U.S. patent application number 11/355969 was filed with the patent office on 2006-06-29 for power transfer switch assembly.
Invention is credited to David Langham, Paul C. Wareham.
Application Number | 20060138868 11/355969 |
Document ID | / |
Family ID | 23212908 |
Filed Date | 2006-06-29 |
United States Patent
Application |
20060138868 |
Kind Code |
A1 |
Wareham; Paul C. ; et
al. |
June 29, 2006 |
Power transfer switch assembly
Abstract
A modularly attachable transfer switch assembly for operative
connection to two alternate power sources and a power load is
disclosed. The transfer switch can be quickly and easily installed
upon existing electrical meters and therefore does not require
modifications to existing electrical wiring systems. The transfer
switch includes one power switch for selectively connecting a
electrical utility power supply to the power load of a structure,
such as a building for example, and a second power switch for
selectively connecting an emergency power supply to the power load
of the building. The transfer switch includes a mechanical
interlock operatively connected to both the power switches for
physically preventing both the power switches from assuming
simultaneous ON positions, and a controller for controlling the
emergency power supply and the transfer switches. The transfer
switch is enclosed within a casing adapted for connection between a
watt-hour meter and a meter socket of existing service
installations for simple installation of the transfer switch.
Inventors: |
Wareham; Paul C.; (Sydney,
CA) ; Langham; David; (Sydney, CA) |
Correspondence
Address: |
BORDEN LADNER GERVAIS LLP
WORLD EXCHANGE PLAZA
100 QUEEN STREET SUITE 1100
OTTAWA
ON
K1P 1J9
CA
|
Family ID: |
23212908 |
Appl. No.: |
11/355969 |
Filed: |
February 17, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10219300 |
Aug 16, 2002 |
7030514 |
|
|
11355969 |
Feb 17, 2006 |
|
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|
60312765 |
Aug 17, 2001 |
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Current U.S.
Class: |
307/126 |
Current CPC
Class: |
H02J 9/066 20130101;
H02J 9/068 20200101; H02J 9/06 20130101; H02J 9/061 20130101; H02J
9/08 20130101; H01H 2300/018 20130101 |
Class at
Publication: |
307/126 |
International
Class: |
H02H 3/42 20060101
H02H003/42 |
Claims
1. A power transfer switch assembly modularly attachable to a
service installation, for selectively connecting one of a main
power supply and an alternate power supply to a power load
comprising: a first power switch including a mechanical switching
device for actuating the mechanical switching elements between an
ON state and an OFF state, for receiving the main power supply and
for coupling the main power supply to the power load in the ON
state; a second power switch including a mechanical switching
device for actuating the mechanical switching elements between an
ON state and an OFF state, for receiving the alternate power supply
and for coupling the alternate power supply to the power load in
the ON state; a mechanical interlock having a locking actuator
mechanically coupled to the first and the second power switches for
physically preventing the first power switch and the second power
switch from assuming simultaneous ON states; a controller for
monitoring the main power supply and switching the first power
switch to the OFF state and the second power switch to the ON state
when a disturbance in the main power supply is detected, the
controller switching the second power switch to the OFF state and
the first power switch to the ON state when the main power supply
is restored; and, a casing containing the first power switch, the
second power switch, the mechanical interlock and the controller,
the casing having load terminals and line terminals for connection
with a meter socket of the service installation, and line out and
line in feed terminals for connection with a watt-hour meter of the
service installation, the load terminals being connected to the
first and second power switches, the line terminals being connected
to the line out feed terminals, and the line in feed terminals
being connected to the first power switch.
2. The power transfer switch assembly of claim 1, wherein the
casing receives the main power supply from the line terminals and
the alternate power supply from a cable.
3. The power transfer switch assembly of claim 1, wherein the
controller includes a remote communication system for exchanging
information of a status of the switch, giving position, generator
status and normal supply status with a remote interface unit.
4. The power transfer switch assembly of claim 3, wherein the
remote communication system includes hard wired twisted pair
communications cable.
5. The power transfer switch assembly of claim 3, wherein the
remote communication system includes a power line communications
modem.
6. The power transfer switch assembly of claim 3, wherein the
remote communication system includes a wireless radio frequency
modem.
