U.S. patent application number 13/492425 was filed with the patent office on 2012-09-27 for automatic transfer switch.
This patent application is currently assigned to GENERAC POWER SYSTEMS, INC. a Wisconsin Corporation. Invention is credited to Donald B. Espeut, JR..
Application Number | 20120242145 13/492425 |
Document ID | / |
Family ID | 41611034 |
Filed Date | 2012-09-27 |
United States Patent
Application |
20120242145 |
Kind Code |
A1 |
Espeut, JR.; Donald B. |
September 27, 2012 |
AUTOMATIC TRANSFER SWITCH
Abstract
An automatic transfer switch apparatus for use with a standalone
generator, for supplying emergency power to a residence or small
business. The automatic transfer switch apparatus is configured to
sense a utility line failure, start up and stabilize the generator,
and switch over the household circuits from the utility to the
generator, and switch back when the utility recovers. The transfer
switches incorporate motor driven switch interlock mechanisms in
several embodiments as well as various operational features
Inventors: |
Espeut, JR.; Donald B.;
(Lawrenceville, GA) |
Assignee: |
GENERAC POWER SYSTEMS, INC. a
Wisconsin Corporation
Waukesha
WI
|
Family ID: |
41611034 |
Appl. No.: |
13/492425 |
Filed: |
June 8, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12462142 |
Jul 30, 2009 |
8222548 |
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13492425 |
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Current U.S.
Class: |
307/23 |
Current CPC
Class: |
Y02B 70/30 20130101;
H02J 2310/12 20200101; H01H 9/26 20130101; Y04S 20/222 20130101;
H02J 9/08 20130101; H01H 2300/018 20130101; Y02B 70/3225 20130101;
H02J 3/14 20130101; Y04S 20/248 20130101 |
Class at
Publication: |
307/23 |
International
Class: |
H02J 9/00 20060101
H02J009/00 |
Claims
1. In an electrical system normally supplied with electrical power
from a utility source, the electrical system further having an
automatic starting auxiliary electrical power source having a
predetermined maximum capacity, a method for setting up
distribution of auxiliary electrical power amongst a plurality of
loads, comprising the steps of: providing a switching apparatus
disposed between the source of electrical power and at least two
electrical loads wherein at least one of the electrical loads is a
mandatory load and at least one of the electrical loads is a
discretionary load, and configured to be able to bring the source
of electrical power selectively into electrical contact with any
combination of the at least two electrical loads; providing a
controller, connected to the utility source, the auxiliary
electrical power source, and each of the at least two electrical
loads; providing the controller with memory for storing information
regarding the electrical system, starting the auxiliary electrical
power source and monitoring the output of the auxiliary electrical
power source; setting each load on the electrical system to its
maximum demand setting; interrupting electrical contact between the
auxiliary electrical power source and each of the loads; connecting
a first load on the electrical system, to the auxiliary electrical
power source; causing the controller to sense in the electrical
system the first connected and storing that value as an assigned
maximum value of that first connected load in memory; disconnecting
the first connected load from the auxiliary electrical power
source, and successively connecting, sensing, storing and
disconnecting each remaining load in the system to and from the
auxiliary electrical power source, until all discretionary loads in
the system have been connected, and their maximum load values
sensed.
2. The method according to claim 1, further comprising the steps
of: assigning a disqualification value to any load sensed by the
controller that exceeds a predetermined value of the capacity of
the auxiliary electrical power source.
3. A system for distribution of electrical power amongst a
plurality of loads comprising: a source of electrical power, having
a predetermined maximum capacity; at least two electrical loads,
each electrical load having been assigned a predetermined priority
value relative to the provision of electrical power from the source
of electrical power; a switching device disposed between the source
of electrical power and the at least two electrical loads, and
configured to be able to bring the source of electrical power
selectively into electrical contact with any combination of the at
least two electrical loads; a controller, connected to the source
of electrical power and each of the at least two electrical loads;
the controller having memory therein containing as a stored value
the predetermined maximum capacity of the source of electrical
power; the controller having memory therein containing as stored
values the predetermined priority values of the at least two
electrical loads; the controller having memory therein containing
as stored values the respective maximum load values of each of the
at least two electrical loads, when each such electrical load is
active; the controller being configured to cause the switching
device to bring into electrical contact with the source of
electrical power each successive electrical load active and calling
for electrical power, in order of descending priority so long as
the addition of each successive electrical load results in a total
load less than a predetermined percentage of the predetermined
maximum capacity of the source of electrical power, such that if
the addition of a prospective successive lower priority load would
cause the total load to equal or exceed the predetermined
percentage, the prospective successive lower priority load would
not be brought into communication, if at all, with the source of
electrical power, until the total of the total of the loads already
in contact with the source of electrical power and the prospective
successive lower priority load is less than the predetermined
percentage; and the controller further being configured, in the
event that the total of the loads in contact with the source of
electrical power exceeds the predetermined percentage for a
continuous predetermined period of time, to successively disconnect
the loads from the source of electrical power, beginning with the
lowest priority load and continuing in ascending order, until the
resulting total load is less than the predetermined percentage, and
then reconnect, in descending order of priority, the next available
load which results in a total load less than the predetermined
percentage.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional application and claims
priority to U.S. patent application Ser. No. 12/462,142, filed on
Jul. 30, 2009, which claims the benefit of U.S. Patent Application
Ser. No. 61/084,899, filed on Jul. 30, 2008 and U.S. Design patent
application Ser. No. 29/322,214, filed on Jul. 30, 2008.
FIELD OF THE INVENTION
[0002] The present invention relates to the technical field of
transfer switches, for use with portable or stationary electric
generators. In particular, the present invention is directed to an
automatic transfer switch apparatus.
BACKGROUND
[0003] Transfer switches, for use in association with portable or
stand-alone electrical generators, are known in the prior art.
[0004] A private residence, for example, may normally receive its
electrical power from a utility company. For various reasons,
however (location in a region prone to severe weather, etc.), the
homeowner may desire a back-up source of electrical power, so that
comfort or at least habitability of the residence can be
maintained, during periods in which utility power is
unavailable.
[0005] Typically, a gasoline, diesel, propane or natural gas
internal combustion engine-powered electrical generator, capable of
generating split-phase alternating voltage, may be installed in or
near the residence, and arranged to be connected to one or more of
the electrical circuits in the residence in order to provide the
desired back-up power.
[0006] However, one cannot simply leave the back-up generator
permanently connected, in parallel with the utility power, to the
residential electrical circuits, nor can one simply connect and
power up a back-up generator, without first disconnecting the
residential circuits from the power lines coming in from the
utility. The reason for this is the possibility that some of the
current generated by the back-up generator may inadvertently be
backfed into the utility power lines, which may lead to personal
injury and/or damage to utility equipment (transformers, etc.).
[0007] Transfer switches have been provided to establish the
electrical connections between the utility, the residential
circuit(s) and the back-up generator. Prior art residential
transfer switches typically have been manually actuated devices;
known as "break, then make" switches. This means that when the
switch is thrown, the connection between the residential circuit(s)
and whichever current source is at the time actually connected to
the residential circuit, is broken, before the connection is made
between the residential circuit, and the current source which is
being substituted in.
[0008] In a typical situation, utility power fails or falls
drastically. The residence owner proceeds to start up the back-up
generator, and once operating speed and voltage have been attained,
the switch is manually thrown, to disconnect the utility from the
residential circuit, and thereafter, cut in the current from the
back-up generator.
[0009] Prior art manual transfer switches are capable of providing
the simple function of serving to safely accomplish the
substitution of power sources. However, such prior art manual
switches require the presence of the homeowner, in order to
accomplish the transfer. This may be undesirable, in that some
appliances (e.g., refrigerator or freezer, sump pump, etc.) should
not go without power for extended periods of time. If a homeowner
is absent for more than an hour or two, continued power outages may
cause potentially serious damage or injury to equipment, property,
pets, etc.
[0010] Accordingly, it would be desirable to provide a transfer
switch for residential/small business environments and the like,
that is capable of actuating automatically, upon sensing a
sustained interruption of utility-supplied electrical power.
[0011] It would also be desirable to provide an automatic transfer
switch, that is capable of starting a back-up generator, upon
sensing a sustained interruption of utility-supplied electrical
power, and disconnecting the utility and connecting the back-up,
when the back-up generator is capable of assuming the load.
[0012] These and other desirable characteristics of the invention
will become apparent in light of the present specification, claims
and drawings.
