary core
218 permits an easier flow of magnetic flux field 232 across the
small gap between vehicle core 202 and station core 204,
substantially increasing its efficiency and substantially
decreasing induced noise/hum in vehicle 124. The arrangement of
pole areas 214' and 218' increases the surface area because of the
trapezoid extension and recess formed in the two cores 202, 204.
Similarly, the extension and recess could be square, triangular,
circular, oval, parabolic or any of a multitude of shapes. Each
such change in configuration adds more surface area than if a flat
surface were used, with the length and width constraints of the
cross-sectional area of the winding 222. By way of example only,
for a square extension and recess as shown in FIGS. 19 and 20, and
expressing the same in percentages of length and width, an increase
in area of 60% can be obtained.
[0083] Some gap between the cores 302, 304 is desirable to prevent
them from sliding across each other and thereby causing undue wear
to the surface of each core. The larger the gap 221a, 221b, the
less efficient will be the transfer of magnetic fields 232a, 232b
between the cores 302, 304. The magnetic fields 232a, 232b tend to
fan out at the edges of cores 302, 304 across gaps 221a, 221b, as
shown in FIG. 8. To reduce or alleviate this issue, and increase
the efficiency of the system, the cores 302, 304 are substantially
coated with a semi-permeable resin or epoxy material in the form of
a semi-permeable magnetic membrane 336 that includes a magnetic
material embedded therein. In one implementation, the magnetic
material embedded within the resin or epoxy material is a
ferromagnetic material, such as iron or steel.
[0084] FIG. 17 shows a view of vehicle induction coil 301 as would
be seen by station induction coil 303. Although only vehicle
induction coil 301 is shown, a similar arrangement would be used
for station induction coil 303. Secondary core 302 includes
secondary winding 306 as discussed above. First and second poles
314, 316 are coated with the semi-permeable magnetic membrane
336.
[0085] The semi-permeable magnetic membrane 336 forms a hermetic
coating over first and second poles 314, 316 to prevent corrosion.
Semi-permeable magnetic membrane includes a ferromagnetic material
337 such as iron or steel filings embedded therein. Ferromagnetic
material 337 may be formed of powdered transformer steel or similar
material. Ferromagnetic material 337 is mixed into an epoxy binder
and applied to first and second poles 314, 316 to form the
semi-permeable magnetic membrane 336.
[0086] Ferromagnetic material 337 generally comprises about 30% to
90% or more of the semi-permeable magnetic membrane 336. In
general, less than about 30% of ferromagnetic material 337 would
not sufficiently increase efficiency, while greater than about 75%
may become brittle. In one implementation, semi-permeable magnetic
membrane 336 includes 71% powdered iron as the ferromagnetic
material 337.
[0087] When implemented as powdered iron, a general implementation
would include a distribution of sizes of the individual granules.
The distribution includes about 70% to 75% being +325 mesh, less
than about 16% being +100 mesh, with the balance of up to about 30%
pan sieve. In one example, iron powder size distribution is as
follows:
TABLE-US-00001 +60 Mesh US Std Sieve 0.0 wt % +100 Mesh US Std
Sieve 10.3 wt % +325 Mesh US Std Sieve 72.0 wt % +Pan Sieve 17.7 wt
%
[0088] There are several types of resins or epoxies that can be
used with specific formulations. Furthermore, the filings can be
aligned or they can be placed randomly. There are several sizes of
the filings, several methods of preparation, and several methods of
applying the semi-permeable magnetic membrane to the poles.
[0089] The semi-permeable magnetic membrane 336 is applied to both
primary core 304 and secondary core 302 to fill the gap between the
cores 302, 304. Semi-permeable magnetic membrane 336 reduces
friction on each core when they come into contact, thereby saving
wear on the cores 302, 304. Ferromagnetic material 337 embedded in
semi-permeable magnetic membrane 336 permits an appreciable
increase in transfer of the magnetic field and therefore the power
transfer efficiency. A 24 V drop was noted without use of
ferromagnetic material 337 in semi-permeable magnetic membrane
336.