7. The power transfer switch assembly of claim 3, wherein the
remote interface unit includes a stand-alone user interface
display.
8. The power transfer switch assembly of claim 3, wherein the
remote interface unit includes a personal computing device.
9. The power transfer switch assembly of claim 8, wherein the
personal computing device includes a personal computer.
10. The power transfer switch assembly of claim 8, wherein the
personal computing device includes a personal digital
assistant.
11. The power transfer switch assembly of claim 1, wherein the
mechanically-held device is a solenoid.
12. The power transfer switch assembly of claim 1, wherein the
locking actuator has a pair of L-shaped tabs that are in sliding
engagement with the body of the mechanical interlock.
13. The power transfer switch assembly of claim 1, wherein the
locking actuator has a U-shaped bracket having its ends secured to
the bodies of both power switches.
14. The power transfer switch assembly of claim 1, wherein the
locking actuator is a rocking bar pivotally connected to the walls
of the U-shaped bracket through a central pivot and the ends of the
rocking bar are in contact with a respective a actuator pin.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of co-pending U.S. patent
application Ser. No. 10/219,300, filed Aug. 16, 2002, which claims
priority from U.S. provisional patent application Ser. No.
60/312,765, filed Aug. 17, 2001, the contents of which are
expressly incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to electrical switching
assemblies. In particular, the present invention relates to
transfer switch assemblies for interconnecting power to a building
from two alternate power supplies.
BACKGROUND OF THE INVENTION
[0003] Customers of electric utility companies often desire a
back-up electrical power supply during a power outage. Typically,
such a back-up is provided by an alternate power supply such as a
fuel-fired engine-driven power generator, an inverter, solar cells
or fuel cells, for example. A common method used is the
installation of a power generator which is interfaced with an
automatic or manual transfer switch that is capable of
simultaneously disconnecting the electric utility (mains) power
supply and connecting the alternate power supply to the facility
loads.
[0004] Manual transfer switches usually require an operator to
first start the power generator, and then actuate a handle in order
to initiate the power transfer. Automatic transfer switches enable
unattended operation where monitoring circuits automatically detect
power disturbances, initiate automatic starting of the generator
system, and proceed to transfer power from one supply to the other
using an electrically operated mechanism. The process is reversed
when power is restored.
[0005] Among the problems typically confronting a user of
electricity wishing to install a back-up power supply is the
installation complexity of a traditional transfer switch.
Installation of either manual or automatic transfer switches
requires extensive modification of the user's electrical wiring
system in the facility. This is an expensive process as it must be
performed by electrical professionals and it is a time consuming
process due to safety concerns and the requirement for compliance
with various safety standards. In many cases, this also involves
separating the critical loads that the user wishes to back-up by
connecting them to a sub-panel, which in turn is connected to the
transfer switch. In this scenario, only those loads connected to
the sub-panel are capable of drawing power from the generator
system, which is inconvenient for many users.
[0006] Accordingly, it is desirable to provide a transfer switch
where power is switched ahead of the facility's service entrance
means to permit the engagement of any load within the facility.
This allows the purchaser to avoid the installation of an
electrical sub-panel and increases the convenience to the user.
Still further, it is desirable to provide a rapid and inexpensive
means to install a transfer switch for engagement with the
electrical system.
SUMMARY OF THE INVENTION
[0007] It is an object of the present invention to obviate or
mitigate at least one of the disadvantages described above. More
specifically, it is an object of the present invention to provide a
power transfer switch for switching power supplies to a building or
structure that requires power. More specifically, it is an object
of the present invention to provide a power transfer switch that is
simple to install and does not require modification of the existing
electrical system of the building.
