Note: Descriptions are shown in the official language in which they were submitted.
CA 02590769 2007-06-06
ELECTRICAL PANEL INPUT INTERLOCK ASSEMBLY
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the benefit of U.S. Ser. No. 60/804,016, filed June 6,
2006, the
disclosure of which is incorporated herein by reference.
SACKGRbUND OF THE E!EUNTION
The present invention relates generally to electrical panels and, more
particularly, to a power
supply or input interlock assembly constructed to electrically isolate
different inputs connected to an
eleatrical panel.
Electrical panels, breaker boxes, or load centers frequently include a main
contactor, switch,
or breaker, which electrically isolates a series of load breakers from a
utility power input.
Occasionally, such load panels are configured to receive another input power
source, such as from a
generator, to provide electrical power to the individual loads in the event of
a utility power failure.
During interruption of utility power, the generator supplies power to the load
center, which the load
center distributes to the selected or designated circuits of the building.
Before activating the
generator power supply, the main switch must be disconnected or turned "OFF'
to prevent the
generator power from back-feeding through the utility conductors. A user must
manually configure
the switches of the load center to electrically connect the generator power
with the series of loads
and electrically isolate the utility power from the generator power, and vice-
versa. In order to
maintain electrical isolation between the generator power input and the
utility power input, the
connection/disconnection of the utility power supply and generator power
supply must be performed
in a specific sequence to ensure electrical isolation of the respective input
powers. An interlock
system has been developed for carrying out this function, and is shown and
described in Flegel U.S.
Patent 6,621,689 issued Septennber 16, 2003, the disclosure of which is hereby
incorporated by
reference. While the system shown in the `689 patent controls operation of a
main power supply
ON/OFF switch and an auxiliary power supply ON/OFF switch, it contains no
provisions for
controlling operation of neutral switches associated with the main and
auxiliary power supplies.
When a bonded neutral generator is connected to the wiring system of a
building, the
grounding conductor and the neutral conductor are connected in two places
within the system. This
allows for the return of current back to the generator to flow on both the
grounding conductor and on
the neutral conductor. Having normal current flow on the grounding conductor
limits the ability of
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the grounding conductor to pet'form its safety function, and is therefore
undesarable, Switching the
neutral conductor(s) when switching the power supply conductors prevents any
neutral current from
flowing on the grounding conductor_ Furthermore, it is important to control
the sequence of
operation of the generator and utility neutral switches when switching between
power sources, since
supplying power to a device without a neutral may result in failure of the
device due to an
unpredictable voltage being supplied to the device, To prevent this
occurrence, the switching
sequence is as follows when switching from main utility power to generator
power:
1. Turn off main power;
2. Turn off main neutral;
3. Turn on generator neutral;
4. Turn on generator power.
This sequence is reversed when switching from generator power to utility
power.
For the above reasons, it is desirable to provide an input interlock assembly
that ensures
electrical isolation of the utility power and the generator power during a
transfer of the input power
from one source to another, and which controls the sequence of operation of
neuttal switches
associated with the utility and generator power supplies.
SUMMARY OF THE INVENTION
The present invention is directed to a main power switch interlock assembly
that prevents
inadvertent simultaneous electrical connection of both a utility power input
and an input from an
alternate power supply, such as a generator, to a breaker panel, and controls
actuation of utility and
alternate power supply neutral switches.
A system and method of controlling operation of a plurality of electrical
panel switches
includes an assembly having an interlock. The interlock has a first position
that allows power to be
supplied to the electrical panel from one power source, such as utility power
or an alternate power
supply such as a generator, and prevents the supply of power to the electrical
panel from the other
power source, The interlock also includes a feature that controls movement of
neutral switches
associated with the alternate power supply and utility power inputs to ensure
that the neutral
connection of the alternate power supply is ON when the alternate power supply
is activated, and
that the alternate power supply neutral connection is OFF and the utility
neutral is ON when the
utility power supply is activated.
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Various other features, objects and advantages of the present invention will
be made apparent
from the following detailed description of the drawing figures.
BRIEF DESCRIPTION OF THE DRAWINGS
The drawings illustrate one preferred embodiment presently contemplated for
carrying out
the present invention.