[0090] FIGS. 22A and 22B illustrate a first decrease in the
fringing of magnetic flux field 232 when a semi-permeable magnetic
membrane 336 is used with first power transformer 200 according to
one embodiment, and FIGS. 23A and 23B illustrate a second decrease
in fringing of magnetic flux field 332 when a semi-permeable
magnetic membrane 336 is used with second power transformer 300.
FIGS. 22A and 22B illustrate the effect of use of membrane 336 with
secondary core 202 and primary core 204. In FIG. 22A, there is no
membrane 336 and there is significant fringing of magnetic flux
field 232 as discussed in detail above. In FIG. 22B, membrane 336
(not drawn to scale) is added to the first pole of primary core 218
and the first pole of secondary core 214, and magnetic flux field
232a' is significantly reduced. The reduction in magnetic flux
field 232a' is between about a first range, and the reduction in
magnetic flux field 232a' is about a second percentage.
[0091] FIGS. 23A and 23B illustrate the effect of membrane 336 with
secondary core 302 and primary core 304. In FIG. 23A, there is no
membrane 336 and there is significant fringing of magnetic flux
field 332 as discussed in detail above. In FIG. 23B, membrane 336
(not drawn to scale) is added to first pole of primary core 318 and
first pole of secondary core 314, and magnetic flux field 332a' is
significantly reduced. According to an exemplary embodiment, the
reduction in magnetic flux field 332a' is between about a second
range, and according to a preferred embodiment, the reduction in
magnetic flux field 332a' is about a third percentage.
[0092] Referring now to FIG. 24, there is shown a floor mounting
station (FMS) 102 that can be used with either of the first or
second self or automatic aligning power transfer system 100, 200
according to a preferred embodiment of the present invention. As
briefly discussed above, floor mounting station 102 can
automatically self-align itself to vehicle 124 when an operator of
vehicle 124 approaches the floor mounting station 102 to begin
recharging battery 116. Self-aligning of floor mounting station 102
is accomplished by a three quadrant operating mechanism supported
by a plurality of springs, slides, enclosures and rollers that
allows interface plate 406a of floor mounting station 102 to freely
and independently move in lateral, longitudinal and vertical
directions as vehicle 124 moves in proximity to the floor mounting
station 102. Status indicator lights on tower 402 of floor mounting
station 102 indicate several different statuses of floor mounting
station 102, and proximity sensors allow charging to begin when
vehicle 124 is in the proper position.
[0093] The floor mounting station 102 includes tower 402,
indicators 140a-d, floor mounting fixture 404, interface plate 406a
having a guide plate 408 thereon, station unit enclosure 410, front
mounting receptacles 416, rear mounting receptacle 418, indicator
panel 420, springs 422, plate anchor 430, and inner enclosure 414,
among other components. The FMS 102 further includes electronics
enclosure 150, and station unit communication device 137.
Electronic enclosure 150 houses station control unit 104. First or
second power transfer systems 200, 300 that are part of floor
mounting station 102 (and not part of vehicle 124), and station
unit communication device 137 are generally housed in station unit
enclosure 410. Also shown as part of floor mounting station 102 are
certain components of first power transfer system 200 and second
power transfer system 300, for example, primary induction coil 203,
303, hermetic epoxy sealing case 334, and semi-permeable magnetic
membrane 336.