SUMMARY OF THE INVENTION
[0013] The invention is directed to automatic transfer switches for
switching the supply of electrical power to a load, between utility
and auxiliary electrical power sources. Several mechanical circuit
breaker switch interlock mechanisms are provided, which are
propelled by motor assemblies that are controlled by programmable
controllers that monitor one or more characteristics of the utility
electrical power source, for initiating a switch to auxiliary
electrical power, when it appears that the utility electrical power
may fail. The interlock mechanisms are break before make
mechanisms, and each includes a motor driving actuator, and an
interlock member passively mounted in cooperation with the handles
of the circuit breaker switches, to ensure that the respective
circuit breaker switches cannot be both in their respective "ON"
positions simultaneously.
[0014] The invention also comprises an automatic transfer switch
construction, in which the circuit breakers, and controller are all
mounted together on the common power buss for the automatic
transfer switch. In embodiments of the invention, in which the
automatic transfer switch is switchably connected to a plurality of
distinct and electrically isolated circuits, the controller is
advantageously configured to have a learning function upon
installation, so as to detect and record in memory the values for
the loads imposed by each of the plurality of circuits, for
facilitating load management. The controller also has a dynamic
load shedding function, which enables the controller to shed
discretionary loads if the total load being powered exceeds a
predetermined percentage of the auxiliary power capacity, but
enables it to go to the discretionary load, that is next in
priority which has a load that, when summed with any mandatory
loads (and higher priority discretionary loads) does not exceed the
predetermined percentage of auxiliary power capacity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a basic schematic of a power supply system for a
residence that is provided with a back-up generator (or other
auxiliary power source), as well as utility power.
[0016] FIG. 2 is a schematic view of an automatic transfer switch
according to an embodiment of the invention.
[0017] FIG. 2A-8 are schematic illustrations of an interlock
mechanism (omitting the motor) for an automatic transfer switch
according to the embodiment of FIG. 2, showing a transfer
procedure.
[0018] FIG. 8A is a representative wiring schematic for an
automatic transfer switch according to the embodiment of FIGS.
2-8.
[0019] FIG. 9 is an illustration of an automatic transfer switch
according to the embodiment of FIGS. 2-8, showing in particular,
the enclosure and the interlock mechanism.
[0020] FIG. 10 is an enlarged view of the motor and actuator
associated with the interlock mechanism for the automatic transfer
switch of the embodiment of FIGS. 2-9.
[0021] FIG. 11 is an illustration of an automatic transfer switch,
according to another embodiment of the invention, shown in its
enclosure, with the dead front panel removed, to reveal the buss,
controller, and motor for driving the interlock mechanism.
[0022] FIG. 11A is an exploded perspective view of the interlock
mechanism according to the embodiment of FIG. 11.
[0023] FIG. 12 is an enlarged view of the interlock mechanism
according to the embodiment of FIG. 11.
[0024] FIGS. 13-18 are schematic illustrations of an interlock
mechanism (omitting the motor) for an automatic transfer switch
according to the embodiment of FIG. 11, showing a transfer
procedure.
[0025] FIG. 19 is an enlarged view of components of the interlock
mechanism according to the embodiment of FIG. 11.
[0026] FIG. 19A is a representative wiring schematic for an
automatic transfer switch according to the embodiment of FIGS.
11-19.
[0027] FIG. 20 is a front view of an automatic transfer switch
according to another embodiment of the invention, with the cover
removed to show the dead front panel, and the interlock
mechanism.
[0028] FIG. 21 is an enlarged view of the automatic transfer switch
of FIG. 20, with the dead front panel removed to disclose the
breakers and motor drive for the interlock mechanism.
[0029] FIG. 21A is an exploded perspective view of the interlock
mechanism according to the embodiment of FIG. 20.
[0030] FIGS. 22-27 are schematic illustrations of an interlock
mechanism (omitting the motor) for an automatic transfer switch
according to the embodiment of FIGS. 20-21, showing a transfer
procedure.
[0031] FIG. 27A is a representative wiring schematic for an
automatic transfer switch according to the embodiment of FIGS.
20-27.
[0032] FIG. 28 is a schematic illustration of a representative
control panel for an automatic transfer switch according to the
present invention, showing the function buttons used during the
self-learning mode used during installation or reprogramming of the
automatic transfer switch.
[0033] FIG. 29 is a schematic illustration of an electrical system
of a structure in which an ATS according to the present invention
is used as the sole load center for the system.
[0034] FIG. 30 is a schematic illustration of an electrical system
in which an ATS according to the present invention is used as a
supplement to an existing load center.
[0035] FIG. 31 is a schematic illustration of an electrical system
in which an ATS according to the present invention, is installed
between an existing load center and power sources, to act as a
service disconnect, and to act as a subpanel to supply, e.g., new
loads installed subsequent to loads serviced by the original load
center.
[0036] FIGS. 32-39 illustrate the schematics for representative
circuits comprising the control module for an ATS according to an
embodiment of the present invention.
[0037] FIG. 40 is a schematic of a representative circuit for a
load shed model according to a preferred embodiment of the
invention.
[0038] FIGS. 41A, 41B illustrate a block diagram for the control
module and user interface for an Automatic Transfer Switch
according to an embodiment of the present invention, showing the
connections to utility power and to an auxiliary electrical
generator.
[0039] FIG. 42 illustrates an alternative embodiment of the
interlock mechanism shown in FIGS. 2-8.
DETAILED DESCRIPTION
[0040] While this invention is susceptible of embodiment in many
different forms, there are shown in the drawings and will herein be
described in detail, several embodiments with the understanding
that the present disclosure should be considered as an
exemplification of the principles of the invention and is not
intended to limit the invention to the embodiments so illustrated.
Further, to the extend that any numerical values or other specifics
of materials, etc., are provided herein, they are to be construed
as exemplifications of the inventions herein, and the inventions
are not to be considered as limited thereto.
[0041] The following description and drawings are illustrative and
are not to be construed as limiting. Numerous specific details are
described to provide a thorough understanding of the disclosure.
However, in certain instances, well-known or conventional details
are not described in order to avoid obscuring the description.
References to one, or an, embodiment in the present disclosure can
be, but not necessarily are, references to the same embodiment;
and, such references mean at least one of the embodiments.
[0042] Reference in this specification to "one embodiment" or "an
embodiment" means that a particular feature, structure, or
characteristic described in connection with the embodiment is
included in at least one embodiment of the disclosure. The
appearances of the phrase "in one embodiment" in various places in
the specification are not necessarily all referring to the same
embodiment, nor are separate or alternative embodiments mutually
exclusive of other embodiments. Moreover, various features are
described which may be exhibited by some embodiments and not by
others. Similarly, various requirements are described which may be
requirements for some embodiments, but not other embodiments.
[0043] The terms used in this specification generally have their
ordinary meanings in the art, within the context of the disclosure,
and in the specific context where each term is used. Certain terms
that are used to describe the disclosure are discussed below, or
elsewhere in the specification, to provide additional guidance to
the practitioner regarding the description of the disclosure. For
convenience, certain terms may be highlighted, for example using
italics and/or quotation marks. The use of highlighting has no
influence on the scope and meaning of a term; the scope and meaning
of a term is the same, in the same context, whether or not it is
highlighted. It will be appreciated that same thing can be said in
more than one way.
[0044] Consequently, alternative language and synonyms may be used
for any one or more of the terms discussed herein, nor is any
special significance to be placed upon whether or not a term is
elaborated or discussed herein. Synonyms for certain terms are
provided. A recital of one or more synonyms does not exclude the
use of other synonyms. The use of examples anywhere in this
specification, including examples of any terms discussed herein, is
illustrative only, and in no way limits the scope and meaning of
the disclosure or of any exemplified term. Likewise, the disclosure
is not limited to various embodiments given in this
specification.
[0045] Unless otherwise defined, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which this disclosure pertains. In the
case of conflict, the present document, including definitions will
control.
[0046] The present invention is directed to automatic transfer
switches, which incorporate motorized interlock constructions for
actuating circuit breakers in various configurations.
[0047] In the present disclosure, reference may be made to
"household" circuitry. This is to be understood to mean the
location, the electrical needs for which are supplied normally by
utility power, and which may be supplied, at least in part, during
emergency situations, by auxiliary power. Accordingly, "household"
may be understood to have an expanded meaning to encompass any
residence, business or governmental facility or other structure
(e.g., a church, etc.) having a use for auxiliary power.