[0008] In a first aspect, the present invention provides a power
transfer switch assembly modularly attachable to a service
installation meter, for selectively connecting one of a main power
supply and an alternate power supply to a power load. The power
transfer switch includes a first power switch switchable between an
ON state and an OFF state, a second power switch switchable between
an ON state and an OFF state, a mechanical interlock having a
locking actuator mechanically coupled to the first and the second
power switches, a controller for monitoring the main power supply,
and a casing containing the first power switch, the second power
switch, the mechanical interlock and the controller. The first
power switch receives the main power supply for coupling the main
power supply to the power load in the ON state. The second power
switch receives the alternate power supply for coupling the
alternate power supply to the power load in the ON state. The
mechanical interlock physically prevents the first power switch and
the second power switch from assuming simultaneous ON states. The
controller switches the first power switch to the OFF state and the
second power switch to the ON state when a disturbance in the main
power supply is detected, and switches the second power switch to
the OFF state and the first power switch to the ON state when the
main power supply is restored. The casing includes load terminals
and line terminals for connection with a meter socket of the
service installation, and line out and line in feed terminals for
connection with a watt-hour meter of the service installation. The
load terminals are connected to the first and second power
switches, the line terminals are connected to the line out feed
terminals, and the line in feed terminals are connected to the
first power switch. In an alternate embodiment of the present
aspect, the casing receives the main power supply from the line
terminals and the alternate power supply from a cable.
[0009] In further embodiments of the present aspect, the controller
includes a remote communication system for exchanging information
with a remote interface unit. The remote communication system
includes hard wired twisted pair communications cable, a power line
communications modem or a wireless radio frequency modem. The
remote interface unit includes a stand-alone user interface
display, a personal computing device or a personal computer, where
the personal computing device includes a personal digital
assistant.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Embodiments of the present invention will now be described,
by way of example only, with reference to the following drawings,
in which:
[0011] FIG. 1 is a schematic overview of the deployment of the
power transfer switch at a building in accordance with an
embodiment of the present the invention;
[0012] FIG. 2 is a detailed diagram of the service installation of
FIG. 1;
[0013] FIG. 3 is a diagram of the transfer switch of FIG. 2;
[0014] FIG. 4 is a diagram of the inside face of the transfer
switch of FIG. 3;
[0015] FIG. 5 is a circuit diagram of the transfer switch of FIGS.
2 and 3 installed between a meter socket and a watt-hour meter;
[0016] FIG. 6 is an illustration of a pair of modified power
switches according to an embodiment of the present invention;
[0017] FIG. 7 is an illustration of the pair of modified power
switches of FIG. 6 assembled with a mechanical interlock in
accordance with an embodiment of the present invention;
[0018] FIG. 8 is an illustration of a pair of power switches
assembled with an alternate mechanical interlock in accordance with
an embodiment of the present invention; and,
[0019] FIG. 9 is a side view of the assembly shown in FIG. 8.
DETAILED DESCRIPTION OF THE INVENTION
[0020] A modularly attachable transfer switch assembly for
operative connection to two power sources and a power load is
disclosed. The transfer switch can be quickly and easily installed
upon existing service installations, and includes one power switch
for selectively connecting a electrical utility power supply to the
power load of a structure, such as a building for example, and a
second power switch for selectively connecting an emergency power
supply to the power load of the building. The transfer switch
includes a mechanical interlock operatively connected to both the
power switches for physically preventing both the power switches
from assuming simultaneous ON positions, and a controller for
controlling the emergency power supply and the transfer switches.
Upon loss or disturbance in the electrical utility power supply,
the transfer switch will automatically activate the emergency power
supply, disconnect the utility power supply from the building and
connect the emergency power supply to the building. When the
electrical utility power supply returns to normal operating levels,
the transfer switch then automatically disconnects the emergency
power supply and reconnects the utility power supply to the
building. The transfer switch is enclosed within a casing adapted
for connection between a watt-hour meter and a meter socket of
existing service installations for simple installation of the
transfer switch.
[0021] FIG. 1 illustrates a preferred application of the transfer
switch embodiment of the present invention. A structure requiring
power, such as a residential building 10, has a power generator 12
for supplying emergency power to an upgraded service installation
14 through cable 16. The upgraded service installation 14 has a
transfer switch modularly attached between the meter socket and the
watt-hour meter of the upgraded meter installation 14, as will be
shown in more detail in FIG. 2. Main power from the utility is
supplied to the upgraded service installation 14 through main power
cable 18, which includes a power cable routed from overhead.
