Abstract: An external racking device for remotely racking in and racking out an electrical circuit breaker from a cabinet. The racking device includes a motor head equipped with an electric motor, the electric motor being provided with a rotating shaft ended with an adaptor, and arranged to be coupled with a racking mechanism of an electrical circuit breaker, so that when driven in rotation, the shaft, depending of rotation, trigger either the racking in or the racking out of the circuit breaker from the cabinet. The external racking device further includes monitoring means intended to enable or to disable the operation of the electric motor depending on the status of a circuit breaker to be racked in or racked out from a cabinet.

Abstract: A low and medium voltage electrical enclosure comprising a supporting structure which defines an internal space delimited by walls forming one or more compartments housing one or more electrical apparatuses. At least one of said walls is provided with one or more venting openings that put into communication said internal space with the outside of said low voltage electrical enclosure and/or one of said compartments with a second compartment. The venting openings are provided with a cover closing a corresponding venting opening in a first—closed—operating condition at first predetermined temperatures and the enclosure is provided with an actuating device adapted to open said cover in a second—open—operating condition at second predetermined temperatures.

Abstract: An interlocking external actuator for accessing an electrical panel board having a circuit breaker inside a housing that is covered by an enclosure door, wherein the actuator includes a handle, a first shaft, a second shaft and an interlocking mechanism, wherein the second shaft engages the first shaft in a closed state of the door and thereby facilitates switching the circuit breaker to ON and OFF states by angularly displacing the handle, wherein the interlocking mechanism is biased to engage in pushing the door into a closed state, wherein the circuit breaker is switched from an ON state to an OFF state by displacing the handle from a first angular position to a second angular position, and wherein the interlocking mechanism is disengaged through displacement of the handle further to a third angular position and thereby allow opening of the door.

Abstract: A panelboard system includes a panelboard, a first circuit breaker in the panelboard, a second circuit breaker in the panelboard, and an interlock assembly. The interlock assembly includes: an interlock panel, a first protrusion on the interlock panel and positioned above the first circuit breaker, a second protrusion on the interlock panel and positioned above the second circuit breaker, and a toggle bracket pivotally connected to the interlock panel at a pivot member between the first and second protrusions. The toggle bracket includes a first arm extending from the pivot member toward the first circuit breaker and a second arm extending from the pivot member toward the second circuit breaker.

Abstract: The present disclosure relates to a circuit breaker equipped with an energy release device of a switching mechanism, and particularly, to a circuit breaker equipped with an energy release device that allows energy of a closing spring of a switching mechanism to be automatically discharged at the time of a withdrawal operation.

Abstract: An automatic actuator assembly including a passive actuator assembly and a detection assembly is operatively coupled to an arc reduction assembly. The passive actuator assembly is coupled to the arc reduction assembly and structured to move the arc reduction assembly between a disengaged, first configuration and an engaged, second configuration.

Abstract: A partition cover for a switchgear enclosure includes a main cover with a lip arranged along a first edge of the partition cover, a sliding cover with a second lip arranged along a second edge of the sliding cover, and a locking mechanism. The sliding cover is slidably supported on the main cover. The locking mechanism is fixed to the main cover and operably connected to the sliding cover, the locking mechanism is arranged to lock position of the sliding cover relative to the main cover to fix the partition cover within an interior of a switchgear enclosure. Switchgear enclosures and methods of emplacing and removing partition covers from within switchgear enclosures are also described.

Abstract: A switching device including a frame, a roll element, a control shaft, a drive system and a roll spring. The control shaft is adapted to control rotation of the roll element such that rotating the control shaft from an ON-position to an OFF-position carries out an opening event in which the roll element transfers from a first position to a second position. The drive system includes an actuator and an actuator spring. The drive system is adapted to rotate the roll element during the opening event to an intermediate position located between the first position and the second position. The roll spring is connected between the frame and the roll element, and is adapted to rotate the roll element to the second position during the opening event.

Abstract: A control attachment configured to provide power to a load is described. The control attachment may comprise a first plurality of contact elements configured to be coupled to a power adapter; a plurality of openings on a first surface and having a second plurality of contact elements configured to receive a power signal and a neutral signal, wherein the plurality of openings are adapted to receive prongs of a plug; and a transformer coupled to receive the power signal and generate a low voltage signal; wherein the second plurality of contact elements is coupled to the first plurality of contact elements.