[0094] As seen in FIGS. 24-32, floor mounting station 102 is
generally a rectangular shaped device with a low profile and a
column-like tower 402. Tower 402 needs only be tall enough such
that it can reasonably be seen by an operator of vehicle 124 which
is to be positioned relative to the system. The station unit 102
and first and second power transfer system 200, 300 are designed to
accommodate different brands of motor vehicles or other types
electrically powered devices to be recharged. Moreover, the
position of the tower 402 on floor mounting station 102 can be
changed as necessary to accommodate different vehicles as FIGS. 6
and 24 illustrate. In FIG. 24, tower 402 is centrally located on
floor mounting station 102 whereas in FIG. 6, tower 402 is located
along a left side of floor mounting station 102 as viewed by an
operator of vehicle 124 and is therefore substantially directly in
front of the vehicle operator. In this case, according to a
preferred embodiment, vehicle 124 is an automobile, and the
location of tower 402 greatly improves docking so that near perfect
alignment is achieved.
[0095] As seen in FIG. 24, interface plate 406a resides on an upper
portion of station unit enclosure 410, and houses the station unit
components of first and second power transfer system 200, 300,
which includes primary induction coil 203, 303, and hermetic epoxy
sealing case 334, and semi-permeable magnetic membrane 336. FIG. 25
is a top view of the floor mounting system as shown in FIG. 24.
While the second power transfer system 300 and its components will
be described, both first and second power transfer system 200, 300
are substantially interchangeable, and both can be used with the
different exemplary embodiments of floor mounting station 102 as
discussed herein.
[0096] Vehicle induction coil 301 is mounted on the vehicle 124 and
positioned in such a way as to be able to get as close as possible
to station induction coil 303 on the interface plate 406a of the
station 102 when recharging is desired. The induction coil 303 is
mounted to first interface plate 406a such that first and second
poles of primary core 318, 320 are flush with an upper surface of
first interface plate 406a as shown in FIGS. 24, 25, and 27. First
and second poles of station core 318, 320 and first and second
poles of vehicle core 314, 316 are covered with semi-permeable
magnetic membrane 336 to facilitate transfer of electric power
inductively from station unit 102 to vehicle 124. When the vehicle
124 is properly positioned with respect to the station unit 102,
the semi-permeable magnetic membranes 336 of first and second poles
of station core 318, 320 and first and second poles of vehicle core
314, 316 may be very close together or touching each other. At such
a positioning between vehicle 124, floor mounting station 102, the
first and second poles of station core 318 and first and second
poles of vehicle core 314, 316 are in magnetic conjunction so that
a substantially efficient transfer of electrical power can take
place between floor mounting station 102 and vehicle 124.
[0097] Referring now to FIGS. 26, 27, and 28, FIG. 26 is a front
cut-away perspective view of floor mounting station 102 as shown in
FIG. 24, FIG. 27 is a cut-away side view of floor mounting station
102, and FIG. 28 is a partial cut-away side view of floor mounting
station 102. FIG. 26 illustrates a pair of front mounting
receptacles 416a, 416b which provide a mounting location for
springs 422a, 422b as shown in FIGS. 27 and 28 which are then
attached on a lower surface of first interface plate 406a. For
purposes of this discussion, reference shall be made to an upper
and lower surface of first interface plate 406a where the upper
surface is that surface located closest to vehicle 124 and the
lower surface is that surface located closest to or within station
unit enclosure 410. A top portion of first interface plate 406a is
that portion of first interface plate 406a that is closest to tower
402 and a lower portion of first interface plate 406a is that
portion of first interface plate 406a that is located farthest away
from tower 402, and to which is attached rear mounting receptacle
418 as shown in FIGS. 27 and 28. It will be appreciated that while
two mounting receptacles are shown, other configurations will work
equally well.
[0098] In operation, station unit 102 allows the vehicle induction
coil 301 to come in as close proximity as possible to station
induction coil 303. To facilitate a sufficient proximity of vehicle
induction coil 301 and station induction coil 303, station unit 102
is constructed such that first interface plate 406a retains station
induction coil 303 at plate inclination angle .theta.. Preferably,
the plate inclination angle .theta. is a relatively shallow or
small angle such that a smooth almost frictionless interface exists
between vehicle induction coil 301 and station induction coil 303.
