Motor control centers and interlock systems for electrical equipment

Abstract

The present application relates to a motor control center and an interlocking system for electrical equipment. The motor control center includes an enclosure having an isolating switch, a main contactor device, and a grounding switch device. The isolating switch can be selectively manually operated between a connected state and a disconnected state. The main contactor device can be selectively operated between a conductive state and a non-conductive state. The grounding switch device can be manually operated from an open ungrounded state to a closed grounded state, in which the main contactor device is electrically disconnected from the grounding path in the open ungrounded state, and in the closed grounded state, the main contactor device is electrically connected to the grounding path. The motor control center also includes a first interlocking device operably connected between the isolating switch and the grounding switch device, wherein when the grounding switch device is in the grounded state, the first interlocking device prevents the isolating switch from moving from the disconnected state to the connected state.

Description

Background Art

[0001] Motor control centers (MCCs) for distributing power to electric motors are well known in the art. Such motor control centers are connected to a power source, typically a three-phase AC power source. A main contactor within the MCC is operable to selectively conduct power to a load, such as one or more motors, or to disconnect power from the load. The motor control center also includes an isolating switch or "isolator" electrically positioned upstream relative to the main contactor. The isolator is manually operated by an isolating switch handle. When the isolating switch handle is moved to the open (off) position (typically the "down" position), the isolating switch opens to disconnect the main contactor and other downstream components of the motor control center from the input power source. When the handle is moved to the closed (on) position (typically the "up" position), the isolating switch closes to connect the main contactor and other downstream components to the power source.

[0002] During maintenance of such motor control centers, maintenance personnel are expected to ground (earth) the main contactor and other components within the motor control center. A grounding switch is provided for this purpose. The grounding switch is selectively operable between a closed position or "grounded" position, in which the grounding switch connects the main contactor to the ground path, and an open position or "ungrounded" position, in which the grounding switch opens the ground path circuit to disconnect the main contactor from the ground path.

[0003] For safe operation of a motor control center, it is necessary to prevent the grounding switch from its open position to its closed position while the isolator switch is in its closed condition, which could result in a dangerous and destructive short circuit. For the same reason, it is necessary to prevent the isolator switch from its open position to its closed position while the grounding switch is already in its closed condition. To prevent the grounding switch and the isolator switch from being in a conductive state simultaneously, known motor control centers include a key-based interlock device that uses the same single key for unlocking both the isolator switch and the grounding switch (allowing operation of both). When the interlock device is in the interlock device's unlocked condition, the key is captured in the key interlock device, preventing a user from closing the isolator switch when the grounding switch is already closed, or vice versa.

[0004] While generally safe and effective, these key-based interlock systems are suboptimal because keys can be lost, operators must perform additional steps, and there is no safety redundancy in the sense that if the key interlock device fails or otherwise becomes improperly unlocked, an undesirable situation can occur where both the grounding switch and the isolator switch are simultaneously in a closed state. Therefore, a need has been identified for a new and improved grounding switch interlock system for motor control centers and other industrial electrical equipment that overcomes the above and other deficiencies associated with known key-based interlock devices while providing superior overall results. Summary of the Invention

[0005] According to one aspect of the present invention, a motor control center includes an enclosure including an isolating switch, a main contactor assembly, and an earthing switch assembly. The isolating switch is selectively manually operable between a connected state and a disconnected state, wherein the isolating switch in the connected state is adapted to conduct power from an associated power source to the main contactor assembly, and wherein the isolating switch in the disconnected state interrupts conduction of power from the associated power source to the main contactor assembly. The main contactor assembly is selectively operable between a conductive state and a non-conductive state, wherein when the main contactor assembly is in the conductive state of the main contactor assembly, the main contactor assembly is adapted to electrically connect the isolating switch to the earthing switch assembly and an associated electrical load, and wherein when the main contactor assembly is in the non-conductive state of the main contactor assembly, the main contactor assembly disconnects the isolating switch from the earthing switch assembly and the associated electrical load. The earthing switch assembly is manually operable from an open, non-grounded state to a closed, earthed state, wherein in the open, non-grounded state, the main contactor is electrically disconnected from a grounding path, and in the closed, earthed state, the main contactor is electrically connected to the grounding path. The motor control center also includes a first interlock device operably connected between the disconnect switch and the grounding switch device, wherein the first interlock device prevents the disconnect switch from moving from the disconnected state to the connected state when the grounding switch device is in the grounded state.