Abstract: A lock assembly for a switch device of an electrical power distribution system includes a first lock and a second lock. The lock assembly also includes a connector arranged to inhibit movement of the first lock when the switch device is in a first position and inhibit movement of the second lock when the switch device is in a second position. The lock assembly further includes a guard coupled to at least one of the first lock and the second lock. The guard is positionable between a first position in which the guard allows access to an actuating mechanism of the switch device and a second position in which the guard inhibits access to the actuating mechanism. The guard is moveable between the first position and the second position when at least one of said first lock and said second lock is rotated.

Abstract: Disclosed herein is a drive unit for driving a tool mated with a tool receptacle in a device. The drive unit includes a tool carrying apparatus configured to carry the tool, and a proximity sensor cooperating with at least a portion of the tool carrying apparatus so as to detect movement of the tool carrying apparatus along a longitudinal axis thereof. A motor apparatus is configured to rotate the tool carrying apparatus. Control circuitry is configured to operate the motor in an engagement mode to rotate at least a portion of the tool carrying apparatus until the tool is rotationally aligned with the tool receptacle so as to permit insertion thereinto, based on the proximity sensor not detecting movement of the tool carrying apparatus a threshold distance along the longitudinal axis toward the tool receptacle.

Abstract: A safety device developed to promote more security and better efficiency in its use is provided to operate in the locking and actuation of electrical connectors positioned in extractable drawers for MCC cabinets, thereby setting a safety device capable of connecting or disconnecting the internal connectors, both principal and test connector, provided in the extractable drawer for MCC cabinet, the procedure is executed mechanically through an assembly of elements that interconnect two thin laminar plates and, these in turn, interconnected to each other, positioned inferiorly and of conformations corresponding to promote a perfect fit.

Abstract: A switching device including a switching unit with one or more electric poles having an insulating casing. The switching device is reversibly movable between an insertion position, at which said switching unit is electrically connected with an electric line, and a withdrawal position, at which said switching unit is electrically disconnected from said electric line. One or more actuating elements may be operatively coupleable with an actuating mechanism of a shutter device to operate one or more shutters of the shutter device during the movement of the switching device. The actuating elements may be fixed to the switching unit. At least one of the actuating elements includes a first mechanical connection with the insulating casing of at least one of the electric poles, and the insulating casing of at least one of the electric poles includes a second mechanical connection with at least one of the actuating elements.

Abstract: Motor control centers have units or buckets with one or more sliding shutters that controllably block access to a stab isolation port based on position of the operator disconnect handle using attached cams that slide the shutter right and left. A front panel of the unit or bucket may also be configured to pivot out about a long axis associated with a bottom long side thereof.

Abstract: An improved interruption apparatus includes a plurality of poles, with each of the poles including an actuator. In one embodiment, the actuator can be a fuse having a movable engagement element, and in another embodiment the actuator can be an electric coil that is operable to move a movable engagement element. The interruption apparatus has a single trip unit, and the engagement element of any actuator can actuate the trip unit to move all of the poles from a CLOSED state to an OPEN state.

Abstract: A switchgear unit includes an enclosure having a first compartment and a second compartment and a fuse assembly mounted on a wall that separates the first compartment and the second compartment, the fuse assembly comprising a fuse housing disposed in the second compartment and accessible from the first compartment via an opening in the wall. The fuse assembly may include a cover configured to separate a fuse in the fuse housing from the first compartment and that is removable to provide access to the fuse from the first compartment. The fuse assembly may further include a power input terminal supported by the fuse housing and accessible from the second compartment and a switch disposed in the first compartment and configured to electrically connect the power input terminal to the first fuse connection terminal.

Abstract: Withdrawable contactor trucks for a circuit breaker have a cradle with a motorized drive system comprising an electric motor in the cradle. The motorized drive system is configured to move the contactor truck in a controlled path between a withdrawn position and a levering-in position in a switchgear compartment.

Abstract: A manual charging apparatus for a vacuum interrupter, including a motor for charging a closing spring mounted on a vacuum interrupter; a charging shaft configured to rotate by a rotational force of the motor; and a manual charging handle coupled to one end of the charging shaft and configured to manually rotate the manual charging handle, wherein the manual charging handle includes an insertion part formed in an cylindrical shape and inserted into one end of the charging shaft; an extension part vertically bent from the insertion part and extended to increase a revolution torque; and a handle part vertically bent from the extension part and configured to apply a manual operation force, and wherein the insertion part includes a rotation restriction means configured to restrict a rotation in one direction.