Use of springs 422a, 422b at first and second mounting receptacles
416a, 416b provide first interface plate 406a with the ability to
rotate about rear mounting receptacle 418 in the direction of arrow
A as shown in FIG. 27, such that as vehicle 124 and vehicle
induction coil 301 encounter station unit 102 and station induction
coil 303, first interface plate 406a gently rotates downwardly.
Springs 422a, 422b push first interface plate 406a with station
induction coil 301 gently upwardly, so that station induction coil
303 and vehicle induction coil 301 can make sufficient contact
while substantially minimizing shock, vibration, and mechanical
damage.
[0099] Also shown in FIG. 27 is an electronics enclosure 150 which
houses station control unit 104 which is electrically connected to
station induction coil 303. The electronics are electrically
connected or wirelessly connected to indicators 140 and/or
indicator panel 420. Station unit enclosure 410 is fixed to the
floor or ground via floor mounting fixture 404 and bolt 432.
[0100] As discussed above, first interface plate 406a can rotate
about rear mounting receptacle 418 in the direction of arrow A,
because first interface plate 406a is mounted to rear mounting
receptacle 418 via a pin that can rotate as shown by arrow B.
Referring now to FIG. 28, it can be seen that rear mounting
receptacle 418 can also rotate in the direction of arrow C which
further allows rotation of first plate 406a in the direction of
arrows D and E as shown in FIG. 28. Springs 422a, 422b allow the
first plate 406a to rotate in the direction of arrows D and E, but
such rotation would be constrained with the use of rotating rear
mounting receptacle 418. According to an alternate embodiment, rear
mounting receptacle 418 can be replaced with spring 422 and still
operate in a substantially similar manner. Thus, the combination of
rotating rear mounting receptacle 418 and front mounting
receptacles 416a, 416b with springs 422 provides first interface
plate 406a with the means to move in two dimensions: up and down as
shown by arrow A in FIG. 27 and to the left and right as shown by
arrows D and E, in FIG. 28 in order to self-align the station
induction coil 303 on the first interface plate 406a with the
vehicle induction coil 301.
[0101] Attention is now directed to FIGS. 29 and 30. FIG. 29 is a
partial top view of vehicle 124 approaching floor mounting station
102 as shown in FIG. 24, and FIGS. 30A and 30B illustrate angles of
approach between vehicle 124 and floor mounting station 102 as
shown in FIGS. 24 and 29. As discussed above, the combination of
rotating rear mounting receptacle 418 and front mounting
receptacles 416a, 416b with springs 422 provides first interface
plate 406a with the means to move laterally and vertically in order
to self-align first interface plate 406a and station induction coil
303 with vehicle induction coil 301. Self-alignment, however, is
accomplished by interaction between vehicle induction coil 301 as
it approaches station unit 102 and self-align first interface plate
406a so that vehicle induction coil 301 and station induction coil
303 are proximately close together. Plate guide 408 comprises left
plate guide arm 409a, right plate guide arm 409b, and plate guide
back wall 411. Both first and second plate guide arms 409a, 409b
are formed at a plate guide angles .PHI..sub.1,2 with respect to
plate guide back wall 411. As discussed in greater detail below,
the length of first and second plate guide arms 409a, 409b and
plate guide angle .PHI. directly determine the limitations in terms
of distances in which self-alignment can still occur.
[0102] Various design considerations are taken into account in the
design of plate guide 408, the length of plate guide arms 409a,
409b, and the angles of left and right plate guide arms 409a, b. If
plate guide angle .PHI. is too large and/or the length of plate
guide arms 409a, 409b is too long, then there will not be enough
range of motion in springs 422 and rear mounting receptacle 418. In
other words, if plate guide angle .PHI. is too large, vehicle 124
can approach floor mounting station 102 at too large of an angle
for first interface plate 406 to compensate for self-alignment, and
it will not occur. Moreover, limiting plate guide angle .PHI. means
that there is a limitation on the angle that vehicle 124 can make
in approaching first interface plate 406, which is referred to as
approach angle .OMEGA.. Approach angle .OMEGA. is shown in FIGS.