[0006] According to another aspect of the present disclosure, an interlock system for electrical equipment includes an isolating switch that is selectively manually operable between a connected state and a disconnected state, wherein the isolating switch in its connected state is adapted to conduct electricity, and wherein the isolating switch in its disconnected state interrupts the conduction of electricity. A handle is operably connected to the isolating switch, and the handle is movable between an "off" position corresponding to the disconnected state of the isolating switch and an "on" position corresponding to the connected state of the isolating switch. The grounding switch assembly is manually operable from an open, ungrounded state to a closed, grounded state, in which the main isolating switch is electrically disconnected from the grounding path, and in which the isolating switch is electrically connected to the grounding path. An interlock plunger is operably connected to the handle via an interlock linkage and is movable between a retracted position corresponding to the "off" position of the handle and an extended position corresponding to the "on" position of the handle, and is movable between the retracted and extended positions. The interlock plunger prevents the grounding switchgear from moving from an open, ungrounded state of the grounding switchgear to a closed, grounded state of the grounding switchgear when the interlock plunger is in the extended position of the interlock plunger. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a front view of a motor control center including an integrated interlock system according to an embodiment of the present invention.

[0008] Figure 2 yes Figure 1 Isometric view of a motor control center.

[0009] Figure 3A yes Figure 1 and Figure 2 A partial isometric view of a motor control center showing an isolator-grounding switch interlock device as part of an integrated interlock system, wherein the grounding switch device is shown in its closed state or grounded (conductive) state and the isolator-grounding switch interlock device is shown in its unlocked (disengaged) condition or state.

[0010] Figure 3B Similar to Figure 3A , but showing the isolator earthing switch interlock device from another perspective.

[0011] Figure 3C is an enlarged fragmentary view of a key interlock which may optionally form part of the integrated interlock system of the present invention, wherein the key interlock is shown in its unlocked (disengaged) state.

[0012] Figure 3D Similar to Figure 3A, but the earthing switchgear is shown in its open or ungrounded (non-conductive) state and the earthing switch interlock is shown in its locked (engaged) condition or state.

[0013] Figure 3E Similar to Figure 3D , but showing the isolator earthing switch interlock from a different perspective (and also showing the key interlock in its locked (engaged) state).

[0014] Figure 3F yes Figure 3C An enlarged view of the key interlock device in its locked (engaged) state.

[0015] Figure 4 yes Figure 1 and Figure 2 A partial side view of a motor control center and illustrating that the integrated interlock system can optionally include both an isolator handle linkage grounding switch interlock system and a shared key grounding switch interlock system.

[0016] Figure 5 It is a diagram with Figures 1 to 3F Schematic diagram of the corresponding integrated interlocking system.

[0017] Figure 6 A motor control center including an integrated grounding switch interlock system according to an alternative embodiment of the present invention is shown. DETAILED DESCRIPTION

[0018] Figure 1 is a front plan view of a motor control center M or "MCC" including an integrated earthing switch interlock system IK in accordance with an embodiment of the present invention, with certain panels and components removed for clarity. Figure 2 This is an isometric view of the motor control center M. Figure 1 and Figure 2 In both cases, the motor control center M includes a cabinet or enclosure E that houses power switches and power distribution components PX for supplying power to one or more loads, such as one or more motors, etc. More specifically, the MCC includes an isolating switch IS (sometimes referred to as an "isolator switch" or "isolator") that selectively connects the MCC to the power supply via terminals T (see Figure 5 ) provides power, such as three-phase AC power connection and disconnection (isolation).

[0019] The isolator IS includes and / or is operably connected to an isolator handle IH, through which an operator manually controls the operational state of the isolator switch IS. The isolator handle IH pivots between at least a first or "off" position (typically pivoted downward to its maximum extent), as shown. In the first or "off" position, the isolator switch IS is open and disconnected from the input power terminals T (disconnected state), and a second or "on" position (typically pivoted upward to its maximum extent). In the second or "on" position, the isolator switch IS is closed or connected to the input power terminals T (connected state). The isolator handle IH is operably mechanically connected to the isolator switch IS via an isolator switch linkage ISL, which opens and closes the isolator IS in response to movement of the handle IH between its first and second operational positions.