[0048] FIG. 1 is a schematic "single-line" diagram, demonstrating
the general environment of the automatic transfer switch, of the
present invention. While only single lines are shown in FIG. 1a, it
is understood that each line actually represents phase A and phase
B wires. Likewise, it is understood that a typical residence will
have numerous outputs from the bus bar in the breaker box.
[0049] In the absence of a generator (or other auxiliary power
source) and transfer switch, a typical residence 10 receives
utility power 11, in the form of line 12, that connects to a
residential electrical distribution box, typically a breaker box,
in which the incoming line A, B and neutral lines connect to
separate bus bars, and then several lines, representing the several
household circuits, emanate from the bus bar. Typically, each
output from the A and B bus bars has a circuit breaker in it.
[0050] In the simplified set-up of FIG. 1, the utility lines A, B
and neutral enter the breaker box 13 of the residence, and connect
to bus bars 14. From bus bars 14, one or more outputs 15 pass
through respective circuit breakers 16, and onto the various
household circuits. In a household that is provided with a back-up
generator (or other auxiliary power source) 17, as shown in FIG.
1a, output(s) 15 are instead routed to transfer switch 18, that
contains one or more relays 19, switchable between the output(s) 15
and the output(s) 20 (through circuit breaker(s) 21). Output(s) 22
then lead to the load(s) 23 for the residence.
[0051] While in FIG. 1, the service power entry/disconnect and load
centers are separately housed. In more sophisticated systems,
whether incorporating an auxiliary power source or not, the service
entry disconnect and load centers may be integrated into a single
housing.
[0052] In particular, the automatic transfer switches of the
present invention may be used in one of three modes: 1) as the sole
load center for the electrical circuitry of a structure (FIG. 29);
2) as part of a retrofit, to augment the function of an existing
load center in a structure (FIG. 30); or 3) as an "alternative"
means for regulating the supply of electricity to a structure or
group of structures (FIG. 31).
[0053] FIG. 29 illustrates an electrical system 219, in which an
ATS 225 of the present invention is being used as the sole load
center through which electrical power is controlled and distributed
in a residence or other structure. ATS 225 will typically be
configured to serve 24-28 electrical subcircuits. Power will be
normally supplied from utility 221, or in the case of an emergency
(or when so chosen by the operator, such as during a test or
"learning" mode, which will be described in greater detail
elsewhere herein) by auxiliary power source (e.g., generator) 223.
Representative circuits 227 that are set up to be supplied with
emergency power may include the household refrigerator, furnace
blower, televisions or computers, etc. Other, heavier, loads 229 in
the house, such as air conditioning, electric water heater or well
pump, may require inline relays 231.
[0054] ATS 225 of the present invention will be provided with a
programmable control module 233, the functions of which will be
described in greater detail elsewhere herein. In a basic
installation situation, ATS will be configured to supply any
circuit demanding power, during normal times of utility supplied
power. However, because it is usually cost-prohibitive to specify
an auxiliary power source that has the capacity to fully supply
every possible circuit in a system simultaneously, a resident
typically will have to select a specific group of loads which will
be eligible to receive power during emergency operation, so that
the total capacity represented by the emergency loads, does not
exceed the capacity of the auxiliary power source. In the absence
of the "load shedding" feature described hereinafter, ATS 225 will
be configured only to supply auxiliary power to those circuits in
the system, part of a fixed group of circuits, which have been
previously selected as "base" or "mandatory" circuits.
[0055] The auxiliary transfer switches of the present invention can
be optionally provided with the ability to selectively connect or
disconnect various circuits within the system, in accordance with
pre-established priorities determined by the residence owner at the
time of installation. There will always be a certain group of
loads, which may be considered to be mandatory or base loads, which
will be supplied current from the auxiliary or emergency power
source, under all circumstances. Presumably, a consumer will have
the budget to enable them to obtain an auxiliary or emergency power
source which has an available power output which will be capable of
meeting or exceeding the total instantaneous demand presented,
should all of the loads which are designated as mandatory or base
loads present their maximum load demands all at the same time.
Exactly what those mandatory or base loads are to be, is a matter
of personal choice for the consumer, but examples of loads which
may be mandatory or base loads could be include: medical support
devices; basic lighting in crucial areas of a residence; freezer or
refrigerator; water pump; septic system; sump pump; heating (in
cold climates) or air conditioning (in hot climates).
[0056] On the other hand, there may be some loads which may be
deemed optional (nice to have access to during emergency
operations, but not critical), and thus suitable for "load
shedding" operations. These loads may include: AC (in colder
climates), heat (in warmer climates); water heater; garage door;
security devices. Amongst these "load shed" loads, it is possible
for the consumer to designate which of these load shed loads are
more important or more desirable, and to cause the automatic
transfer switch to be able to manage these load shed loads so that
those designated as having higher priority are supplied power (if
available) over lower priority loads.
[0057] This procedure, which is known as "load shedding" enables a
generator pr other auxiliary power source, having a certain maximum
rated power output, to be mated with a group of circuits (both base
loads and optional "load shed" loads), the total aggregate maximum
load of which may actually exceed the maximum output rating of the
auxiliary power source. However, it is highly unlikely that all the
loads of a system will be "on" and at full demand, at the same time
and during a utility power outage (in part, of course, because a
consumer can make the conscious decision to turn off various loads
during power outages, and thus dictate, to some extent, what the
potential maximum load can be).
[0058] Accordingly, it is possible, in accordance with the
principles of the present invention, as long as an auxiliary power
source is provided that has the capacity to meet the needs of any
and all "base" or "mandatory" loads that may require power (AC,
water pump, refrigerator), the number of discretionary loads that
may be supplied during emergency operations can be greatly
increased through the use of load shedding. All automatic transfer
switches of the present invention, will be supplied with control
modules, as described herein; to enable load shedding capability,
one or more programmable load management modules must be added
(typically, "plugged in") to the main control module.
[0059] FIG. 30 illustrates another environment in which automatic
transfer switches in accordance to the present invention may be
employed. System 235 is an electrical system in an existing
structure, in which ATS 237 is used to supplement an existing
original load center 239. Utility power 241 will continue to be
routed first through original load center 239, and load center 239
will continue to directly supply those circuits in system 235 that
are not intended to receive emergency power under any
circumstances. The remaining utility power is then directed to ATS
237 to be distributed to the various subcircuits (not shown) that
are intended to receive power during emergency operations, and ATS
237 acts as the load center for those loads. As with system 219,
ATS 237 will be supplied auxiliary power by auxiliary power source
249. Also as with system 219, some subcircuits 243, such as AC,
well pump, water heater, etc., will require in-line relays 245.
Control module 247 may be supplied with load management modules or
not, according to the desires of the owner.
[0060] FIG. 31 illustrates an alternative arrangement, in which in
system 251, in which ATS 253 serves as the service disconnect for
an entire system, which may include more than one structure. ATS
253 is able to isolate the circuits from both utility power 255 and
auxiliary power source 257, which, in this set up, may be a larger
than usual auxiliary power source. In system 251, ATS 253 is
installed between existing load center 261, and the utility and
auxiliary power sources, and serves as an extension of the existing
power center. As in the other set ups, some of the loads 265
regulated by load center 261, such as AC and the like, may require
inline relays. In this configuration, upon installation of ATS 253,
in-line relays 267 would be connected to control module 259. Loads
to be designated as "load shed" loads may be situated in load
center 261, and connected to load shed modules (not shown)
installed in control module 259 of ATS 253. In addition, ATS 253
serves as a subpanel for loads 263, such as a barn, dock or other
outbuilding, which may have been added to the overall electrical
system, subsequent to the loads served by the original load center
261. One or more of the loads 263 may likewise be selected as "load
shed" loads, and connected to load shed modules installed in ATS
253.
[0061] Each ATS according to each embodiment of the present
invention preferably will have several functional features in
common. For example, through the operation of the control module,
each ATS will continuously monitor the state of the utility power
being supplied. As soon as the monitored utility power enters a
state of sustained power loss (for purposes of the present
disclosure, "sustained power loss" may be defined as a voltage drop
below 190 V or 54 Hz or voltage in excess of 280 V or 66 Hz; these
values are meant to be examples, and other ranges may be selected
as desired) for five consecutive seconds, the control module sends
start and run signals to the auxiliary generator (or if another
type of auxiliary power source is being used, sends a suitable
signal to ready that power source to be capable of delivering
power). Once the auxiliary generator is up to speed, the start
signal is curtailed, and the run signal is maintained.