In the drawings:
Fig. 1 is a perspective view of an exemplary load center asserzably having one
embodiment of
an interlock assembly according to the present invention.
Fig. 2 is an elevational view of the load center assembly shown in Fig. 1 with
the interlock
assembly configured to enable the supply of utility power to the loads
interconnected with the load
center assembly.
Fig. 3 is an elevational view of the load center assembly shown in Fig. 2 with
the utility
power and alternate power disconnected from the loads interconnected with the
load center
assembly.
Fig. 4 is an elevational view of the load center assembly shown in Fig. 3 with
the interlock
assembly configured to enable a pair of neutral switches to switch OFF the
utility neutral and switch
ON the generator neutral.
Fig. 5 is an elevational view of the load center assembly of Fig. 4 showing
movement of a
switch associated with the alternate power input connected to the loads
interconnected with the load
center assembly.
Fig. 6 shows the load center assembly of Fig, l with the cover removed
therefrom.
Fig. 7 shows the load center assembly of Fig. I with the switches positioned
such that utility
power is isolated from the load terminal bars and power from the alternate
power supply is
connected thereto.
Fig. 8 is an elevational view of a load center assembly equipped with another
embodiment of
an interlock assembly according to the invention.
Fig, 9 is an elevational view of the load center assembly shown in Fig. 8 with
the switches
positioned such that utility power and power from the alternate power supply
are both isolated from
the load terminal bars and the utility neutral ON and the alternate power
supply neutral OFF.
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Fig. 10 is an elevational view of the load center assembly shown in Fig. 9
with the switches
and interlock assembly configured to prevent connection of utility power to
the load terminal bars
and allow connection of altennate power thereto.
Fig. 11 is an elevationial view of the load center assembly shown in Fig. 10
with the switches
and interlock assembly positioned such that alternate power is conununicated
to the load terminal
bars and the utility neutral OFF and the alternate power supply neutral ON.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Fig. 1 shows a load center assembly 10 according to one embodiment of the
present
invention, which is configured to supply power to a series of electrical
circuits from one of at least
two power sources. Representatively, load center assembly 10 controls the
supply of power to the
electrical circuits from a primary power supply, such as utility power, and an
alternate or secondary
power source which is adapted to supply power in the event power from the
primary power supply is
unavailable. Typically, the alternate or secondary power source is an
electrical generator, although it
is understood that any other source of secondary or alternate power may be
employed. The
following description utilizes terminology which makes reference in various
instances to a generator,
and it is understood that such terminology is used for the sake the
convenience and that the term
"gcnerator" is meant to encompass any secondary or alternate power source, and
is not limited to a
generator as the alternate power source.
Load center assembly 10 includes a cover 12 having a door 14 pivotably
connected thereto.
Cover 12 includes a series of knockouts 16 constructed to be removed as load
breakers are added to
load center assembly 10. A main switch 18 passes through cover 12 and is
constructed to be
connected to a utility power input. A generator neutral switch 20, generator
switch 21, and a utility
neutral switch 22 are constructed to be electrically connected to load center
assembly 10. An
interlock assembly 24 is connected to load center assembly 10 and prevents the
inadvertent
connection of the utility power input via main switch 18 and generator power
input via generator
switch 21 from being concurrently connected to a the toad terminals of load
center assembly 10. As
will be explained, interlock assembly 24 also controls the movetnent of
neutral switches 20 and 22
relative to main switch 18 and generator switch 21, to ensure that the
switches are actuated in the
correct sequence.
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Fig. 2 shows load center assembly 10 with interlock assembly 24 configured to
enable the
supply of utility power via main switch 18 such that the loads connected to
load center assembly 10
are powered by utility power. Interlock assembly 24 is positioned to prevent
the connection of
generator power communicated via generator switch 21 to the load terminal bars
of load center
assembly 10, by preventing movement of generator switch 21 to the ON position.
Interlock assembly
24 includes a first movable interlock 26 and a secottd movable interlock 28,
the operation of which
are described in Figs. 2 through 7.
Referring to Fig. 3, during interruption of utility power, a user translates
switch handle 30 of
main switch 1$ from an ON position 32, as shown in Fig. 2, to the OFF position
34, as shown in Fig.
