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4.3.3 Power connections from the isolation switch to the contactor shall be made using bus bar.
Connections from the contactor through the current transformers to the outgoing load terminals
shall be made using power cable.
4.3.4 The contactor shall be supplied with an optional mechanical latch with provisions for
manual or electrical trip.
4.3.5 The contactor shall be fully mechanically and electrically interlocked with the isolation
switch as described in the section on interlocking (4.5).
4.4 Power Fuses
4.4.1 Main current-limiting power fuses shall be provided for both motor starting (R rated) and
transformer feeder (E rated) applications.
4.4.2 Available fuse ratings for motor starting applications shall be Gould Type A051B2DAR0
rated 38R (630A), 5kV or A051B3DAR0 rated 57X (900A), 5kV.
4.4.3 Available fuse ratings for transformer feeder applications shall be Gould Type
A055C2D0R0-500E and 600E, and A055B3D0R0-750E and 900E, rated 5.5kV.
4.4.4 All power fuses shall employ bolt-in mounting.
4.4.5 The blown fuse indicators on the fuses shall be visible, through the viewing window, when
the medium voltage door is closed.
4.5 Interlocking
4.5.1 A mechanical interlock shall be provided between the vacuum contactor and the isolation
switch. The interlock shall prevent the isolation switch from being opened or closed unless the
main contacts of the contactor are opened.
4.5.2 The interlock described in 4.5.1 shall also operate in a manner such that it will prevent the
closing of the main contacts of the vacuum contactor unless the isolation switch is either fully
opened or fully closed.
4.5.3 An electrical interlock shall be provided as a backup to the mechanical interlock in 4.5.1.
This interlock shall switch off control power to the vacuum contactor at any switch position other
than fully opened or fully closed.
4.5.4 A mechanical interlock shall be provided between the isolation switch and the medium
voltage compartment door. This interlock shall prevent the door from being opened unless the
switch is in the fully open position.
4.5.5 The interlock described in 4.5.4 shall be capable of being circumvented in the event
emergency entrance to the controller is required. Circumventing the interlock shall require two
separate and distinct operations and shall require the use of a tool.
4.5.6 A mechanical interlock between the isolation switch and the medium voltage door shall be
provided to prevent the switch from being closed when the door is open. This interlock shall be
capable of being circumvented only by the use of a tool.