Alternatively, the main power cable can be routed underground. In
the present example, the transfer switch of the upgraded service
installation 14 receives the emergency power from cable 16. Because
of the modular nature of the transfer switch, its installation upon
existing service installations is simple, quick and minimizes the
possibility of wiring errors. Furthermore, there is no need to
modify the electrical wiring system of the building 10. Details of
the upgraded service installation 14 are shown in FIG. 2. In the
event that main power from an electric utility delivered through
main power cable 18 becomes unavailable or is disturbed, the
transfer switch installed upon the upgraded service installation 14
substitutes the main power from the electric utility with power
from the power generator 12. Preferably, the switch over is
automatically performed to minimize inconvenience to the user.
[0022] FIG. 2 illustrates the upgraded service installation 14 of
FIG. 1 in further detail. Upgraded service installation 14 is
mounted to the wall of the building 10 for receiving main power
through main power cable 18 and emergency power from power
generator 12 through cable 16. Upgraded service installation 14
includes a meter socket 20, transfer switch 22 according to an
embodiment of the present invention, and a watt-hour meter 24. The
transfer switch 22 is small enough to fit within meter socket 20,
and includes a set of contact terminals on the load side, and a
mirrored set of contact terminals on the side for connection to the
watt-hour meter 24, which permits quick push-in connection to the
electrical system. Meter socket 20 is connected to main power cable
18 and an internal power conduit 28. The internal power conduit 28
routes power received by the upgraded service installation 14 to a
distribution panel inside the building 10. One end of transfer
switch 22 is mounted onto meter socket 20 for receiving the main
power supply via meter socket 20, and directly receives the
emergency power from cable 16 through any standard plug and socket
interface 26. For example, standard twist lock or pin sleeve
weatherproof connectors can be used for interface 26. Watt-hour
meter 24 displays the power consumed for meter readings, and is
mounted to the other end of transfer switch 22. A rigid conduit 30
serves to protect the cable 16 as it is routed along the wall of
building 10.
[0023] During normal operation, where building 10 receives main
power from the electric utility, upgraded service installation 14
operates as a standard service installation would. This is because
main power is routed through the transfer switch 22 to the
watt-hour meter 24, and then from the watt-hour meter 24 back
through transfer switch 22 to internal power conduit 28. During
emergency operation where the main power is disturbed or
unavailable, the transfer switch 22 effectively disconnects main
power cable 18 from internal power conduit 28. Transfer switch 22
then connects cable 16 to internal conduit 28. Thus, transfer
switch 22 essentially replaces the direct power connection between
the watt-hour meter 24 and internal power conduit 28 with a pair of
switches that selectively connect and disconnect main power and
emergency power to the internal power conduit 28.
[0024] To install the transfer switch 22 to an existing service
installation, the existing watt-hour meter is first removed from
its meter socket and unplugged from the building to expose the
electrical contacts. The transfer switch 22 is then connected to
the meter socket, and the watt-hour meter is connected to the
transfer switch 22. Finally, the cable from the power generator or
other alternate power supply is connected to the transfer switch
22. Those of skill in the art will understand that the casing of
the transfer switch 22 includes male prong terminals adapted to fit
in female prong terminals in the meter socket. Accordingly, the
casing also includes female prong terminals for receiving the male
prong terminals of the watt-hour meter. Therefore the push-in
connection of the transfer switch 22 to the meter socket 20, and
the push-in connection of the watt-hour meter 24 to the transfer
switch is a simple and quick error-free procedure for retrofitting
existing service installations
[0025] FIG. 3 is a diagram of the transfer switch casing 22 of FIG.
2 showing a layout of the male prong terminals discussed above. The
face of transfer switch 22 shown in FIG. 3 has a pair of line
terminals shown as male prong terminals 40 and 42, for receiving
main power from main power cable 18, a pair of load terminals shown
as male prong terminals 44 and 46, for providing either main power
or emergency power to internal power conduit 28. A fifth neutral
terminal 48 is provided for an alternate embodiment of the present
invention to be discussed later. In this particular embodiment, all
male prong terminals 40, 42, 44 and 46 are identically oriented and
positioned in a square or rectangular pattern. Accordingly, the
pattern of these prong terminals is the same as the pattern for the
terminals of the watt-hour meter 24. The neutral terminal 48 is
rotated 90 degrees relative to the other prong terminals, and
positioned between prong terminals 40 and 44. As previously
mentioned, the hidden face of transfer switch 22 includes female
prong terminals having the same pattern as male prong terminals 40,
42, 44 and 46 in order to receive the watt-hour meter 24. Although
not shown, transfer switch 22 includes a socket for receiving
emergency power from cable 16.