Abstract: The present invention relates to a withdrawable arc eliminator having an interlock function, and more particularly, to a withdrawable arc eliminator having an interlock function capable of preventing insertion or withdrawal of an arc eliminator applied to an electrical panel, in a closed state of the arc eliminator.

Abstract: A first support member and a second support member are provided in a rotation support device and a worm gear is rotated in a state that the second support member is inserted in the first support member, whereby the worm gear is prevented from being shaken through the first support member and the second support member and heat transmission to a housing due to rotation of the worm gear to damage the housing is prevented.

Abstract: In the present disclosure, a link part is connected to a worm wheel rotated according to rotation of a worm gear and a movement member is connected to the link part, whereby a rotational motion of the worm wheel is changed to a translational motion in a horizontal direction through the link part and the movement member. Thus, although an indicator is positioned on an upper side of a handle insertion part, a position according to movement of a circuit breaker body may be easily indicated, while using a simple structure.

Abstract: A portable transmitting/receiving device, in particular in the form a remote control device for lifting and industrial devices, has a housing that has a receiving portion for accommodating an electronic controller and for mounting at least one operating element (such as a joystick, switch, regulator, or touchscreen with virtual operating elements). Additionally, the housing extends in the vertical direction from a lower-face base contour to an upper-face terminating contour and is perpendicularly delimited by a lateral contour. At least a substantial part of the housing is made of a molded housing part made of an elastomer, the molded housing part forming at least the upper-face terminating contour and the lateral contour. The molded housing part forms a basin that delimits the receiving area and that has a circumferential wall that is completely made of an elastomer and that has a closable opening.

Abstract: A coupling element is provided for an electric switching device wherein the coupling element includes a first switching contact for opening and closing an electric contact by a second switch contact. The coupling element has an oblong winding body having two ends that are opposite in the longitudinal direction of the longitudinal axis thereof, wherein the first switch contact is arranged on one end. The coupling element furthermore includes a rotation body through which the winding body extends and that is provided for coupling to a drive to carry out a rotation movement by the drive, wherein the rotation body includes two sides of which one faces one end (of the winding body and the other faces the other end of the winding body.

Abstract: A vacuum circuit breaker (VCB) assembly includes a single motor configured to rotate at least one rotor, a VCB having a breaking mechanism configured to control current flow through the VCB and a first electromagnetic clutch configured to selectively engage the at least one rotor with the breaking mechanism to charge the breaking mechanism. The VCB assembly also includes an undercarriage configured to support the VCB assembly and to move the VCB assembly from a first position to a second position and a second electromagnetic clutch configured to selectively engage the at least one rotor with the undercarriage to drive the undercarriage.

Abstract: The present disclosure relates to a circuit breaker positioning system and method including a circuit breaker casing and circuit breaker cell for connecting and disconnecting a circuit breaker to an external electrical circuit. The circuit breaker positioning system includes a motion system for receiving a rotational force from an external source and translating the rotational force into a displacement of the casing relative to the cell.

Abstract: A motor control center (MCC) unit includes a drawer having a space for accommodating a circuit breaker, a hinge bracket installed on one of left and right sides of the drawer, a base connected to the hinge bracket by a hinge shaft, and a display mechanism installation plate fastened to the base by a fastening member. Although a display mechanism or a display mechanism installation plates are different according to sizes or models of the MCC unit, a base and a hinge bracket may be commonly used.

Abstract: An assembly for a low voltage withdrawable switching device, comprising: a supporting frame into which/from which a switching unit of the withdrawable switching device can be inserted/withdrawn; a first connector placed at and protruding from a bottom portion of the supporting frame, which is adapted to be coupled with a second connector of the switching unit; and a shutter assembly. The shutter assembly comprises: an opening for allowing the coupling between the first and second connectors; a cover member which is adapted to be moved from a cover position to an open position so as to make the opening accessible for the coupling between the first and second connectors. The cover member is adapted to be moved from the cover position to the open position by the first connector. The shutter assembly is operatively mounted movable into the supporting frame.