[0062] The ATS then monitors the auxiliary power source (while
simultaneously monitoring the utility power status), and once
auxiliary power is available, transfers the load (in a
break-before-make mode) to the auxiliary power source. When, during
auxiliary power operations, utility power has been restored to a
reliable state (greater than 204 V or 57 Hz or less than 270 V or
63 Hz, sustained), the ATS is programmed to stand by a further
period of time (e.g., sixty seconds), before transferring the load
(again, in a break before make manner) back to the utility. Once
the hand-off has occurred, the ATS is programmed to allow the
generator to continue running, off-load, to allow the generator to
cool down for a predetermined period of time, e.g., five (5)
minutes, and then terminates the run signal to the generator.
[0063] In addition to actual emergency power supply, an ATS
according to the present invention is also programmed to
spontaneously start up ("exercise") the auxiliary power supply as a
test. For example, the ATS may be programmed to start the generator
at periods of, e.g., 0 (no scheduled exercise), 7, 14 or 28 days,
at a time of day pre-selected to cause minimum disturbance to
occupants and neighbors. The ATS also may monitor the state of the
generator battery, as well as the status of the battery
(rechargeable or otherwise) supplying power to the control module
of the ATS itself, and provide a visual indication (via warning
LED) if replacement/maintenance is required. The ATS may also be
configured to provide for a manual override (for a "commanded"
transfer from utility to generator power, using the appropriate
input buttons 203, 201, on user interface/control module 31.
[0064] FIGS. 2-10 illustrate the components of an automatic
transfer switch ("ATS") according to an embodiment of the
invention. FIG. 2 shows transfer switch 25 in an assembled
configuration, with dead front panel 57 having an opening therein
to expose switch handles 37, 39 (to facilitate manual operation
thereof). ATS 25 includes enclosure 27, into which bus 29 is
mounted. Control module (with user interface) 31 is mounted onto
bus 29, as are breakers 33, 35, having switch handles 37, 39.
Interlock member 41 is mounted to the faces of breakers 33, 35, for
reciprocating sliding movement between switch handles 37, 39, along
an axis which extends perpendicular to the axes about which switch
handles 37, 39 pivot. Breakers 33, 35 are of the type, in which
"ON" and "OFF" are at the extremes of the ranges of motion of their
respective switch handles 37, 39, with a "flip-over" point (that
point at which the springs acting on the switch handle "take over"
and drive the handle to the destination toward which it is being
driven, without the need for the application further external
force) somewhere in between. Some breakers may have their
"flip-over" points at exactly midpoint along the arc of possible
motion of the switch handle, while other breakers have their
flip-over points at locations closer to one end of the range of
motion than the other end of the range of motion.
[0065] Actuator 43 includes freely rotatable rollers 45, which are
configured to bear against the "outside" facing surfaces of switch
handles 37, 39. Screw 51 is mounted for free rotation, but no axial
movement, relative to breakers 33, 35. Motor 49 encircles screw 51.
Actuator 43 is mechanically connected to screw 51, via guide
collars 53 and 55, which encircle screw 51. Guide collars 53, 55
straddle motor 49. Accordingly, when motor 49 is energized, it
bears against screw 51, and is caused to move longitudinally along
screw 51, which, in turn, causes actuator 43 to be moved axially
along screw 51, to bear against switch handles 37, 39. In this
embodiment, rollers 45 are cylindrical, disc-shaped rollers,
mounted on hubs, and having side faces which are parallel to the
axes of rotation of the rollers. In practice, while the rollers are
free to rotate, during a transfer operation, they do not. The side
faces of the rollers make variable contact with the sides of the
breaker switches, in that, at some points during the arc of the
breaker switch handles, the "lower" edges of the side faces of the
rollers are contacting the sides of the breaker switch handles, at
other points, there is flat-to-flat contact between the sides of
the rollers and the sides of the breaker switches, and at other
locations, the "upper" edges of the side faces of the rollers are
contacting the sides of the breaker switch handles. The rollers
have diameters which are selected because of the dimensioning
appropriate to obtain the desired timing of the relative movements
of the interlock components and the breaker switch handles.
However, because the rollers do not, in this embodiment, rotate
significantly as a rule, the portions of the rollers that are
"away" from` the breaker switch handles are essentially not
involved in the interlock operation, and could be replaced, e.g.,
by solid bulk structures (fabricated from any suitable material,
such as metal, polymer, rubber, etc.) having the necessary
dimensions in the direction of the breaker switches, as shown in
the photo drawing of FIG. 42 hereto. The rectangular bulk
structures shown therein will likewise have flat contact faces,
extending normal to the plane of the illustration, to provide the
"camming" contact action previously described, but will have little
or no structure extending on the opposite sides away from the
breaker switch handles.
[0066] As mentioned previously, the length of interlock member 41
is sufficient to prevent both of switch handles 37, 39 to
simultaneously be in their respective "ON" positions. However, the
distance between the edges of rollers 45, 47, taken along an axis
extending between their respective rotational axes is sufficient to
enable both switch handles 37, 39 to be simultaneously in their
respective "OFF" positions.
[0067] Motor 49 is actuated by suitable control signals transmitted
from control unit 31, in response to changes in the quality of the
utility power, which is being sensed continuously at very short
intervals, by control unit 31.
[0068] FIG. 2A in particular is an exploded perspective view of the
breakers 33, 35; interlock mounting bracket 34; actuator 43; spring
44; spring roller 46; and rollers 45, 47. Interlock member 41 is
slidably held by fasteners 48, 50 on post 52 emanating from bracket
34.
[0069] The operation of transfer switch 25 may be described with
respect to the configuration shown in FIGS. 2-8 wherein switch
handle 37 of breaker 33 is in its "OFF" position, and switch handle
39 is in its "ON" position. Switch handle 37 is bearing against an
end of interlock member 41, while there is a gap between interlock
member 41, and switch handle 37 (being in its fully "ON" position).
There is similarly a gap between switch handle 37 and roller
47.
[0070] The positions of the switch handles in FIGS. 2, 3 may
represent a transfer switch either just before switch over from
utility to auxiliary power, or from auxiliary power to utility,
depending upon which breaker is connected to which power source.
For purposes of this disclosure, FIGS. 2-3 will represent a
situation in which breaker 33 is connected to utility power,
breaker 35 is connected to an auxiliary generator (or other
auxiliary power source), and the configuration depicted represents
a status, prior to switchover from utility to generator power.
[0071] Control module (with user interface) 31 is connected, via
suitable sensory contacts, to both the utility power source and the
auxiliary power source, and is operably configured to monitor
various preselected parameters (e.g., RMS voltage, current,
frequency) of the power being supplied (or available) from each
source. Controller 31 will be provided with memory, into which will
be programmed predetermined values for one or more of those
parameters. For example, control module (with user interface) 31
may be programmed to monitor voltage, and should the average
voltage, for a predetermined period of time, drop below a
predetermined stored average value, then the control module (With
user interface) 31 is programmed to initiate transfer to auxiliary
power.
[0072] In a system using a fuel-powered generator, control module
(with user interface) 31 will be programmed for and suitably
connected to, a starter-equipped generator. Once conditions
mandating a transfer to auxiliary power have been detected, control
module (With user interface) 31 will send crank and ignition
signals to the generator, and, once the generator is running and is
delivering power above selected start-up values, the start signal
will be terminated, but the ignition signal will be maintained,
until the generator is no longer needed. As soon as the generator
output has reached a predetermined nominal output level, control
module (With user interface) 31 will cause the actuation of the
transfer switch.
[0073] An appropriate signal will be transmitted to motor 49, to
cause motor 49 to rotate, so as to be moved along screw 51 to the
left, as FIG. 2 is observed, to, in turn, cause actuator 43 to be
moved toward the left. Roller 47 will make contact with, and bear
against switch handle 39, which will begin to pivot to the left,
toward its "ON" position. Before it does so, it will push against
interlock member 41, which, in turn, will bear against switch
handle 37, and begin to move it out of its "ON" position, up toward
its "flip-over" position, on its way to its "OFF" position. As
previously mentioned, transfer switches, to be safe, must be
configured to disconnect the active power source, before the
auxiliary power source can be connected ("break-before-make"), with
a momentary time gap of predetermined duration in between, in which
both breakers are in their respective "OFF" positions. As such,
interlock member 41 is of a length sufficient to ensure that it
will drive switch handle 35 to and past its "flip-over" point, to
its "OFF" position, well before switch handle 37 (being directly
pushed by roller 47) arrives at its "flip-over" point.