[0026] FIG. 4 is a diagram of the inside face of transfer switch 22
shown in FIG. 3. More specifically, FIG. 4 shows the inside face of
the transfer switch end having male prong terminals. All the male
prong terminals are supported within insulated mounting block 50,
each being connected to a respective conducting terminal 52 except
neutral terminal 48 that is connected to a neutral bus and
conducting terminal 54. When assembled as a transfer switch 22,
conducting terminals 52 and 54 are connected to components within
it. FIG. 4 further illustrates the relative arrangement of the male
prong terminals with respect to each other.
[0027] A detailed description of the transfer switch according to
an embodiment of the present invention now follows with reference
to the system circuit schematic of FIG. 5. The transfer switch of
the present embodiment is a self enclosed system that performs
power detection and power switching functions according to the
status of the main power supply delivered through the main power
cable 18 of FIG. 2. FIG. 5 illustrates the electrical
interconnection between meter socket 20, transfer switch 22, and
watt-hour meter 24 shown in FIG. 2, as well as the circuit diagram
for transfer switch 22 according to an embodiment of the present
invention. Many of the reference numerals in FIG. 5 correspond to
the same numbered reference numerals appearing in FIGS. 2 and
3.
[0028] In FIG. 5, transfer switch 22 is interconnected to meter
socket 20 through terminals 40, 42, 44, 46 and 48 as previously
discussed, and interconnected to watt-hour meter 24 through its
terminals 60, 62, 64 and 66. Terminals 60 and 62 are line out feed
terminals and terminals 64 and 66 are line in feed terminals, both
for connecting with the watt-hour meter 24. Main power provided
through meter socket 20 via terminals 40 and 42 is routed directly
through transfer switch 22 to watt-hour meter 24 through terminals
60 and 62. The main power is then returned to transfer switch 22
through terminals 64 and 66. The alternate power supply is
connected to power generator terminals 68, 70 and 72. Power from
either the main power supply or the alternate power supply is
supplied to the building through the meter socket 20 via terminals
44 and 46. Transfer switch 22 includes a pair of power switches 74
and 76, a controller 78 and a mechanical interlock 80. Power switch
74 receives main power from terminals 64 and 66, and has an output
connected to terminals 44 and 46. Power switch 76 receives
emergency power from terminals 68 and 70, and also has its output
connected to terminals 44 and 46. Controller 78 provides a
switching signal to each power switch, and mechanical interlock 80
physically prevents both power switches 74 and 76 from assuming the
ON state. It should be understood that in the ON state, each power
switch is in a conductive state to couple its input to its output.
Otherwise in the OFF state, each power switch is in a
non-conductive state. The physical interaction between the
mechanical interlock and both power switches according to the
present embodiment is described in more detail later with reference
to FIGS. 6 and 7. Generally, power switches 74 and 76 perform a
multiplexing function in accordance with the switching signals
provided by the controller 78.
[0029] The controller 78 is responsible for a variety of functions
in addition to providing switching signals to the power switches.
According to an embodiment of the present invention, controller 78
senses main power voltage and frequency, power generator voltage
and frequency, provides a start signal to the power generator,
performs all the required start-up actions, re-transfer to normal
delays, and logic functions as well as communications to optional
power control systems of the building. If the power generator has
an engine control unit, the engine control unit will handle
generator operation in response to the start signal received from
controller 78. Although additional connections to and from
controller 78 are not shown in FIG. 5 to simplify the schematic,
those of skill in the art will understand these additional
connections would be present to enable its other functions.