Abstract: A removable electrical power cell including an incoming electrical source connector with a circuit interrupting device and an electrically isolated outgoing electrical load connector, an electro-mechanical switching assembly connected to a movable disconnect switch to move the disconnect switch between an open and grounded position and a closed and energized position and a controller to provide an input signal for controlling the operation of the electro-mechanical switching assembly to control an operation of the removable electrical power cell. The electro-mechanical switching assembly includes a rack and pinion switching assembly and a lockout limit switch to control operation of the automatic power switching assembly. The electro-mechanical switching assembly including a motor driven switching assembly to automatically open and close the high voltage power isolation switch based on an incoming signal.

Abstract: An electrical switching apparatus assembly is for a switchgear system. The switchgear system includes a number of circuit stabs and an enclosure having a number of compartments. The electrical switching apparatus assembly includes an electrical switching apparatus having a number of terminals and a mounting assembly, the terminals being structured to be mechanically coupled and electrically connected to the circuit stabs, the mounting assembly comprising a mounting member coupled to the terminals; and a maintaining assembly comprising a plate member and a maintaining member, the plate member being coupled to the mounting member, the maintaining member being coupled to the plate member and structured to engage the enclosure. Responsive to an arc fault event, the maintaining assembly is structured to move between FIRST and SECOND positions. When the maintaining assembly moves from the FIRST position to the SECOND position, the plate member moves away from the terminals.

Abstract: An improved interruption apparatus includes a plurality of poles, with each of the poles including an actuator. In one embodiment, the actuator can be a fuse having a movable engagement element, and in another embodiment the actuator can be an electric coil that is operable to move a movable engagement element. The interruption apparatus has a single trip unit, and the engagement element of any actuator can actuate the trip unit to move all of the poles from a CLOSED state to an OPEN state.

Abstract: Methods, systems, devices for a motorized isolation switch including a switch enclosure with a set of fixed insulated floating input line connectors and output load connectors movably fixed to the rear panel, a removable contactor bucket insertable into the isolation switch enclosure with mating movable insulated line terminals and load terminals and a set of insulated circuit interrupters, a motorized rack and pinion assembly connected to a base of the switch enclosure, coupled for moving a contactor pan connectable to the contactor bucket along a stationary rack gear along the base of the switch enclosure between and switch open position and a switch closed position, an insulating grounding block with ground connectors, the contactor bucket with corresponding movable ground terminals to mate with the insulated ground connectors in the switch open position, and ancillary controls for communicating with remotely located controls to electrically control the operation.

Abstract: A portable motorized device for remotely inserting or removing (racking) draw-out power circuit breakers. Many different designs of draw-out circuit breakers may be connected or disconnected from an energized bus by a human operator cranking a jack screw mechanism that is part of the breaker. The device herein described provides a portable, motorized device that can be hand-carried to the work location and affixed to the circuit breaker without the need of any modification to the breaker or its enclosure. The torque that is required to operate the breaker's racking mechanism is provided by an electrically powered gear motor. Attached to the output shaft of the gear motor is a socket that engages the circuit breaker racking screw. Anti-torque is provided by a portion of the portable racking device that engages the racking screw support frame.

Abstract: A method for evaluating mechanical performance of a switchgear device having at least one pole which includes a pair of contacts movable between open and closed positions, a support arm of a first contact, a support arm drive including a rotary pole shaft and a rod pivotably coupling the drive to the support, an energy storage system for moving the arm to close the contacts, and a toggle device with a trip latch, the method including measuring the angle of rotation of the pole shaft during contact closing, deriving specific values by measuring the angle of rotation, comparing the values with an initial reference value, identifying wear performances of the drive by comparing the specific values with the reference value, determining on a variation curve of the angle of rotation versus time, a first specific time to reach a first inflection point when the pole shaft reaches a maximum speed of rotation, and a second time to reach a point on the curve at a theoretical final angle of rotation when the contacts are

Abstract: A portable racking tool for the installation and removal of electrical equipment, such as circuit breakers, is disclosed herein. Also disclosed is a method of using the portable racking tool. The portable racking tool can be lightweight and rugged for providing electrically operated controlled installation and removal of electrical equipment by an operator from a remote location using a coupling for engagement with the electrical equipment.