[0074] Actuator 43 is mounted in such a way as to accommodate a
breaker construction in which, for example referring to the
arrangement of FIG. 2, breakers 33, 35 are configured such that
their flip-over points are not at the midpoint of their respective
handles arcs of movement, but are instead at positions closer to
their respective "ON" positions. This means that the handle
actually has to be pushed beyond the centerpoint of the arc,
against the force of the spring. As such, rollers 45, 47 must be
able to "pass" the positions of the pivot axes of switch handles
37, 39. To do so, actuator 43 can pivot, slightly relative to screw
51, away from the faces of breakers 33, 35, to enable rollers 45,
47 to "climb up" the inclined faces of switch handles 37, 39, when
they are pushed past the midpoints of their arcs of travel. A
projecting tail end of coil spring 44 serves to push actuator 43,
and, in turn, rollers 45, 47, against the faces of breakers 33, 35,
inasmuch as, depending upon the direction that motor 49 may be
turning at any particular phase of operation of transfer switch 25,
the reactionary torque exerted by screw 51 on motor 49 may tend to
pivot actuator 43 away from the faces of breakers 33, 35.
[0075] Once the transfer has been completed (with switch handles
37, 39 being situated at their opposite ranges of motion, from
those shown in FIG. 2), transfer switch has now connected the
household electrical circuit with auxiliary power. Control module
(with user interface) 31 may be programmed to keep motor 49 and, in
turn, actuator 43, at the position actuator 43 attains, just as
breaker switch handle 39 meets and is propelled past its flip-over
point. Alternatively, motor 49 may be actuated to move back to the
position depicted in FIG. 2, which is a position where breaker 35
is in its "OFF" position, but, if desired, breaker 33 could be
flipped manually to its "OFF" position at the same time.
[0076] A representative wiring schematic for an automatic transfer
switch according to the embodiment of FIGS. 2-8 is provided in FIG.
8A, showing, in particular, the connections 301 for input of power
from utility, connections 303 for input of power from the auxiliary
generator, control connections 305 to the auxiliary generator, and
power connections 307 to the electrical circuits which may be
regulated by load management/load shed modules, as discussed
elsewhere herein.
[0077] Interlock mechanism 105 (shown in exploded perspective view
in FIG. 20A). is mounted on breakers 111, 113, and includes base
plate 119; actuator 129 with arm 139; interlock 121, and rollers
121, 123, 125 and 131.
[0078] The output of the auxiliary power source will be monitored
by control module (With user interface) 31, just as the utility
power source will continue to be monitored, during operation of the
auxiliary power source. Should a voltage be detected from the
utility power inputs that equals or exceeds a stored, predetermined
value, for a minimum predetermined period of time, transfer switch
25 will initiate a transfer back to connection to utility
power.
[0079] To revert to utility power, control module (With user
interface) 31 will cause motor 49 to be actuated so as to move
toward breaker 35. Roller 45 will bear against the adjacent side of
switch handle 33, which will push on interlock member 41, which
will push on switch handle 39. Switch handle 39 will reach its
flip-over point, and arrive at its "OFF" position, before roller 45
can push switch handle 37 into its flip-over point. Again, once
both breakers have been tripped, control module (with user
interface) 31 may either leave motor 49 and actuator 43 at their
positions after flip-over of switch handle 37 has occurred, or it
may be returned to the centralized position of FIG. 2.
[0080] FIGS. 11-19 show an automatic transfer switch 60 according
to an alternative embodiment of the invention. Power buss 64
provides power and/or data to control module (with user interface)
66 for regulating interlock mechanism 76. Breakers 68, 70 (with
corresponding switch handles 72, 74) are mounded side by side,
rather than in tandem, as was the arrangement with respect to the
embodiment of FIG. 2. Because some breakers, which are typically
sold in incremental sizes and power ratings, vary in size, as well
as in the location of the flip-over points for their switch
handles, in order to provide an automatic transfer switch in
accordance with the principles of the present invention in an
economic and space-saving manner (e.g., to accommodate an
off-the-shelf approved metal enclosure), it may be desirable to
arrange the breakers in a side-by-side manner. The interlock
mechanism of FIG. B addresses such breaker configurations.
[0081] Interlock mechanism 76, in accordance with FIG. 11A,
includes breakers 68, 70; base plate 77; interlock member 78;
actuator 86 with arm 94; rollers 80, 90, 88, 82; and drive rod
98.
[0082] Base plate 77 is mounted to breakers 68, 70, or to buss 64,
or even directly to enclosure 62, if so desired. Apertures are
provided in base plate 77, through which switch handles 72, 74
project, and are free to pivot throughout their respective arcs of
motion (which may, in some embodiments, be different for each
breaker). Interlock member 78 is mounted for pivoting movement
around axis 84, to base plate 77, and is provided with freely
rotating rollers 80, 82. Actuator 86 is likewise mounted for
pivoting movement, around axis 92, to base plate 77, and is
provided with freely rotating rollers 88, 90. Actuator 86 further
includes arm 94 and pusher 96. Arm 94 is connected, via drive rod
98, to motor assembly 100, which, as in the embodiment of FIG. 2,
is configured for reciprocating movement along screw 102, depending
upon which direction motor assembly 100 is being directed to run.
Breakers 68, 70 are mounted side-by-side, in the embodiment
illustrated, happen to have switch handles having different
"throws". Accordingly, interlock mechanism 76 is advantageously
configured to address this configuration.
[0083] FIG. 12 is an enlarged view of interlock mechanism 76. In
the embodiment of FIGS. 11 and 12, the "OFF" positions of switch
handles 72, 74 are to the left, as those Figures are viewed, and
the "ON" positions are to the right. Although other arrangements
may be used, for purposes of the present disclosure, breaker 68
will be deemed to be connected between the auxiliary power source
(not shown) and the household power circuit, while breaker 70 will
be considered to be connected between utility power and the
household power circuit. Accordingly, as shown in FIGS. 11-12,
transfer switch 60 is set up so that switch handle 74 of breaker 70
is in its "ON" position, and switch handle 72 of breaker 68 is in
its "OFF" position. Thus, the configuration of FIGS. 11-12
corresponds to a situation in which utility power is being sent to
the household circuit, and (auxiliary power) breaker 68 is off.
[0084] Therefore, in operation, to switch from utility power to
auxiliary power, control module (with user interface) 66 monitors
utility power characteristics. If the requisite power supply
behavior is detected, control module (with user interface) 66 first
prepares the auxiliary power source (not shown), for operation by
sending crank and ignition signals to the auxiliary power source
(if it is a starter-equipped fuel-powered generator). Once the
generator has attained the necessary minimum output parameters, the
crank signal is halted. Control module (With user interface) 66
then transmits a signal to motor assembly 100, causing it to propel
itself along screw 102, away from interlock assembly 76. Drive rod
98 moves upwardly (as FIGS. Band Care viewed), pulling arm 94, and
causing actuator 86 to pivot counterclockwise, around pivot point
92. Before pusher 96 engages roller 82, roller 90 is advantageously
positioned so as to begin to push (to the right) against (auxiliary
power breaker) switch handle 72. Before switch handle 72 reaches
its flip-over point, switch handle 72 contacts roller 80. Interlock
mechanism 76 is configured so that at approximately the same time,
pusher 96 engages roller 82 which, in turn, pushes on (utility
power breaker) switch handle 74. The distance between pivot axis 84
and roller 82 being greater than that between pivot axis 84 and
roller 80, roller 82 pushes switch handle 74 to (and through) its
flip-over point (to break the connection between utility power and
the household circuit) before roller 90 can push switch handle 72
to its flip-over point (to engage the auxiliary power source to the
household circuit).
[0085] In the reverse process, motor assembly 100 moves toward
interlock assembly 76, so as to cause drive rod 98 to push actuator
86 in a clockwise direction. Roller 88 pushes against utility
breaker switch handle 74, which in turn pushes against roller 82,
causing interlock member 78 to pivot. Roller 80 pushes auxiliary
power breaker switch handle 72 out of its "ON" position, and
through its flip-over point, before roller 88 can push utility
breaker switch handle 74 to and through its flip-over point to its
"ON" position.
[0086] As with the embodiment of FIG. 2, interlock mechanism 76, in
an embodiment of the invention, is configured so that there is a
neutral position for actuator 86 such that interlock member 78
permits both breaker switch handles 72, 74, to be in their
respective "OFF" positions simultaneously, but not permit both
handles 72, 74 to simultaneously in their respective "ON"
positions. Likewise, control module (With user interface) 66 may be
configured to cause the interlock mechanism to be returned to the
neutral position after each switching operation, or to cause the
interlock mechanism to simply remain at whichever position it
occupies, immediately after a completed switching operation, as may
be desired.