[0030] Each power switch is now described in further detail. Power
switches 74 and 76 are commercially available components, and
generally include a pair of mechanical switching elements and a
solenoid for actuating the mechanical switching elements between
their ON and OFF states. One such power switch is the Series 36,
200 Amp switch from BLP Components Limited for example. Power
switch 74 includes mechanical switching elements 84 and 86 for
selectively coupling terminals 66 and 64 to terminals 44 and 46
respectively. Solenoid 88 receives a switching signal from
controller 78 for actuating mechanical switching elements 84 and 86
via switch actuating line 90. Power switch 76 includes mechanical
switching elements 92 and 94 for selectively coupling terminals 68
and 70 to terminals 44 and 46 respectively. Solenoid 96 receives a
switching signal from controller 78 for actuating mechanical
switching elements 92 and 94 via switch actuating line 98.
Mechanical interlock 80 being a non-electrical component of
transfer switch 22, is physically coupled to both power switches 74
and 76 and shown in FIG. 5 and does not provide or receive any
electrical signals.
[0031] The operation of transfer switch 22 is now described. During
normal operation when the main power supply, typically the electric
utility, is available, switch elements 84, 86 are closed and switch
elements 92, 94 are open. Accordingly power switch 74 is in the ON
state and power switch 76 is in the OFF state, allowing transfer
switch 22 to supply the building with power from the electric
utility. When controller 78 detects a disturbance in the main power
supply, a start signal is sent to the power generator to initiate
emergency power generation. Controller 78 then sends switching
signals to power switches 74 and 76 such that power switch 74 is
switched to the OFF position to open switch elements 84, 86 and
power switch 76 is switched to the ON position to close switch
elements 92, 94. Now the building receives power from the power
generator via terminals 68 and 70. Controller 78 continues to
monitor the main power supply, and proceeds to reverse the state of
each power switch when the main power supply becomes available
again.
[0032] Due to mechanical interlock 80, power switches 74 and 76 are
physically limited to the following three combinations of
states:
[0033] 1) power switch 74 ON, power switch 76 OFF,
[0034] 2) power switch 74 OFF, power switch 76 ON,
[0035] 3) power switch 74 OFF, power switch 76 OFF.
[0036] A fourth possible combination, where both power switches are
ON is physically prevented by mechanical interlock 80. The
simultaneous connection of both the active main power supply and
the active emergency power supply can cause electrical damage to
the building. Furthermore, if the main power supply is inactive,
the connection of the emergency power supply may result in the
power generator transmitting power back through the main power
cables, thereby presenting a possible electrical hazard to electric
utility personnel working on the main power supply.
[0037] In the event that neither the main power supply or the
alternate power supply is available, a battery backup system is
included within transfer switch 22 to ensure that the controller 78
and power switches 74 and 76 are operable. The battery backup
system would include apower supply for charging a battery, where
the power supply can receive power from either the main power
supply or the alternate power supply. Alternatively, the controller
78 and power switches 74 and 76 can receive power from the starting
batteries of a power generator. This can be implemented by
connecting a cable from the starting batteries to the transfer
switch 22.
[0038] FIG. 5 showed the power switches 74, 76 and mechanical
interlock 80 as functional blocks within transfer switch 22. FIGS.
6 and 7 illustrate these components in their physical form to show
their mechanical interactions with each other.
[0039] FIG. 6 is a side view of a pair of power switches, each
representative of the Series 36, 200 Amp switch from BLP Components
Limited. These power switches are suitable for use as power
switches 74 and 76 in FIG. 5. Alternate power switches can be used,
where each power switch is preferably a double pole, single-throw
switch having rare earth magnets to ensure rapid actuation and high
contact pressure between the switch contacts of the switching
elements. Although the power switches are commercially available,
minor modifications have been made to them for enabling lock-out of
the simultaneous ON states of both power switches when mated with a
mechanical interlock. In FIG. 6, the top power switch is
illustrated in the OFF state while the bottom power switch is
illustrated in the ON state. Each power switch 100 includes power
switch terminals 102, 104, 106 and 108 and an actuator pin 110.
Power switch terminals 102 and 106 are connected to each other in
the ON state, as are power switch terminals 104 and 108. Actuator
pin 110 is in sliding engagement with the power switch body, and is
coupled to the internal switch element such that the pin slides in
and out corresponding to the state of the power switch. The power
switch can be switched to the OFF state manually by pushing in
actuator pin 110. Modifications to the power switch include
formation of opening 112 and installation of an interconnection
member 114 on one side of each power switch 100. Opening 112
provides access to the internal switch element for connection of
the interconnection member 114, which slides linearly along the
opening 112 in accordance with the state of the power switch.