[0020] The motor control center M also includes a main contactor device CX that can be electromechanically or otherwise operated to selectively conduct power from the source terminal T to an associated motor or other load (closed state or conductive state) or to disconnect the motor or other load from the power supplied by the terminal T (open state or non-conductive state). The main contactor device CX includes a plurality of contactors corresponding in number to the number of electrical phases (i.e., three contactors X1, X2, X3 for three-phase power), the plurality of contactors being electrically connected on the input side to the power supply terminal T (when the isolator IS is closed), and the plurality of contactors being connected or adapted to be connected on the output side or "load side" to the motor or other load LD being powered ( Figure 5 When the main contactor CX is in its conductive state, the contactors X1 to X3 are closed and conduct power from the disconnect switch IS to the motor or other load LD. When the main contactor CX is in its non-conductive state, the contactors X1 to X3 are open and interrupt the flow of power from the disconnect switch IS to the motor or other load LD. As is generally known in the art, a contactor interlock linkage CXL is provided between the isolator handle and the main contactor assembly CX to at least ensure that the disconnect switch IS cannot be opened or closed when the main contactor assembly CX is in its closed (conductive) state.

[0021] The motor control center M further includes a grounding switch or grounding switch device GS that can be selectively manually operated to connect the load side of the main contactor CX (i.e., the load side of the contactors X1 to X3 of the main contactor CX) to the ground path GP ( Figure 5 ) to release the voltage from the motor control center for safety. Figures 3A to 3FThe grounding switch GS is shown separately and includes at least one grounding terminal GT and typically a plurality of grounding terminals GT (GT1 to GT3), which are equal in number to the contactors and are electrically connected to the load sides of the contactors X1 to X3, respectively. The grounding switch GS also includes at least one grounding switch contact GC and typically a plurality of grounding switch contacts GC (GC1, GC2, GC3), which are equal in number to the grounding terminals GT1 to GT3. When the grounding switch GS is closed (e.g. Figure 3A and Figure 3B The grounding switch contacts GC1 to GC3 are in contact with and electrically connected to the ground terminals GT1 to GT3, respectively, to connect the ground terminals GT1 to GT3 (and the associated contactors X1 to X3 connected to the ground terminals GT1 to GT3, respectively) to the ground path GP. Figure 3D and Figure 3E In the "ungrounded state" shown in FIG1 , the grounding switch contacts GC1 to GC3 are respectively separated from the grounding terminals GT1 to GT3 to disconnect the grounding terminals GT1 to GT3 (and the associated contactors X1 to X3 connected to the grounding terminals GT1 to GT3, respectively) from the grounding path GP.

[0022] By specifically continuing to refer to Figures 3A to 3F It can be observed that the grounding switch GS includes a rotatable grounding shaft GSX connected to a grounding path GP. Grounding switch contacts GC1 to GC3 are connected to the grounding shaft GSX and rotate therewith. Rotation of the grounding shaft GSX in a first angular direction moves the grounding switch contacts GC1 to GC3 into contact with the corresponding grounding terminals GT1 to GT3, thereby connecting to and completing the grounding path GP. Rotation of the grounding shaft GSX in an opposite, second angular direction separates the grounding switch contacts GC1 to GC3 from the corresponding grounding terminals GT1 to GT3, thereby opening or interrupting the grounding path GP.