Abstract: A restraint assembly is for a switchgear system. The switchgear system includes an enclosure having a number of compartments and a number of electrical apparatus, such as for example, circuit breakers, movable into and out of the compartments. The restraint assembly includes at least one latch assembly comprising a mounting member, a latch pivotably coupled to the mounting member, and a number of biasing elements biasing the latch. The latch moves between a latched position corresponding to the latch locking an electrical apparatus within a corresponding compartment, and an unlatched position corresponding to the electrical apparatus being movable with respect to the compartment. The biasing elements bias the latch toward the latched position.

Abstract: The invention has an object to provide an operating device or vacuum switch which permits reduction in the overall height of the operating device and improves installation convenience. In order to solve the above problem, an operating device according to the present invention is characterized by including an electromagnet 14 located in a case 10 and fixed to the case 10 through a fixing part, a capacitor 16 located at an end in the case 10, a control board 18 located opposite to the capacitor 16 across the electromagnet 14, an auxiliary contact 34 located above the capacitor 16, a movable part to move by a magnetic force generated from the electromagnet 14, and a power transmission section to operate in conjunction with movement of the movable part. The capacitor 16 and the auxiliary contact 34 are located at heights not exceeding the height of the fixing part for fixing the electromagnet 14.

Abstract: A linear actuating earthing switch configuration that moves movable contacts using linear motion in a single axis. The earthing switch includes a frame with a rail on a slide wall. A sliding carriage slides on the rail in a linear direction, the sliding carriage including a plurality of movable contacts. A stored energy element provides a linear expansion force between the frame and the sliding carriage when the earthing switch is in an open position.

Abstract: A method for evaluating mechanical performance of a switchgear device having at least one pole which includes a pair of contacts movable between open and closed positions, a support arm of a first contact, a support arm drive including a rotary pole shaft and a rod pivotably coupling the drive to the support, an energy storage system for moving the arm to close the contacts, and a toggle device with a trip latch, the method including measuring the angle of rotation of the pole shaft during contact closing, deriving specific values by measuring the angle of rotation, comparing the values with an initial reference value, identifying wear performances of the drive by comparing the specific values with the reference value, determining first and second specific values on a variation curve of the angle of rotation, calculating the angular difference between maximum and final angles of rotation; and identifying a latching state of the toggle device as a function of the angular difference.

Abstract: An interlock structure is coupled between actuating structure and a travel adjuster of a circuit breaker. The interlock structure includes a body having a bore therein. An engaging member has a portion sized to be received by the bore and the engaging member is coupled with the travel adjuster for movement therewith. A slide member is movable with respect to the body between operative and inoperative positions. Linkage structure is coupled to the slide member for moving the slide member and is also coupled to the actuating structure such that upon movement of the actuating structure, the linkage structure moves the slide member to the operative position so that the slide member blocks at least a portion of the bore to prevent the engaging member from entering the bore and thus prevents the travel adjuster from moving in a certain direction to allow the closure of the circuit breaker contacts.

Abstract: A connection system for connecting electrical devices to busses within a switchgear cabinet includes an independently movable shutter that slides along a bus bar, the shutter covering access to the bus bar in a disconnected position and allowing access in a connected position. The bus bar has an insulator cap covering its free end. The shutter is mounted to a spring-biased support. The shutter has an opening through which the bus bar passes. The shutter slides along the bus bar backwardly away from the insulator cap, in the connected position. The shutter slides forwardly along the bus bar toward the insulator cap, in the disconnected position. The insulator cap fits closely within the opening in the shutter to prevent access to the bus bar when in the disconnected position. The shutter can fit within arc attenuating phase barriers surrounding each bus bar and be constructed to be arc resistant.

Abstract: A protective shutter device for exposing and preventing access to electrical contacts of a switchgear. The device includes a linkage assembly coupled to the housing, the linkage assembly including a first and a second drive arm. A guide assembly is coupled to the housing, and includes a first end, a second end, and a body connecting the ends. The device further includes a first shutter coupled to the first drive arm and the body of the guide assembly. The first shutter selectively moves along the body. A second shutter is coupled to the second drive arm and the guide assembly body, the second shutter including a lower and an upper plate. The lower plate is coupled to the upper plate, wherein the plates selectively move along the body to a first position to expose the electrical contacts, and to a second position to prevent access to the electrical contacts.