Interconnection member 114 can be a cylindrical piece of suitable
material retained on a nipple within the power switch at one end,
with a suitable form at its opposite end for engaging a locking
actuator of a mechanical interlock. In a preferred embodiment, the
interconnection member 114 is a brass tube slotted at one end. The
locking actuator and mechanical interlock are described in further
detail with reference to FIG. 7.
[0040] The modified power switches of FIG. 6 are shown in an
assembled configuration in FIG. 7, in which they are separated by a
mechanical interlock 80, such as the illustrated lock out preventor
having model number G269/1 by Lovato. It is noted that the power
switch terminals are not shown for clarity of the diagram. If the
power switches and mechanical interlock are assembled with the
orientation shown in FIG. 6, then FIG. 7 shows a top view of the
assembled mechanical interlock 80 and the modified power switches
100. Mechanical interlock 80 includes a locking actuator, such as
the pair of L-shaped tabs 120 that are in sliding engagement with
the body of mechanical interlock 80. The L-shaped tabs 120 are
mechanically engaged with each other within the body of mechanical
interlock 80 such that full extension of one L-shaped tab 120
inhibits extension of the other L-shaped tab 120. The end of each
L-shaped tab 120 is connected to an interconnection member 114 such
that movement of the L-shaped arm 120 follows that of the
interconnection member 114 as it switches between the ON and OFF
states. Mechanical interlock 80 prevents both power switches from
being in the ON position at the same time. In other words, it
prevents both actuator tubes 114 from shifting to the right-most
position. In FIG. 7, the top-most power switch is in the ON state
and the L-shaped tab 120 it is connected to is fully extended from
mechanical interlock 80. The bottom-most power switch on the other
hand, is in the OFF state and the L-shaped tab 120 it is connected
to is fully withdrawn. Hence, if a first tab 120 is extended, it is
mechanically impossible to extend the second tab 120. At this time,
the first tab 120 can be withdrawn, setting both power switches in
the OFF state. For the previously mentioned safety reasons, the
internal mechanical system of mechanical interlock 80 prevents both
the first and second tabs to be simultaneously extended to enable
simultaneous ON states of both power switches. However, the
internal mechanical system permits exactly one tab to be extended
and both tabs to be withdrawn. The mechanical interlock 80 is
preferably retained within a block of insulating material which
provides physical separation and thermal and electrical insulation
between the power switches.
[0041] An alternative mechanical interlock system that does not
require modifications to the power switches is shown in FIGS. 8 and
9. FIG. 8 shows a top view of a pair of unmodified power switches
assembled in the same configuration as the assembly of FIG. 7. FIG.
9 shows a side view of the assembly of FIG. 8. The configuration of
the power switches is similar to the configuration shown in FIG. 7,
except that an insulating spacer 130 is sandwiched between the two
power switches. It is noted that the power switch terminals are not
shown for clarity of the diagram. The alternative mechanical
interlock includes a U-shaped bracket 132 having its ends secured
to the bodies of both power switches 100. The locking actuator is a
rocking bar 134 pivotally connected to the walls of the U-shaped
bracket 132 through a central pivot, and the ends of the rocking
bar 134 are in contact with a respective actuator pin 110.
[0042] In operation, rocking bar 134 ensures that both actuator
pins 110 never extended in the ON state at the same time. If a
first actuator pin is already extended in the ON state, the second
actuator pin can push the first actuator pin to the OFF state when
the second actuator pin is switched to the ON state. Additionally,
both actuator pins 110 can simultaneously retract to the OFF
state.
[0043] The previously described transfer switch components,
including power switches, controller and the mechanical interlock,
are preferably contained within a casing which allows modular
attachment of the transfer switch between the meter socket and
watt-hour meter of a service installation at a building.
Furthermore, re-wiring of the building or modification to the
existing electrical system is avoided in order to provide the
capability for automatically coupling either the main power supply
or an emergency power supply to the building.