3. Such manipulation electrically isolates the load terminals and generator
switch 21 from utility
power conductors connected to main switch 18. With switch 18 positioned in OFF
position 34,
movable interlock 26 is manually translated upwardly in the direction of arrow
36 (shown in Fig. 4),
thereby preventing movement of handle 30 away from the OFF position 34 and
locking handle 30
OFF (shown in Fig. 4). A tab 38 of interlock 26 also moves in direction 36 and
passes behind an
interlock assembly retainer plate 40. Prior to movement of interlock 26 in
direction 36, tab 38
extends into the throw of a switch handle 42 of generator neutral switch 20.
Accordingly, prior to
movement of interlock 26 in direction 36, tab 38 prevents the movement of
generator neutral switch
away from the generator neutral OFF position. Because generator neutral switch
handle 42 and
the switch handle 44 of utility neutral switch 22 are intercotutected for
linear movement together by
20 an in-line interlock assembly 46, tab 38 also prevents the movement of
utility neutral switch 22 away
from the utility neutral ON position.
As shown in Fig. 4, translation of interlock 26 in direction 36 relative to
interlock assembly
plate 40 obstructs handle 30 of main switch 18, thereby preventing utility
power from being
communicated to the load terminal bars of load center assembly 10, At the same
time, tab 38
translates in direction 36 behind interlock assembly plate 40 and out of the
way of the throw of
handle 42 of generator neutral switch 20. Accordingly, when handle 30 of main
switch 18 is located
in OFF position 34, generator neutral switch 20 can be moved to the ON
position by translation of
handle 42. Due to the presence of in-line interlock assembly 46 between switch
handle 42 azxd switch
handle 44 of generator neutral switch 20 and utility neutral switch 22,
respectively, generator neutral
switch 20 is operable to an ON position and utility neutral switch 22 is moved
to an OFF position,
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represented as position 48 as shown in Fig. 4. This connects the generator
neutral to a neutral bar of
load center assembly 10 common to switches 20 and 22,
Representatively, in-line anterlock assembly 46 may have a construction as is
shown and
described in Flegel US patent 6,031,193 issued February 29, 2000 or Flegel US
patent 6,927,349
issued August 9, 2005, the disclosures of which are hereby incorporated by
reference.
Referring to Fig. 3 and Fig. 4, second interlock 28 is movable from a first
position 52, as
shown in Fig. 3, to a second position 54, as shown in Fig. 4, when generator
neutral switch handle 42
is in the ON position and utility neutral switch handle 44 is in the OFF
position. As shown in Fig. 3,
when second interlock 28 is located in first position 52, interlock 28
obstructs the operation of a
switch handle 56 of generator switch 21. Also, interlock 28 is prevented from
moving by a post 55 of
interlock assembly 46. When second interlock 28 is allowed to be moved to
second position 54 by
the change in position of interlock assembly 46, as shown in h'ig. 4, a switch
handle 56 of generator
switch 21 is operable to connect the generator power input to the input of
load center assembly 10.
Accordingly, when switch handles 30, 42, 44, and 56 are oriented in the
positions as shown in Fig. 5,
load center assembly 10 is electrically connected to a generator power input
and electrically isolated
from a utility power input, and the generator neutral is connected to the
neutral of load center
assembly 10, Furthetinore, interlock assembly 24 prevents the reconfiguration
of switches 18, 20,
22, and 21 to such an orientation wherein generator power and utility power
are concurrently
delivered to the load terminal bars of load center assembly 10. As such,
interlock assembly 24 is
constructed to sequence the operation of switches 18, 20, 22, and 21 and
thereby control and
segregate the input power delivered to the load terminal bars of load center
assembly 10 relative to
the neutral connections of the utility and generator power supplies.
As shown in Fig. 6, removal of cover 12 from load center assembly 10 exposes a
series of
terminal bars 58 located therebehind, Terminal bars 58 include a first and a
second neutral bar 60, 62
and a first and a second hot lead terminal bar 64, 66, respectively. A neutral
connector plate 68
extends behind interlock assembly 24 and electrically connects first neutral
bar 60 and second
neutral bar 62. Generator neutral switch 20 is electrically connected to
neutral connector plate 68, as
is utility neutral switch 22. Generator switch 21 is electrioally connected to
hot ternunal bars 64 and
66.