[0087] A representative wiring schematic for an automatic transfer
switch according to the embodiment of FIGS. 11-19 is provided in
FIG. 19A, showing, in particular, the connections 401 for input of
power from utility, connections 403 for input of power from the
auxiliary generator, control connections 405 to the auxiliary
generator, and power connections 407 to the electrical circuits
which may be regulated by load management/load shed modules, as
discussed elsewhere herein.
[0088] FIGS. 20-27 illustrate another automatic transfer switch
according to an another embodiment of the invention, which is also
directed to a construction incorporating side-by-side breaker
switches 111, 113. In the embodiment of FIGS. 20 27, the breakers
are symmetrical, but provided with long throws, in which the
flip-over points, for going from "ON" to "OFF", and from "OFF" to
"ON" are not at the same location, but rather are at points far
past the midpoint of the arc, in each direction that the switch
handles 115, 117 are being pushed. For example, FIG. 22 illustrates
interlock mechanism 105, with actuator 139 in its neutral position.
Switch handle 115 of auxiliary power breaker 111 is in its "OFF"
position. In order for it to reach its flip-over point, to be
"self" propelled into its "ON" position, breaker switch handle 115
has to be pushed far past the midpoint of the arc of its possible
movement. Conversely, switch handle 117 of utility breaker 113 is
in its "ON" position. In order for it to reach its flip-over point,
to be "self" propelled the rest of the way into its "OFF" position,
breaker switch handle 117 has to be pushed far past the midpoint of
its arc of possible movement, toward its "OFF" position.
[0089] FIGS. 22-27 illustrate the process for switching over from
utility power to auxiliary power. As in the other embodiments,
control module (with user interface) 109 monitors the condition of
the utility power supply, and if the condition(s) warranting
changeover to auxiliary power are met, control module (with user
interface) initiates a switchover by first preparing the auxiliary
power supply, as described herein with the preceding embodiments.
Once the auxiliary power supply is ready, control module (with user
interface) 109 actuates motor assembly 143, to cause drive rod 141
to be moved upwardly (FIG. 21; to the right, in the view of FIGS.
22-27). Actuator 129 is moved counterclockwise, causing roller 131
to push against switch handle 115, which, in turn, bears against
roller 123, which is mounted on interlock member 121. Interlock
member 121 is mounted for pivoting movement around pivot 127, but
is also provided with elongated slot 122, so that interlock member
121 may shuttle from side-to-side, as described in further detail
hereinafter.
[0090] As the switchover process continues, and interlock member
121 pivots, roller 125 bears against switch handle 117 of utility
breaker 113, through to its flip-over point (FIGS. 23-24). Actuator
129 continues to move counterclockwise, causing switch handle 115
to push roller 123 to bear against edge 138 of guide plate 137.
Actuator 129 continues to pivot, and roller 123 moves up and to the
right along edge 138 (as shown in FIGS. 25-27), which movement is
enabled by the presence of slot 122. Eventually, the flip-over
point for switch handle 115 is reached (FIGS. 26-27), and auxiliary
power is engaged. Control module (with user interface) 109 is
suitably programmed at this point, in an embodiment of the
invention, to move actuator 129 back to its neutral position (FIG.
27). As in the other embodiments, the interaction of the actuator,
switch handles, interlock member and, in this embodiment, the slot
and guide member, cooperate to ensure that the breaker which is
engaged, is disengaged prior to the engagement of the breaker being
switched to ("break before make"). As interlock assembly 105 is
symmetrical, the procedure for switching back to utility power from
auxiliary power is the mirror image of the steps and movements
illustrated in FIGS. 22-27.
[0091] A representative wiring schematic for an automatic transfer
switch according to the embodiment of FIGS. 21-27 is provided in
FIG. 27A, showing, in particular, the connections 501 for input of
power from utility, connections 503 for input of power from the
auxiliary generator, control connections 505 to the auxiliary
generator, and power connections 507 to the electrical circuits
which may be regulated by load management/load shed modules, as
discussed elsewhere herein.
[0092] An additional advantageous feature of the automatic system
of the present is the ability to automatically shed loads when the
capacity of the auxiliary generator is insufficient to handle all
of the loads in a given installation. For example, a typical
household may have many high current loads such as air
conditioning, water heater, or electric range, among others. For
reasons of generator cost and fuel consumption, most installations
have auxiliary generators that do not produce enough output power
to run all of these loads simultaneously.
[0093] In the event of a utility power failure resulting in a
switchover to auxiliary generator power some means of disconnecting
these loads has to be provided in order to prevent overloading the
generator.
[0094] The automatic transfer switch of the present invention is
configured to automatically shed up to six different loads. Each
load shed circuit provides a form `C` relay contact that can be
wired in series with the coil of a high current contactor. The
contacts of high current contactors are typically used to turn `on`
and `off` loads like air conditioners, spas, water heaters, ranges,
etc. By wiring the high current contactor coil through the load
shed relay contact allows the load shed relay to have control of
these high current loads. As mentioned above, each load shed
circuit provides a form `C` relay contact, namely, a N.O. (normally
open) and a N.C. (normally closed) contact. At installation, the
installer will use either the N.C. or N.O. contact depending on the
type of circuit needed. As an example, the N.C. contact will be
used in air conditioning circuits and the N.O. contact will be used
in water heater circuits.
[0095] An ATS according to the present invention will be provided
with a programmable (or preprogrammed) control module that is used
to control all of the functions of the ATS. FIG. 28 is a schematic
illustration of a representative control panel for an automatic
transfer switch according to the present invention, showing the
function buttons used during the self-learning mode used during
installation or reprogramming of the automatic transfer switch. The
control module may be provided with a microprocessor and various
software routines, using known components and programming
techniques, to provide the control functions as discussed
hereinbelow. The circuit for the load shed relay is contained on a
smaller printed circuit board ("PCB") that is plugged into the main
PCB of the control Module. In the interest of packaging and cost,
there are may be independent circuits to each load shed module.
[0096] The user interface (part of control module 31) typically may
be provided with several main function buttons, e.g., "TRANSFER"
201; "GENERATOR START/STOP" 203; "EXERCISE" 205; "RESET" 209. In
addition, typically, there will be five indicator lights (typically
LEDs), designed in FIG. 28 by reference numerals 211, 213, 215, 217
and 218. Through these input buttons and the LEDs, an operator may
obtain various information and perform various set-up functions as
described herein. For example, if utility power is available,
indicator 2 (ref. 213) will be continuously lit; if utility power
is powering the load, indicator 1 (ref 211) will be continuously
lit. Alternatively, if generator power is available, indicator 4
(ref 217) will be continuously lit, and if generator power is
powering the load, indicator 5 (ref. 218) will be continuously lit.
The control module may further be programmed, using conventional
programming techniques, to provide additional information about the
operation of the generator, the process of transfer from one power
source to another, the condition of the transfer switch drive
motor, the generator starter, generator battery monitoring, and the
like, depending on which of the indicators is lit and how (whether
continuously or flashing, and if flashing, whether slow or
fast).
[0097] As mentioned previously, rotary dial 202 is used to select
the appropriate rating which matches the auxiliary power source
(generator, typically) that is connected to the electrical system.
In addition, rotary dial 204 is used to select the interval for
exercising the generator in non-emergency conditions (e.g., 0, 7,
14 or 28 days). In an embodiment of the invention, for reasons of
manufacturability, the control module 31 may be configured to
operate with several different embodiments of the ATS of the
present invention; hence, several separate selector scales may be
provided for selecting the interval, with each scale being unique
to a particular ATS embodiment.