Abstract: An electrical device removal tool, such as for circuit breakers, that is lightweight, portable, and rugged for providing electrically operated controlled insertion and removal of electrical equipment by an operator from a remote location using a coupling device for engagement with the electrical equipment housing.

Abstract: A guide assembly for a switchgear assembly is provided. The guide assembly includes an elongated support member and a passage. The support member is coupled to and extends from a housing assembly rear sidewall. The support member extends in the circuit breaker assembly direction of travel. The passage is disposed on the circuit breaker assembly base and also extends in the circuit breaker assembly direction of travel. The support member is substantially aligned with the passage. In this configuration, as the circuit breaker assembly moves between a withdrawn position and an installed position, the support member moves between a first position, wherein the support member is not disposed in the passage, and a second position, wherein the support member is partially disposed in the passage. When the support member is in the second position, the support member bears a portion of the weight of the circuit breaker assembly base.

Abstract: A system having electrical equipment integrated on a structure is provided. The system includes at least one electrical equipment located at a spaced apart relationship and mounted on at least one structure. A method is provided for isolation of electrical equipment. The method includes opening and closing a contact by engaging or disengaging one or more terminals of the electrical equipment correspondingly with a supply line or a distribution line by a mechanism for isolation. The mechanism can be a handle or a moving mechanism which is associated with a movement in a vertical direction or horizontal direction or with a movement that provides isolation.

Abstract: A circuit interconnect device racking apparatus is disclosed. The circuit interconnect device racking apparatus has a body adapted to couple to a circuit interconnect device, one or more frame connectors coupled to the body, a racking lever coupled to the body by a lever pivot, the racking lever having a cam mechanism component, and one or more bus connectors configured to connect to or disconnect from one or more bus bars responsive to rotation of the racking lever. Circuit interconnect device racking assemblies having the circuit interconnect device racking apparatus and methods of connecting circuit interconnect devices to one or more bus bars are disclosed, as are other aspects.

Abstract: A linear actuating earthing switch configuration that moves movable contacts using linear motion in a single axis. The earthing switch includes a frame with a rail on a slide wall. A sliding carriage slides on the rail in a linear direction, the sliding carriage including a plurality of movable contacts. A stored energy element provides a linear expansion force between the frame and the sliding carriage when the earthing switch is in an open position.

Abstract: A shutter device is provided for a bypass isolation automatic transfer switch. The shutter device comprises a frame and a shutter that is movably supported by the frame and that is configured to selectively cover and uncover conductors. At least one cam is movably supported by the frame and at least one shutter lever is interposed between the shutter and the at least one cam. The shutter lever is configured to move the shutter in response to movement of the cam.

Abstract: A disconnect mechanism, an electrical component assembly including the disconnect mechanism, and an electrical circuit protector in turn including the electrical component assembly. The disconnect mechanism includes a carriage, as well as a switch actuator connected to the carriage for moving the carriage between a switch-closed position and a switch-open position. A contactor is mounted to the carriage so as to move with the carriage, the contactor including first and second contactor terminals and providing selective electrical connection between the contactor terminals. A movable disconnect switch contact is connected to the first contactor terminal, and is movable with the carriage and the contactor. A fixed disconnect switch contact is positioned for selective engagement with the movable disconnect switch contact as the carriage moves to the switch-closed position.

Abstract: A linear actuating earthing switch configuration that moves movable contacts using linear motion in a single axis. The earthing switch includes a frame with a rail on a slide wall. A sliding carriage slides on the rail in a linear direction, the sliding carriage including a plurality of movable contacts. A spring surrounding a linear shaft provides a linear expansion force between the frame and the sliding carriage when the earthing switch is in an open position.

Abstract: A drawout unit that disconnects both polarities of DC current from a DC source, when all poles are used for one of the polarities leaving no pole available to disconnect the other polarity. The drawout unit includes a disconnect device having a four-pole switch, and all four poles are series-connected to the positive (ungrounded) polarity. A separate drawout module with its own housing is connected to the negative (grounded) polarity, and together, the disconnect device and the drawout module are positioned in a cradle with a racking mechanism for racking both the device and the module in and out of the cradle simultaneously, thereby obtaining total isolation of both polarities. In this configuration, the installer has the option to ground the negative polarity, while leaving the positive polarity ungrounded. The drawout module has a through bar conductor that passes the negative polarity of the DC current through the drawout unit.