[0023] The grounding shaft GSX can be manually rotated using a wrench or other tool TL, which is removably connected to a rotatable torque input head HX. The torque input head HX is connected to an input gear GR1 that is drivingly engaged with the grounding shaft GSX and rotates together with the input gear GR1, so that manual rotation of the torque input head HX in the first and second directions causes the input gear GR1 to rotate accordingly and also causes the grounding shaft GSX to rotate accordingly in the first and second angular directions. As shown herein, the input gear GR1 is non-rotatably connected to an input shaft GR1X, which is rotatably supported relative to the enclosure E, and the torque input head HX is non-rotatably connected to the input shaft GR1X and / or forms a part of the input shaft GR1X. In the embodiment shown, a main gear GR2, such as a bevel gear, is non-rotatably connected to the grounding shaft GSX and engaged with the input gear GR1, which acts as a pinion to drive the main gear GR2 and the grounding shaft GSX in the first and second angular directions to open and close the grounding contacts GC1 to GC3. The grounding switchgear GS also includes an output or driven gear GR3 that is drivingly engaged with the main gear GR2 and rotates in opposite first and second directions in response to rotation of the main gear GR2. Specifically, the driven gear GR3 rotates in opposite directions relative to the input gear GR1, such that when the input gear GR1 rotates in the first and second directions, the driven gear GR3 rotates in the opposite second and first directions, respectively. Gears GR1 through GR3 define a grounding switchgear gear train.

[0024] The grounding switch GS includes at least one interlocking device, and optionally includes a first interlocking device and a second interlocking device, for preventing the grounding switch contacts GC1 to GC3 from closing when the isolator switch IS is closed, and for preventing the isolator switch IS from closing when the grounding switch contacts GC1 to GC3 are closed. In particular, the grounding switch includes a first interlocking device IX1 (sometimes referred to herein as an "isolator interlocking device") and optionally also includes a second interlocking device IX2 (sometimes referred to herein as a "key interlocking device").

[0025] The first (isolator) interlocking device IX1 includes a first locking base or first locking block B1, which is non-rotatably connected to the driven gear GR3. As shown, the driven gear GR3 is non-rotatably connected to the output shaft GR3X, which is rotatably supported relative to the enclosure E, and the first locking block B1 is non-rotatably connected to the output shaft GR3X so as to rotate in unison with the driven gear GR3. The first locking block B1 can be non-circular and include multiple flat surfaces. The first locking block B1 includes a first locking recess RC1.

[0026] The first interlock device IX1 further includes an interlock member, such as an interlock member or interlock plunger LP1, connected to an isolator switch interlock linkage IXL, which is operatively connected to the isolator switch handle IH. Due to the interlock linkage IXL, movement of the isolator switch handle IH from the first (off) position to the second (on) position causes movement of the interlock plunger LP1 in a first direction D1 toward the first locking block B1 (downward in a typical installation) to the deployed position or extended position, as shown in FIG. Figure 3D and Figure 3E Conversely, when the isolator switch handle IH is moved from its second (connected) position toward its first (closed) position, the interlock linkage IXL causes the interlock plunger LP1 to move in a second direction D2 opposite to the first direction D1 and away from the first locking block B1 (upward in a typical installation) to a position as shown in FIG. Figure 3A Shown in stored or retracted position.

[0027] The first locking block B1 is shaped and dimensioned to block and prevent movement of the interlock plunger LP1 in the first direction D1 for all angular positions of the first locking block B1 except when the locking recess RC1 is in a selected plunger receiving position in which the locking recess RC1 is aligned or in registration with the interlock plunger LP1. When the locking plunger LP2 is in the first locking recess RC1, the isolator interlock IX1 is in its "engaged" position in which the isolator interlock IX1 prevents operation of the grounding switchgear GS, and when the locking plunger LP2 is retracted and withdrawn from the locking recess RC1, the isolator interlock IX1 is in its "disengaged" position in which the isolator interlock IX1 allows operation of the grounding switchgear GS.