30A, and 30B.
[0103] As seen in FIG. 30A (which shows only enough detail of floor
mounting station 102 necessary for an explanation of approach angle
.OMEGA.), if vehicle 124 is approaching such that it is to the left
of station unit 102, the left-front corner LF of vehicle induction
coil 301 will be aligned just to the right or inner part of the
end-most portion of left plate guide arm 409a. If vehicle 124 was
any further to the left of station unit 102, a front portion of
vehicle induction coil 301 would impact left plate guide arm 409a,
and no self-alignment could take place. A similar situation occurs
when vehicle 124 approaches from the right side of station unit 102
wherein, as shown in FIG. 30B, the right-front corner RF of vehicle
induction coil 301 will be aligned just to the left, or inner, part
of the end-most portion of right plate guide arm 409b
[0104] FIG. 31 is a partial top view of an alternate embodiment of
the second interface plate 406b that is used with first and second
power transfer system 200, 300 and FIG. 32 is a side view of second
interface plate 406b. Second interface plate 406b operates in a
manner similar to first interface plate 406a, and all other
components of floor mounting station 102 not shown in FIGS. 31 and
32 are substantially the same as discussed above. Second interface
plate 406b differs from first interface plate 406a in that it is
connected to enclosure upper surface 412a, 412b and not to the
inner floor surface of station unit enclosure 410 by several
springs 422 and plate anchors 430 as shown in FIG. 31. The
arrangement of plate anchors 430 and springs 422 and their
connection to second interface plate 406b provides second interface
plate 406b with the ability to move in three dimensions and to
rotate as shown in FIGS. 31 and 32. However, even with additional
degrees of movement, there are limitations on the angles of
movement and the approach angle of vehicle 124 as discussed above
with respect to the first interface plate 406a. That is, there is a
plate guide angle, now referred to as second plate guide angle
.PHI., and there is an approach angle .OMEGA., now referred to as
second approach angle .OMEGA..
[0105] Tower 401 contains indicators 140a-d and an indicator panel
420 that houses indicators 140a-d as shown in FIG. 27. Indicators
140a-d can be one or more of many different types of colored
indicators such as light emitting diodes (LEDs), incandescent
bulbs, florescent bulbs, neon lamps, plasma panels, light
commanding diodes (LCDs), fiber optic cables, or even
white/clear-colored indicators, with colored plastic or glass
coverings.
[0106] By way of example, indicator 140a can be colored red and
indicates "STOP", meaning that vehicle 124 is in position.
Indicator 140b can be colored yellow to indicate "CHARGING",
meaning self aligning power transfer system 100 is charging vehicle
124. Indicator 140c is colored green and indicates "READY", meaning
floor mounting station 102 and vehicle unit 108 have communicated
with each other and that self aligning power transfer system 100 is
ready to begin charging. Indictor 104d can be colored blue to
indicate "STOPPED CHARGING", meaning that charging is completed. Of
course, the colors and messages/meanings can be altered and
configured to fit specific situations, and/or design choices
[0107] Not shown but part of station unit 108 is a proximity
detector which can be a separate sensor or a particular function
that is carried out by station communication module 134 and vehicle
communication module 132. Proximity detection determines when
vehicle 124 is in position and ready to accept electrical power.
The proximity detector also determines when vehicle 124 has pulled
away from or is no longer in close proximity to station unit 108 so
that if charging is still occurring, controls can be implemented to
turn off power to station induction coil 203, 303.
[0108] Communications between the vehicle 124 and the self-aligning
power transfer system 100 can take the form of wireless
communications such as via radio frequency (RF) or microwave
frequencies (or higher), infra-red, laser, and ultra-sonic signals
or in a wired fashion by a physical connection between vehicle 124
and vehicle unit 108, and floor mounting station 102.