[0044] In an alternate embodiment of the present invention, the
transfer switch is mated to a permanently installed power
generator, and the wiring connection between the power generator
and the transfer switch is permanent. For example, wires from the
cable can be attached to terminals of the transfer switch casing
via screw down connectors, or other suitable means for attaching
the cable to the transfer switch terminals. Preferably in the
present alternate embodiment, the typical wiring method will be via
a cable in a rigid conduit such as metal or PVC above ground or
underground, depending on the application. An electrical junction
box is preferably mated to the casing of the transfer switch
itself. To avoid running the rigid conduit directly to the
electrical junction box, a length of flexible watertight conduit is
coupled to the rigid conduit. The cable 16 can then be pulled into
the electrical junction box. Lead conductors from the transfer
switch will be provided in the electrical junction box complete
with barrel type mechanical connectors and insulating boots to
allow for quick and easy connection without the need for special
crimping tools.
[0045] It should be understood to those of skill in the art that
the aforementioned embodiments of the present invention can be used
with 50 A generators. In an aspect of the present alternate
embodiment the transfer switch can be used with 200 A generators.
In the present aspect, the electrical junction box is inserted in
line between the cable plug 26 and cable 16 in FIG. 2 due to the
size of the junction box required to allow for 200 A wire
installation. Furthermore, the size of the 200 A wire (2/0 awg Cu)
imposes specific wiring requirements to the neutral conductor 48
shown in FIGS. 3 and 4 due to the limited amount of available space
in meter socket 20 of FIG. 2. For example, a fifth 200 A plugable
terminal can be installed into the existing meter socket 20, where
the plugable terminal consists of a copper or aluminum bus custom
formed to be able to be retrofitted with relative ease into the
meter socket. Then the neutral terminal 48 of the transfer switch
can be plugged into the fifth plugable terminal. Alternatively, a
flexible lead can be installed in the existing meter socket instead
of a plugable terminal. The flexible lead can consist of a custom
fabricated plug to connect to the transfer switch, and connection
to the service neutral would be via a tap connector, such as either
a split bolt connector or insulation displacement connector. The
plug connector would then attach to the transfer switch prior to
installing it into the meter socket via a bus bar extension from
the transfer switch, and held in place with a thumbscrew. Using
extra flexible conductor would allow the installer to complete the
installation by pushing the meter into place. There are many
possible methods to interconnect a 200 A line to the transfer
switch, which would be obvious to those of skill in the art.
[0046] In further alternate embodiments of the described transfer
switch, a mechanical interlock is not required because logic within
the controller can ensure that both power switches are prevented
from attaining simultaneous ON states. Hence any type of power
switch can be used and customization of the power switches to
accommodate a mechanical interlock is unnecessary.
[0047] In another alternative embodiment, the transfer switch
includes remote communications capabilities for exchanging data
between the user via a remote interface unit and the transfer
switch, or the transfer switch and the engine control unit of a
power generator. The remote communication system can be integrated
with the controller of the transfer switch since the controller is
capable of monitoring various operating parameters. The remote
communication system can include a hard wired twisted pair
communications cable to the remote interface unit, a power line
communications modem embedded in the transfer switch controller to
communicate over the existing residential wiring to the remote
interface unit, and a wireless radio frequency modem embedded in
the control unit to communicate with the remote interface unit. The
remote interface unit can include a stand-alone user interface
display, which displays the status of the switch, giving position,
generator status and normal supply status. Alternately, the remote
interface unit can be an interface unit allowing the user via
software to view the status information on a personal computing
device (PC, Laptop, PDA). The communication link would allow
bi-directional communication between the user interface device and
the switch unit allowing the user to adjust settings and perform
system tests. The communication link may also be employed to work
in conjunction with optional power control systems that may be
implemented, such as a load control system for example.
[0048] As those of skill in the art will appreciate, the transfer
switch assembly of the present invention can withstand the entire
load draw of a building while being small enough to fit inside a
meter socket adapter. This permits the transfer switch assembly to
be installed ahead of the service entrance, thereby obviating
certain disadvantages of previous transfer switches.
[0049] The above-described embodiments of the present invention are
intended to be examples only. Alterations, modifications and
variations can be effected to the particular embodiments by those
of skill in the art without departing from the scope of the
invention, which is defined solely by the claims appended
hereto.
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