[0028] When the isolator interlock is disengaged and moving toward its engaged position, contact between interlock plunger LP1 and first locking block B1 prevents movement of locking plunger LP1 in a first direction D1, which in turn prevents movement of the isolator handle to its "on" (conductive) position, unless locking recess RC1 is aligned with locking plunger LP2. First locking block B1 is keyed to a selected angular position on output shaft GR3X such that locking recess RC1 is only positioned in a locking plunger-receiving position. In this position, locking recess RC1 is aligned with interlock plunger LP1 and is open to receive interlock plunger LP1 when grounding switch GS is in or disposed in its open (non-conductive) position, i.e., when grounding contacts GC1 to GC3 are open. Therefore, when locking recess RC1 is aligned with interlock plunger LP1, interlock plunger LP1 can move in direction D1 into locking recess RC1 (to engage isolator interlock IX1), allowing the isolator handle IH to move to its "on" (conductive) position. Furthermore, those skilled in the art will recognize that the locking recess RC1 is shaped and dimensioned to receive the interlock plunger LP1 therein in such a manner that, when the isolator interlock system IX1 is engaged, the interlock plunger LP1 abuts the first locking block B1 and prevents rotation of the first locking block B1, thereby also preventing rotation of the driven gear GR3, the master gear GR2, and the grounding shaft GSX when the interlock plunger LP1 is received and seated in the locking recess RC1. In this manner, the grounding switch is restrained in its open (non-conductive) state when the isolator handle IH is in its second (connecting) position, corresponding to the closed (conductive) state of the isolator switch IS, preventing the grounding contacts GC1 to GC3 from closing when the isolator switch is in the conductive state. The interlock plunger LP1 is shown as being linearly moved in opposite first and second directions D1 and D2 by the interlock linkage IX1, but those skilled in the art will recognize that the interlock plunger may alternatively move along a non-linear path between its retracted and deployed positions.

[0029] The second (key) interlocking device IX2 similarly includes a second locking member or second locking block B2, which is non-rotatably connected to the input gear GR1. As shown, the input gear GR1 is non-rotatably connected to the input shaft GR1X, which is rotatably supported relative to the enclosure E, and the second locking block B2 is non-rotatably connected to the input shaft GR1X so as to be non-rotatably coupled to the input gear GR1 and rotate in unison with the input gear GR1. The second locking block B2 can be non-circular and include a plurality of flat surfaces. The second locking block B2 includes a second locking recess RC2 (see Figure 3E and Figure 3F ).

[0030] The key interlocking device IX2 further comprises an interlocking member, such as a key locking plunger or other locking member LP2 connected to a key locking assembly LA, which is operable by means of a removable key K. The locking assembly LA is secured to the enclosure E. When the key K is operably engaged in the locking assembly LA, rotational movement of the key K in a first direction from a first (unlocked) position to a second (locked) position causes the locking member LP2 to rotate in an extension direction X1 ( Figure 3C ) toward the second locking block B2 (downward in the illustrated embodiment) to Figure 3E and Figure 3F Conversely, when the key K is rotated in a second, opposite direction from the second (locked) position to the first (unlocked) position, the locking assembly LA causes the locking member LP2 to retract in a direction X2 (opposite to the extension direction X1) away from the second locking block B2 (upward in the illustrated embodiment). Figure 3C ) Figures 3A to 3C 1 and 2. The second locking block B2 is shaped and dimensioned to be contacted by the locking member LP2 and to block and prevent the locking member LP2 from moving in the extension direction X1 to its extended position for all angular positions of the second locking block B2 except when the second locking recess RC2 of the second locking block B2 is in a selected plunger receiving position in which the recess RC2 is aligned or aligned with the locking member LP2. The second locking block B2 is keyed on the input shaft GR1X in a selected angular position so that the second locking recess RC2 is only in its receiving position in which the second locking recess RC2 is aligned with the locking member LP2 and the second locking recess RC2 is open to receive the locking member LP2 when the earthing switch GS is in its open (non-conducting) position, i.e. when the earthing contacts GC1 to GC3 are open. Figure 3E and Figure 3F As shown. Furthermore, those skilled in the art will recognize that the locking recess RC2 is shaped and dimensioned to receive the locking member LP2 therein in such a manner that, when the locking member LP2 is received and seated in the locking recess RC2, the locking member LP2 abuts the second locking block B2 and prevents rotation of the second locking block B2, and thus also prevents rotation of the input gear GR1, the main gear GR2, and the grounding shaft GSX. In this manner, when the locking assembly LA is positioned in its locked state, the grounding switch GS is restrained in its open (non-conductive) state. The locking member LP2 is shown as being linearly movable by the locking assembly LA in opposite first and second directions X1, X2, but those skilled in the art will recognize that the locking member LP2 may alternatively be movable along a non-linear path between its retracted and extended positions.