Main switch 18 includes a first input terminal 70 and a second input terminal
72 oonstructed
to be electrically connected to a utility power conductor connected to load
center assembly 10. When
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switch handle 30 of main switch 18 is positioned in an ON position, as shown
in Fig. 6, utility power
communicated to input terminal 70 and input t e r m i n a l 72 is
comm,uiucated t } u o u g h main switch I S
to hot terminal bar 64 and hot terminal bar 66, thereby communicating utility
power to the load
breakers connected to load center assembly 10, Referring to Fig. 7, switch
handle 30 o#'main switch
18 is moved to an OFF position, thereby electrically isolating input terminal
70 and input terminal
72 of main switch 18 from hot terminal bars 64, 66. Movement of first
interlock 26 of interlock
assembly 24 prevents switch handle 30 from being moved to an ON position and
translates tab 38 of
interlock assembly 24 such that switch handle 42 of generator neutral switch
20 is free to be moved
to an ON position, which also results in movement of switch handle 44 of
utility neutral switch 22 to
an OFF position. Translation of second interlock 28 relative to interlock
assembly 46 allows switch
handle 56 of generator switch 21 to be moved to an ON position. In this
manner, generator switch 21
is connected to hot terminal bars 64 and 66 and the generator neutral switch
20 is connected to
neutraI bars 60 and 62 via neutral connector plate 68, Accordingly, when
switch handles 30, 42, 44,
and 56 are oriented in the positions shown in Fig. 7, generator power is
communicated through
generator switch 21 to hot terminal bars 64, 66 and generator neutral is
communicated through
generator neutral switch 20 to neutral plate 68, thereby electrically
connecting loads connected to
either of first hot terminal bar 64 or second hot terminal bar 66 to the
generator-provided input
power associated with generator switch 21, This also isolates utility neutral
from generator neutral
and thus, the neutrals cannot be switched back unless generator and utility
supply switches are both
OFF. Generator power delivered to load center assembly 10 and communicated to
hot terminal bar
64 and hot terminal bar 66 is electrically isolated from utility input
terminals 70, 72 of main switch
18. Interlock assembly 24 prevents the concurrent electrical connection of
generator switch 21 and
main switch 18 with hot terminal bars 64, 66. Such a construction electrically
isolates utility input
terminals 70 and 72 from hot terminal bars 64, 66 when generator power is
supplied, thereby
preventing communication of generator-derived power beyond load center
assembly 10 via utility
conductors connected thereto.
Fig. 8 shows another breaker box assembly or load center 78 according to
another
embodiment of the present invention. Load center 78 includes an altemate
embodiment of an
interlock assembly 80 according to the present invention. Interlock assembly
80 is disposed between
a utility or main switch 82 and a series of switches mounted to load center
78. Main switch 82
includes a first input terminal 86 and a second input terminal 88 constructed
to be electrically
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connected to utility power conductors, respectively. A switch 82 electrically
connects input terrninals
86, 88 with hot terminal bars 92, 94. Interlock assembly 80 includes a movable
interlock 96 that has
a tab 98 extending therefrom. Tab 98 extends into a tltrovu of a switch handle
100 of generator
neutral switch 102, thereby preventing movement of generator neutral switch
handle 100 when tab
98 is so positioned.
An in-line interlock assembly 104 extends between generator neutral switch
handle 100 and a
switch handle 106 of a utility neutral switch 108 such that genera.tor neutral
switch handle 100 and
utility neutral switch handle 106 are operatively associated such that neither
switch can be
independently moved. A bracket 110 is connected to connector assembly 104 and
disposed between
switch handle 100 and switch handle 106. Bracket 110 includes a first
extension 112, which
interferingly engages another tab 114 of interlock 96. First extension 112 and
tab 114 are associated
to allow movement of interlock 96 into a space 116 formed between first
extensi8n 112 and switch
handle 100 of generator neutral switch 102. Such an orientation eqsures a snug
engagement
therebetween, thereby preventing movement of switch handle 100 or switch
handle 106 relative to
interlock 96 when tabs 98, 114 are disposed in space 116.