[0098] Physically, the user interface is the front face panel of
control module 31, wherein the control circuitry comprises a main
printed circuit board with a microprocessor, containing a
combination of programmable and preprogrammed software. The load
shed modules described herein comprise plug-in modules that are
fitted to appropriate sites on the main printed circuit board. Each
load shed module, which is configured to serve to control two (2)
electrical circuits in the system that have been designated as
"load shed" circuits, functionally is connected to the control
circuits for the relays or breakers that, in turn, control the flow
of current to the particular circuits, systems or appliances which
each particular load shed module serves. For example, a module,
designated for purposes of discussion as Load Shed Module 1 (LSM1)
may have, as one of its assigned circuits, the air conditioning
system of the structure. Depending upon the age of the air
conditioning system, it may be more expeditious to connect LSM1 not
to the thermostat or other consumer-accessible control of the AC,
but rather to connect LSM1 to the power supply for the compressor
unit. In that way, when the ATS control module, in performing its
functions, "decides" that the AC may receive power, the control
module, via LSM1, will either instruct the relay powering the
compressor to close (if it is normally open), or instruct the relay
to open (if it is a normally open relay), without regard to whether
the thermostat theoretically controlling AC operation is calling
for the AC compressor to run. Each load shed module is thus
connected to its respective designated circuits both to "sense"
whether those circuits are demanding power, and to the control
relays or breakers (which are powered relays or breakers) which
govern the supply of power to those designated circuits. The
several load shed loads will be connected to the (in the present
disclosure) up to three load shed modules in descending order of
priority (e.g., LSM1 will get the two highest priority sheddable
loads, LSM2 will get the next two and LSM3 will get the last
two).
[0099] While in the embodiment described herein, six separate
circuits may be accommodated for load shedding operation, in
alternative embodiments of the invention, greater or fewer numbers
of circuits may be regulated through load shedding. Referring to
the present disclosure, six load shed circuits (using 3 load
management modules) are setup on a priority basis, denominated
Priority 1 through 6 in descending order. At the time of
installation of the ATS, an installer would preferably set the
priority of the loads in order of importance to the customer,
without reference to the load status of the system, at the time of
installation. For example, if air conditioning is most important to
that customer then it should have priority one status.
[0100] Functions
[0101] In order for the load shed functions to work properly, a
number of processes have to take place ahead of its actual
function, for example:
[0102] Loan Shed Learning
[0103] The ATS needs to have stored in its memory what current
drain value each high current load imposes on the system, the power
capacity of the generator and the priority of each load.
[0104] This information is acquired (supplied to the ATS control
module) during a process called `Load Shed Learning`, and this
process is preferably executed at the time of installation or when
a new load is installed on the system.
[0105] The prerequisites for load shed learning are as follows:
[0106] All branch circuit breakers in the transfer switch must be
turned to their respective "off" positions, to ensure the accuracy
of current measurements recorded during the "learning" procedure.
[0107] 1. One branch circuit is provided for installer service
lighting to be located physically near the ATS installation site,
to be provided power during the installation and learning
procedure. This nominal load will actually be measured during the
Load Shed Learning test. [0108] 2. To ensure that all loads under
test will come on when their respective circuit breakers are
activated, the installer should set the controls for each load to
their respective maximum settings. In other words, the controls for
these load shed loads should be set for them to draw full load,
e.g., air conditioners should be set for maximum cooling, electric
water heater to maximum heating, and so on. [0109] 3. The ATS
control panel preferably will have a rotary switch or switches
(e.g., switch(es) 202 in FIG. 28) that is designated `Generator
Size`, which must be set for the correct generator capacity. This
switch may have restricted access, e.g., through a hole in the top
of the control module, and the rotary switch may be configured to
be divided into any suitable increments, depending upon the
intended size range of the particular ATS.
[0110] The following steps, and button actuations (referencing the
user interface of FIG. 28) represent an exemplary preferred
embodiment of the invention, and the steps may be modified (e.g.,
by changing selection of the particular "button" or sequence of
buttons to be actuated to represent a particular programming
instruction) without departing from the scope of the invention.
[0111] The `Load Shed Learning` mode may entered, e.g., by first
holding down Service button 206 then pressing Reset button 209
(FIG. 28). This will initiate a pseudo generator transfer cycle
with the following sequence to be followed. All Load Shed circuits
will be caused to open or close their respective relays or breakers
(depending on whether they are normally closed or normally open) so
that the initial state is one in which none of the Load Shed
circuits are receiving any power. In addition, in order to ensure
that reliable power consumption readings for the Load Shed circuits
are obtained, all circuits in the overall system that are
designated as "base" or "mandatory" circuits must be turned off or
disconnected. [0112] 1. The generator starts, runs up to speed--the
control module measures the steady-state output voltage and
frequency of the generator. Once the control module will then
determine whether a valid stable output is attained by the
generator. In systems in which another type of alternative
auxiliary power source is provided (e.g., solar power, stored
battery power, etc.,), that power source is brought to a "ready"
state in which it can supply reliable power if called upon to do
so. Once a valid power signal (or valid "read" state) has been
found by the control module, the control module will initiate
operation of the transfer mechanism, to switch from utility power
to the auxiliary power source. [0113] 2. The control module will
interrogate the load shed circuitry to see how many Load Shed (aka
"Load Management`) Modules are installed on the control module PCB
and in what positions they are located on the PCB. This information
will be placed in memory and used during the Load Shed Learning
Cycle. [0114] 3. The Control Module then looks for a current <2
amps on the generator output (as mentioned, all branch circuit
breakers at this time should be in their respective "OFF"
positions, except for the branch circuit for the installer service
lighting). This latter value will be stored in temporary memory
storage as `service current`. Zero amps would also be considered
valid in the case where no service current is used. [0115] 4. If
`service current` is present and at least one load management
module is installed on the PCB, the control module is preferably
set up to flash all LEDS simultaneously for a predetermined period
(e.g., 10 seconds), serving as an indicator to the installer that,
absent immediate action by the installer, the control module will
proceed immediately into "Automatic" Load Shed Learning Mode.
[0116] 5. The control module will then cause LSM1 to enable power
to be supplied to its first (of two available) assigned circuits,
simultaneously illuminating LED #1 (ref. 211) if desired. The
control circuitry is programmed to "watch" the draw by the first
Load Shed circuit for a predetermined time, e.g., 5 seconds, to see
if the draw exceeds the permissible draw for any single Load Shed
circuit, namely a preselected percentage (e.g., 85%) of the total
available auxiliary power source output. [0117] 6. If the operation
of the first Load Shed circuit passes through the initial five
second period without incident, and the sensed current is above the
nominal "service current" value, then the control module circuitry
will monitor the operation of that circuit for a further extended
period of time, e.g., 20 seconds, during which the peak power draw
will be noted. At the end of that 20 second time period, whatever
the instantaneous maximum current draw was observed, that value is
stored in memory as been associated with the first Load Shed
circuit. The display for LED #1 (ref 211) may shift from a flashing
display to a continuous display, as a visual indication to the
observing installer. Once the peak current draw value has been
stored in memory, then the control circuitry causes LSM1 to cut of
power to the circuit being tested, and turns off LED #1 (211).
[0118] 7. The control module then causes power to be supplied to
the other of the two circuits controlled by LSM #1, and follows the
foregoing steps for that circuit, in addition causing LED #2 to be
illuminated, in turns, in either flashing or steady illumination.
[0119] 8. Each designated "Load Shed" load is measured in turn
following the same sequence. As mentioned, in a preferred
embodiment of the invention, each load management module may
address 2 loads, and in the present invention, up to 3 load
management modules are contemplated (though a greater number of
load management modules may be incorporated into the design without
departing from the scope of the invention). The test will be
terminated once all of the available loads in the load management
modules have been queried and recorded. Some loads, such as AC, may
actually require the use of two circuit breakers, and accordingly,
such a single load may actually occupy both circuits of a single
load service module. [0120] 9. Because (in the illustrated
embodiment) there are only 5 LEDS, load shed load 6 will use LED #1
and #5 together (refs. 211 and 217) as indicators. [0121] 10. If,
during the test of any one of the Load Shed circuits, only the
"service current" load is sensed (during the 20 second "measuring
period), then the control module programming will identify that
circuit as having a potential trouble issue, and will cause the LED
display to be illuminated in a manner that has been pre-established
to signify than a potential trouble item has been encountered. The
current value will be stored. [0122] 11. If, on the other hand, the
control module encounters, during the initial five-second period, a
current draw which is in excess of the allowed current draw (e.g.,
>85% of rated auxiliary power source), then the actual value is
not stored in memory. Instead, a value of "zero" (0) is stored in
memory, which identifies that circuit to the control module
programming as being a disqualified circuit which, during emergency
power operations, is never to be supplied with current. During load
shed learning, if this load is presented to the generator it will
start going into overload. The control module at that time will see
a marked drop in voltage and frequency. The circuit is immediately
shut off, without going through the 20 second "measuring period". A
rapid flashing of the corresponding LED may be caused, to indicate
to the installer that a disqualifying load has been encountered
during the test. If a larger generator or a smaller load is
subsequently installed, a new load shed learning cycle may change
this disqualification. [0123] 12. In the event that fewer than six
loads are to be queued for load shed learning, the load shed
learning cycle can be terminated by pressing the service switch
after the last load has been learned. [0124] 13. If an event occurs
such as described in step 10, in which a trouble load is reported,
then the installer or consumer must inspect whatever devices or
appliances are involved for that circuit to determine the problem
(e.g., burned out bulb or motor). Once the problem has been
addressed, then the learning step for that circuit must be
repeated. In accordance with the present invention, instead of
having to run through the entire automatic cycle, a manual learning
step may be ordered. The installer begins at step 1, and proceeds
through to step 4 (the "all-LEDS flashing" period of ten seconds).