[0031] The key K is trapped or captured in the locking assembly LA when the locking assembly LA is in its unlocked condition and can be removed from the locking assembly LA only when the locking assembly LA is in its locked condition. This allows the key K to be used in a shared key interlocking system in which the same key K is used to operate both the first and second key interlocking devices to ensure that only one of the key interlocking devices is unlocked at any given time. Figure 4 The motor control center M is shown to include a key interlock device IX2 as described above and also include an isolator handle key interlock device HX, which includes a handle locking assembly HLA that, when locked, selectively locks the isolator handle IH in its "off" position to prevent the isolator handle IH from moving to the "on" position when locked. The handle key interlock device HX uses the same single key K as the grounding switch key interlock device IX2, and the key K is captured in the handle interlock device HX when it is unlocked, ensuring that the isolator handle IH moves to its "off" position and locks in its "off" position before the key K can be removed from the handle interlock device HX and inserted into the grounding switch key interlock device IX2 to unlock the grounding switch device GS, thereby allowing the grounding switch device to move to its conductive or "on" state.

[0032] Another advantage of the grounding switch interlocking system IK provided according to an embodiment of the present invention is that, unlike known systems, the grounding switch device GS is located on the load side of the main contactor CX, that is, electrically connected between the motor or other associated load LD powered by the motor control center M and the contactors X1 to X3 of the main contactor CX. Figure 5 As shown, the motor control center M is electrically positioned between the input power source P and the motor or other load LD. The isolating switch IS can be selectively operated to connect or disconnect the main contactor CX from the power source P. The grounding switch interlock device IX1 operably connects the isolating switch IS and the grounding switch device GS to each other via the interlock linkage device IXL as described above. The isolating switch IS is electrically connected to the main contactor CX, and the main contactor CX is electrically connected to the load LD on its downstream or output side. The grounding switch device GS is also located downstream or on the output side of the main contactor CX, so that the grounding switch contacts GC (GC1 to GC3) are electrically positioned between the main contactor CX and the load LD. When the grounding switch contacts GC of the grounding switch device GS are closed, a grounding path GP is connected between the load LD and the main contactor CX to safely ground or connect the main contactor CX and the load LD to the ground. This arrangement ensures that the load side of the main contactor CX is grounded when the grounding switch device GS is in its closed (conductive) state.

[0033] Figure 1 Another major advantage of embodiments of the present invention is illustrated. Here, it can be observed that the grounding switch contacts GC1 to GC32 are vertically aligned with the grounding terminals GT1 to GT3, respectively. In the case of a three-phase AC power supply, the three grounding terminals GT1 to GT3, respectively associated with the three phases of the power supply, are horizontally spaced apart from one another in a row. Similarly, the three grounding switch contacts GC1 to GC3 are horizontally spaced apart from one another in a row and vertically aligned with the grounding terminals GT1 to GT3, respectively, so that each grounding terminal GT1 to GT3 lies in a common vertical reference plane with respect to its associated grounding switch contact GC1 to GC3 for all operating positions of the grounding switch contacts GC1 to GC3. Thus, the three associated grounding terminal / grounding contact pairs GT1 / GC1, GT2 / GC2, and GT3 / GC3, respectively, lie in three parallel, spaced-apart vertical reference planes. This arrangement provides an operator with a simple and effective method of quickly and safely assessing the grounding status (grounded or ungrounded) of each of the grounding terminals GT1 to GT3 by visual inspection, because the operator will be able to visually determine whether each grounding terminal GT1 to GT3 is engaged by its associated grounding contact GC1 to GC3 by viewing the grounding switchgear GS from the front, such as through an access opening or window defined in the enclosure E. Figure 1 The first, second, and third grounding terminals GT1 to GT3 and the first, second, and third grounding contacts GC1 to GC3 are vertically aligned with the first, second, and third contactors X1 to X3 and the first, second, and third electrical phases, respectively, and are therefore visually associated with the first, second, and third contactors X1 to X3 and the first, second, and third electrical phases.

[0034] The physical position of the grounding switch device GS relative to the main contactor CX can be changed, for example, by: Figure 6 The grounding switchgear GS is positioned vertically above the main contactor CS as shown in the motor control center M' in FIG. Figure 1 It is shown positioned vertically below the main contactor CX (or the grounding switchgear GS may be positioned laterally adjacent to the main contactor CX). However, as described above, in all cases the grounding switchgear GS is electrically connected on the load or output side of the main contactor CX.