Bracket 110 includes a second extension 118, which extends in a direction
generally opposite
the direction of extension of first extension 112. Second extension 118 is
operatively connected to a
switch handle 120 of a generator switch 122. Generator switch 122 is
electrically connected to hot
terminal bars 92, 94. Neutral switches 102 and 108 are electrically connected
to neutra] bar 60 and
62 via neutral connector plate 68. Accordingly, regardless of which side of
load center 78 load
circuits are connected, generator power can be utilized to power any desired
load connected to load
center 78.
As shown in Fig. 9, switch handle 90 of main switch 82 is located in an OFF
position,
thereby electrically isolating hot terminal bars 92, 94 from the utility power
connected to input
terminals 86 and 88 of load center 78. Positioning of switch handle 90 in the
OFF position allows
interlock 96 to be moved in a direction, indicated by arrow 124 (shown in Fig.
10), toward switch
handle 90. As interlock 96 moves in direction 124, tabs 98, 114 translate
therewith and out of
interfering engagemeztt with switch handles 100, 106 and 120.
As shown in Fig, 10, when switch handle 90 is located in an OFF position and
interlock 96 is
displaced in direction 124, interlock 96 prevents switch handle 90 from being
moved to the ON
position. Accordingly, when interlock 96 is oriented in the position shown in
Fig. 10, switch 82 is
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configured to electrically isolate the utility power input terminals 86, 88
from hot terminal bars 92,
94, thereby electrically isolating utility conductors connected to inputs 86,
88 from generator power
communicated to hot terminal bars 92, 94. Furthermore, as shown in Fig. 10,
when interlock 96 is
positioned to obstruct handle 90, tabs 98, 114 translate in direction 124 and
pass behind a cover plate
126 of interlock assembly 80. Switches handles 100, 106, 120 are
intercontnected via bracket I 10
such that, when interlock 96 is translated in direction 124, as shown in Fig.
10, movement of any of
switch handles 100, 106, 120 in a transverse direction, indicated by arrow
128, elactricaIly connects
generator input power from generator switch 122 to hot terminal bars 92, 94,
respectively, and
connects the generator neutral switch 102 to neutral bar 60. The connection of
generator switch
handle 120 to bracket 110 is positioned such that, as bracket I 10 is
transiated lateralIy, the utility
neutral switch handle 106 is first moved OFF and the generator neutral switch
handle 100 is moved
ON, before generator switch handle 120 is moved ON. SimilarIy, the generator
switch handle is
tumed OFF before the generator neutral is switched OFF. This ensures proper
sequence of operation
of the switches as the supply of power from utility to generator is
transfetred.
As shown in Fig. 11, bracket l 10 has been translated in direction 128,
thereby moving switch
handles 100, 106, 120 to an ON position, and electrically connecting generator
power communicated
to generator switch 122 to hot terminal bars 92, 94 and connecting generator
neutral switch 102 to
neutral bars 60, 62. Furthermore, when generator power is communicated through
generator
switches 122 to hot terminai bars 92, 94, movable interlock 96 of interlock
assembly 80 prevents the
electrical connection of utility power input terminals 86, 88 of utility
switch 82 with hot terminal
bars 92, 94, thereby electrically isolating input terminals 86 and 88 from
power communicated to
load center 78 via the utility power source. Understandably, to convert load
center 78 from utility-
derived power to generator-derived power, a user must simply orient handle 90
of main switch 82 in
the OFF position, translate interlock 96 in direction 124, and translate
switch handles 100 and 120 to
an ON position, thereby electrically connecting the generator-type power to
hot terminal bars 92, 94
and the neutral to neutral bars 60, 62. Such a configuration allows a user to
conveniently and
expeditiously configure load center 78 to power desired loads froxn a desired
input power supply,
A system and method of interlocking a plurality of electrical panel switches
includes an
interlock assembly having an interlock. The interlock has a first position
that allows connection of
one of utility power and generator power to the electrical panel and prevents
connection of the other
of the utility power and generator power, The interlock has a second position
that allows connection
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of the other of the utility power and generator power and prevents connection
of one of the utility
power and generator power to the electrical panel.
Various alternatives are oontemplated as being within the scope of the
following claims
particularly pointing out and distinctly claiming the subject matter regarded
as the invention.
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