Communications and other electrical specifications are discussed in
greater detail in "Surface Vehicle Recommend Practice," published
by The Engineering Society for Advancing Mobility Land Sea Air and
Space, Society of Automotive Engineers (SAE), document J1772,
issued in October of 1996, rev. November 2001 and the "2008
National Electrical Code Handbook," Article 625, "Electric Vehicle
Charging System," both of which are incorporated herein by
reference.
[0109] FIG. 33 is a flow diagram of method 500 illustrating
operation of the self-aligning inductive AC power transfer system
100 according to another embodiment. Method 500 begins when vehicle
124 pulls into a parking spot, and engages floor mounting station
102. In decision step 502, one or more sensors determine proximity
of vehicle 124 and communicates that the vehicle 124 has properly
mated with self-aligning power transfer system 100 ("Yes" path from
decision step 502). Stop indicator 140a is lit (step 504).
Alternatively, if vehicle 124 has not properly mated with
self-aligning power transfer system 100, decision step 502 prevents
stop indicator 140a from lighting (step 506, "No" path from
decision step 502). Method 500 continues to check the proximity
detector function, until proximity is detected. Following decision
step 502, method 500 proceeds to decision step 508, and the balance
of the flow chart.
[0110] FIG. 7 is a system architecture block diagram 600 for the
self-aligning inductive AC power transfer system 100 according to a
further embodiment. Substantially all of the components shown in
FIG. 7 have been discussed in greater detail above, and therefore
shall not be repeated again. However, there are some components of
system architecture 600 that have not been addressed. For example,
additional inputs 602a-j to station computer 132 can be
incorporated into self-alignment power transfer system 100. A
non-exhaustive list of additional inputs can further include
proximity detect 602a (discussed above), charge current 602b, stop
button 602c, over travel limit 602d, station pole over-temperature
602e, heat sink over-temperature 602f, infra-red system status
602g, station pole proximity detect 602h, pilot voltage 602i, and
load shed 602j. Additional outputs can be produced by vehicle
computer 134 for use by self-alignment system 100 and for
observation by an operator of self-alignment power transfer system
100. These include, for example, system ready light 604a (discussed
above), stop light 604b (discussed above), charging light 604c
(discussed above), safety contactor 604d, P2 generation 604e, pilot
voltage pulse width 604f, and station plug transfer switch 604g,
among others.
[0111] Charge current 602b can be an input to station computer 132
to monitor and track the amount of current that is being
transferred to vehicle 124. A separate charge current can also be
monitored by vehicle computer 134 and the two values can be
compared. Over travel limit 602d can be detected by station
computer 132 to detect when vehicle 124 is misaligned with station
unit 102. Station pole over-temperature 602e is an indication of
the temperature of either one or both of first and second poles of
primary and/or secondary cores 314, 316, 318, 320. Heat sink
over-temperature 602f is an indication of the temperature of a heat
sink for one or both of vehicle core 302 and station core 304, or
of station unit 102 itself. Infra-red system status 602g is an
induction of the operating status of vehicle and station
communication devices 137, 136 respectively. Station pole proximity
detect 602h is an indication of proximity between one or both first
and second poles of secondary core 314, 316 with first and second
poles of primary core 318, 320.
[0112] Additional outputs can be produced for observation by an
operator of self-alignment power transfer system 100. These can
include, for example, system ready light 604a, stop light 604b, and
charging light 604c.
[0113] FIG. 34 is a block diagram of a multiple-user floor mounted
station system 700 according to an exemplary embodiment. Multiple
floor mounted system 700 allows multiple users to charge their
vehicles or other devices that use rechargeable batteries 116,
simultaneously. Thus, for example, multiple floor mounted station
system can be used at parking lots and garages, convenience stores,
shopping centers, malls, and housing developments, among other
places. Vendors can charge user fees for recharging vehicles and an
appropriately designed user interface that takes different modes of
payments (cash, credit cards, electronic tag systems) could be used
to collect the user-charging fees.