[0035] In the foregoing description, various embodiments have been described with reference to the accompanying drawings. However, it will be apparent that various modifications and changes may be made to the various embodiments described, and further embodiments may be implemented, without departing from the broader scope of the invention as set forth in the appended claims. Accordingly, the description and drawings are to be regarded as illustrative rather than restrictive.

Claims

1. A motor control center, comprising: an enclosure, the enclosure comprising a disconnector, a main contactor device and an earthing switch device; the disconnect switch being selectively manually operable between a connected state and a disconnected state, wherein the disconnect switch in the connected state is adapted to conduct power from an associated power source to the main contactor, and wherein the disconnect switch in the disconnected state interrupts conduction of power from the associated power source to the main contactor; the main contactor device being selectively operable between a conductive state and a non-conductive state, wherein when the main contactor device is in the conductive state of the main contactor, the main contactor is adapted to electrically connect the disconnect switch to the earthing switch device and the associated electrical load, and wherein when the main contactor device is in the non-conductive state of the main contactor device, the main contactor disconnects the disconnect switch from the earthing switch device and the associated electrical load; The grounding switch device is manually operable from an open ungrounded state in which the main contactor is electrically disconnected from a grounding path to a closed grounding state in which the main contactor is electrically connected to the grounding path; The motor control center also includes a first interlock device, which is operably connected between the isolation switch and the grounding switch device, wherein when the grounding switch device is in the grounded state, the first interlock device prevents the isolation switch from moving from the disconnected state to the connected state.

2. The motor control center according to claim 1, further comprising an isolating switch handle operably connected to the isolating switch and movable between an “off” position corresponding to the disconnected state of the isolating switch and an “on” position corresponding to the connected state of the isolating switch, wherein When the grounding switch device is positioned in the grounding state, the first interlock device prevents the disconnect switch handle from moving from the “off” position to the “on” position.

3. The motor control center according to claim 2, wherein: When the disconnect switch handle is in the “on” position, the first interlock device prevents the grounding switch device from moving from the ungrounded state to the grounded state.

4. The motor control center according to claim 3, wherein: The isolator switch handle is operably connected to the isolator switch through a mechanical isolator switch linkage, and wherein the first interlock device includes a locking plunger operably connected to the isolator switch handle through the isolator switch interlock linkage.

5. The motor control center of claim 4, wherein: When the isolating switch handle is in the "off" position of the isolating switch handle, the isolating switch interlock linkage moves the locking plunger to the retracted position; When the isolating switch handle is in the "on" position of the isolating switch handle, the isolating switch interlock linkage moves the locking plunger to the extended position; The grounding switch device comprises at least one movable grounding contact, wherein the at least one grounding contact moves between an open position in the ungrounded state and a closed position in the grounded state; and The locking plunger prevents the at least one ground contact from moving from the open position to the closed position when the locking plunger is in the extended position of the locking plunger.

6. The motor control center according to claim 5, wherein: The grounding switch device includes a first locking block, which is contacted by the locking plunger when the locking plunger moves from the retracted position toward the extended position when the at least one grounding contact is in the closed position of the at least one grounding contact and prevents the locking plunger from moving to the extended position of the locking plunger.

7. The motor control center according to claim 6, wherein: The first locking block prevents at least one ground contact from moving from its open position to its closed position when the locking plunger is in the extended position of the locking plunger.

8. The motor control center according to claim 7, wherein: The first locking block includes a first locking recess located in the first locking block, wherein the locking plunger is seated in the first locking recess when the locking plunger is in the extended position of the locking plunger and the at least one grounding contact is in the closed position of the at least one grounding contact.

9. The motor control center according to claim 8, wherein: the at least one grounding contact is connected to a rotatable grounding shaft electrically connected to the grounding path, the grounding switch device comprising a main gear connected to the grounding shaft and an output gear engaged with the main gear; wherein the first locking block is connected to the output gear in a non-rotatable manner so that the rotation of the grounding shaft changes the angular position of the first locking block; The first locking block is located in a selected angular position in which the first locking recess is aligned with the locking plunger when the ground shaft is rotated to a position corresponding to the closed position of the at least one ground contact.