Before the end of that ten-second period, the installer (or
consumer) presses e.g., the "START/STOP" button, to go into manual
mode. [0125] 14. The installer then presses "TRANSFER" until the
LED corresponding to the circuit which had previously reported
trouble is illuminated. The installer then presses "EXERCISE" and
manually actuates the relay associated with that circuit to turn on
the load. The control module then monitors the load for the initial
five-second period, and if valid and above the service current
threshold, and the value is stored. The installer/consumer then
presses "RESET" to exit manual mode. [0126] 15. The control module
may also, if desired, be provided with suitable programming (using
known programming techniques) to permit so-called "quick and dirty"
load shed learning. An installer, using a manual current sensing
device (an "amp clamp"), may personally and individually take
current draw readings for each of the load shed circuits and then,
using a preselected set of button strokes on the user interface,
can input the numerical values for the respective circuits, using a
modified binary code.
[0127] The Load Shed Function
[0128] The load shed function applies only to those non-base,
non-mandatory loads, which are potentially and optionally eligible
to receive power during emergency operations, that are connected to
and managed by load management modules. There may be certain loads
in a system, which are mandatory. Examples of "mandatory loads" may
include (depending upon the preferences of the consumer):
refrigerators and freezers; aquariums; central heating systems;
furnace fans/air handlers; sump pumps; septic lift pumps; pool and
spa anti-freeze pumps; medical, safety and security equipment;
garage door openers; access gates; selected lighting systems; and
computers, printers, fax machines, land-line phones and wireless
routers. These loads, if deemed to be necessary during emergency
power situations (and presuming adequate auxiliary power capacity)
will be permanently connected to the output of the transfer switch,
and, assuming that their total draws do not exceed the capacity of
the auxiliary power source, will receive power during emergency
operations, so long as the auxiliary power source is capable of
meeting their demands. Such mandatory loads, for purposes of this
invention, will be defined collectively as the "Base Load". Any
additional loads (the "load shed" loads) will be met, as a function
of the availability of excess power permits. Such discretionary
"emergency power" loads may include items such as: cooking
equipment; water heating equipment for human consumption; clothes
cleaning equipment; spa, exercise and entertainment equipment (some
of the latter might be included in the "mandatory" list). While the
foregoing categorizations are recommended, of course the ultimate
decision as to what load goes into the mandatory category and what
load goes into the discretionary "load shed" category, and what
load is determined to be entirely unpowered during emergency power
operations, lies with the home owner or installer.
[0129] In the event of a power failure, the loss of voltage on the
main utility circuit breaker will be sensed by the control module.
A timing sequence will be initiated to see if the auto-restart of
the power grid will successfully restore the power. If this is
unsuccessful a transfer sequence will be initiated by the Control
Module. Again, any numerical values provided hereinbelow are by way
of example, and other systems may employ other preselected
numerical values for specific parameters without departing from the
scope of the present invention. [0130] 1. A signal to start the
generator is initiated by energizing the crank and run relays.
[0131] 2. After the generator starts the control module will start
reading the presence of voltage and frequency. [0132] 3. If the
generator voltage and frequency is acceptable, power transfer to
the generator is initiated whereby the motor propelling the
interlock actuator will start driving the actuator mechanism to
turn off the utility circuit breaker followed by turning on the
generator circuit breaker. [0133] 4. During the power transfer to
the generator cycle, the control module will also energize (move to
"OFF") all of the load shed relays installed on the system. This
will ensure that only the non-load shed loads (the "base loads")
will be powered by the generator at this time. [0134] 5. The
control module will initiate a 5 minute delay cycle before trying
to activate any load shed loads. This is to allow residual head
pressure in air conditioner compressors to bleed off before trying
to start the unit, to lower the torque requirements for resumption
of operation under emergency power. [0135] 6. Based on the value
set in the generator size switch, the control module will calculate
the load current relative to the generator size. [0136] 7. From the
pre-stored values gathered during the Load Shed Learning cycle, the
control module will look at all of the stored values of Load Shed
loads weighted by priority. [0137] 8. If the value of the Priority
1 load plus the load already present on the system does not exceed
e.g., 85% of the generator capacity, the Priority 1 load shed relay
will de-energize (move to "ON") enabling the load to function.
[0138] 9. The system will continue to sequence through the stored
Load Shed values on a priority basis continually tallying these
values against the load already present on the generator. [0139]
10. In a preferred embodiment of the invention, the system is
always trying to apply the load shed loads to the system that, in
total, will not exceed 85% of the generator capacity. [0140] 11.
Formula: Base Load(s)+(Load Shed Load 1+Load Shed Load
2+etc)=<85% Generator capacity [0141] 12. Due to the fact that
most Load Shed loads are not constant (e.g., an air conditioner,
heat pump, water heater, etc.), the control module will allow
additional loads to function during the low power periods of these
loads. For example, if the Priority 1 load+the base load does not
allow for any additional loads when the Priority 1 load is at full
power the system will continuously monitor the total load on the
generator for any change in the total load current. When the value
of the total load drops to a value whereby additional loads will
not cause the total load to exceed 85%, the system will bring these
loads on line on a priority basis. [0142] 13. It is possible for
lower priority loads to function if the higher priority loads+the
base load exceed 85% capacity, as the control module and load
management modules may not allow the combination of base load and
higher priority loads, but will allow a combination of base load
and lower priority (and possible lower numerical value) loads to go
online. [0143] 14. If the unlikely event that at any time during
auxiliary power operation, a situation arises in which the total
demand from the base load alone exceeds the aforementioned
preselected percentage (e.g., 85%) of generator power, and/or the
combination of base load demand and any potential load shed load
exceeds the preselected percentage, then load shed operation is not
possible, the ATS may be programmed, as a default operation to
prevent overload and damage to the auxiliary power source, to
transfer back to connection to utility power. The control module
may be suitably programmed to thereafter periodically check the
total demands requested by base and load shed loads and if load
shed operations become possible, a transfer back to auxiliary power
operations may be provided for. [0144] 15. Once utility power is
restored, and all re-transfer parameters are met, the control
module will cause the motor driving the interlock actuator to run
in the opposite direction, causing the generator breaker to
disengage, followed by the engaging of the utility breaker. [0145]
16. The generator enters a 5 minute cool down cycle and all the
installed load shed relays will de-energize allowing all the Load
Shed loads to function on utility power.
[0146] FIGS. 32-39 illustrate the schematics for representative
circuits comprising the control module for an ATS according to an
embodiment of the present invention. In particular, FIG. 32 shows
the microprocessor and clock circuits which control the functions
of the module. FIG. 33 shows the display LED drive circuits and
JTAG programming port used for inputting software into the
microprocessor. FIG. 34 shows representative voltage regulation
circuitry and 12v outputs for generator start crank signals (crank
and run control). FIG. 35 is a schematic for the load shed control
outputs. The load shed modules (see, e.g., FIG. 40) plug into the
control module circuit here. FIG. 36 shows the voltage and
frequency monitoring circuits for the utility and generator power
sources. FIG. 37 is the current monitoring circuit for the
auxiliary generator power output. FIG. 38 is the drive circuit for
the motor (e.g., a stepper motor) for driving the transfer
interlock mechanism for flipping the breakers in the transfer
switch function. FIG. 39 is a schematic for multiplexor circuits
used to control signals to and from the microprocessor of FIG.
32-the user interface switches, load shed presence, generator size,
ATS model information, etc. FIG. 40 is a schematic of a
representative circuit for a load shed model according to a
preferred embodiment of the invention. FIGS. 41A, 41B illustrate a
block diagram for the control module and user interface for an
Automatic Transfer Switch according to an embodiment of the present
invention, showing the connections to utility power and to an
auxiliary electrical generator.
[0147] The foregoing description and drawings merely explain and
illustrate the invention, and the invention is not so limited as
those skilled in the art who have the disclosure before them will
be able to make modifications and variations therein without
departing from the scope of the invention.
* * * * *