[0114] Multiple floor mounted station system 700 can simultaneously
charge one or more vehicles 124 at a time. The multiple charging
system 700 operates similarly to a stand-alone charging system 102.
As shown in FIG. 34, there are several floor mounted stations 102
interconnected by AC input power 101, and intra-floor mounted
station communication cable 152. Each individual floor mounted
station 102 operates similarly to that as described above, except
that with two or more floor mounted stations 102 connected together
in the configuration of multiple floor mounted station system 700
as shown in FIG. 34, one of the multiple stations 102 must be
designated a master and the rest as slaves. The master floor
mounted station 102 of multiple floor mounted station system 700
can communicate with its slaves either wirelessly or through a
wired communication cable 152, as shown in FIG. 34 using RS232,
USB, or other types of communication. Communication can be
performed from the master to all slaves and visa-versa, or from the
master to slave 1, then from slave 1 to slave 2, and so on. In
either case, the master floor mounted station 102 must be informed
of all of the slave floor mounted stations 102 that it is
responsible for, and this can be done manually via switches or
electronically. For example, there can be a protocol built into
floor mounted station 102 that when communication cable 152 is
hooked into a first station 102, it automatically begins searching
for other stations 102 and attempts to determine which one is the
master.
[0115] The master floor mounted station 102 of the multiple system
700 collects data for billing and/or maintenance purposes and can
communicate with a base station by cellular, internet or other
landline/wireless communication system. The master floor mounted
station of the multiple station system 700 controls current load
distribution between and among its slaves. By way of example,
assume that there are 10 stations 102 in a multiple floor mounted
station system 700, each providing a total of 50 Amps current for
recharging. However, the electrical service that multiple station
system is connected to is rated only for 400 Amps. If ten vehicles
are simultaneously recharging, the maximum current load for the
electrical circuit will be exceeded, and either the breaker will
trip, or a catastrophic failure and fire could result. According to
the invention, the master floor mounted station 102 can detect that
the tenth vehicle is ready to begin charging and can communicate to
its slaves to decrease their respective output charging current to
40 Amps (or less) until further notified. Information about each
slave's charging current is automatically communicated to the
master, or the master can periodically request status updates, or a
combination thereof can occur. As soon as one of the slave's
vehicle discontinues charging, the master station 102 authorizes
maximum charging current from the balance of the slave stations. A
preferential payment system can be implemented that allows a user
to pay more for the express purpose of receiving a maximum charging
current from its charging station 102 even if the charging current
provided by other stations 102 are severely degraded.
[0116] There are several advantages to the design and
implementation of self-alignment power transfer system 100
according to the various embodiments discussed herein. For example,
it is advantageous to provide inductive power transfer to a vehicle
that is universal in nature, and wherein the voltage ratio of the
station and vehicle unit is matched to supply the proper charging
voltage and power required by the vehicle.
[0117] A further advantage is to eliminate the problems associated
with handling dirty, wet, dangerous frayed cords and exposed live
contacts since there are no live contacts which the operator can
access. The invention provides a very convenient method of
inductive power transfer that requires that the operator need only
to drive up to and over a self-aligning station unit to initiate
power transfer. Coupling of the vehicle with the charging station
is safe and tamper proof while power is transferred to the vehicle.
The invention further provides high power, high efficiency, low
audible noise power transfer to the vehicle that is durable,
reliable and economical. This is accomplished by the use of a
transformer gap composed of semi-permeable magnetic material.
[0118] While the preferred forms and embodiments of the present
invention have been illustrated and described, it will be readily
apparent to those skilled in the art that various changes and
modifications may be made without deviating from the inventive
concepts set forth above.
* * * * *