10. The motor control center of claim 9, further comprising an input gear engaged with the main gear, wherein: The input gear is non-rotatably connected to a torque input head, and the torque input head can be selectively manually rotated to rotate the input gear, the main gear, and the output gear.

11. The motor control center of claim 10, further comprising a first key interlock device operable between a locked state and an unlocked state by a key, wherein: The first key interlock prevents the input gear of the grounding switch device from rotating when the first key interlock is in a locked state of the first key interlock.

12. The motor control center of claim 11, further comprising a second key interlock device operable between a locked state and an unlocked state by the key, wherein: When the second key interlock is in the locked state of the second key interlock, the second key interlock selectively prevents the isolating switch handle from moving, wherein: The key for operating the first key interlock and the second key interlock is a single common key; when one of the first key interlock and the second key interlock is in its locked state, the other of the first key interlock and the second key interlock is in its unlocked state; The key is captured in one of the first key interlock device and the second key interlock device in its unlocked state, so that the one of the first key interlock device and the second key interlock device must be moved to the locked state of the one before the other of the first key interlock device and the second key interlock device can be moved to the unlocked state of the other.

13. The motor control center of claim 12, further comprising a second locking block connected to the input gear in a non-rotatable manner, the first key interlock device comprising a locking member that engages the second locking block and prevents the second locking block from rotating when the locking member is in an extended position and the grounding switch device is in an open, ungrounded state of the grounding switch device.

14. The motor control center of claim 5, the grounding switch device being located on a load side of the main contactor.

15. The motor control center of claim 14, wherein: The grounding switch device comprises: a first grounding terminal, a second grounding terminal, and a third grounding terminal, the first grounding terminal, the second grounding terminal, and the third grounding terminal being electrically connected to respective first electrical phases, second electrical phases, and third electrical phases of the main contactor; The at least one movable grounding contact includes a first grounding contact, a second grounding contact and a third grounding contact, wherein the first grounding contact, the second grounding contact and the third grounding contact respectively contact the first grounding terminal, the second grounding terminal and the third grounding terminal when the first grounding contact, the second grounding contact and the third grounding contact are in their respective closed positions.

16. The motor control center of claim 15, wherein: The first ground terminal, the second ground terminal, and the third ground terminal are vertically aligned with the first ground contact, the second ground contact, and the third ground contact, respectively.

17. The motor control center of claim 16, wherein: The grounding switch device is located vertically above or vertically below the main contactor device; The main contactor device comprises a first contactor, a second contactor and a third contactor, wherein the first contactor, the second contactor and the third contactor are electrically connected to the first ground terminal, the second ground terminal and the third ground terminal, respectively; and The first ground terminal, the second ground terminal, and the third ground terminal are horizontally spaced apart from each other in a row such that the first ground terminal, the second ground terminal, and the third ground terminal are visually associated with the first contactor, the second contactor, and the third contactor, respectively.

18. An interlocking system for electrical equipment, the interlocking system comprising: an isolating switch selectively manually operable between a connected state and a disconnected state, wherein the isolating switch in the connected state is adapted to conduct electricity, and wherein the isolating switch in the disconnected state interrupts conduction of electricity; a handle operably connected to the isolating switch, the handle being movable between an “off” position corresponding to the disconnected state of the isolating switch and an “on” position corresponding to the connected state of the isolating switch; an earthing switch device that is manually operable from an open ungrounded state in which the isolating switch is electrically disconnected from an earthing path to a closed earthing state in which the isolating switch is electrically connected to the earthing path; an interlock plunger operably connected to the handle by an interlock linkage and movable to and between a retracted position corresponding to the "off" position of the handle and an extended position corresponding to the "on" position of the handle; The interlock plunger prevents the grounding switch device from moving from the open, ungrounded state to the closed, grounded state when the interlock plunger is in the extended position of the interlock plunger.

19. The interlock system of claim 18, wherein: The grounding switch device includes a first locking block that prevents the interlock plunger from moving from the retracted position to the extended position when the grounding switch device is in a closed grounding state of the grounding switch device.

20. The interlock system of claim 19, wherein: The first locking block includes a first recess that aligns with and receives the interlock plunger when the interlock plunger is in the extended position of the interlock plunger and the grounding switch device is in an open, ungrounded state of the grounding switch device.

Images