Basic Installation and Operation Guide
JK Series 720 Controllers
TOSHIBA
Controller Compartment
A. Isolation Switch
Power is switched on and off to the controller by a fix-mounted,
externally-operated, three-pole, non-load break, isolation
switch (Fig. 23). When the switch is in the off position, incoming
power is isolated from the controller compartment interior by
an automatic shutter. For additional safety, the load terminals
of the switch are automatically grounded when the switch is off.
Three bolted-in current-limiting power fuses provide primary
short-circuit protection for the controller and load circuit. These
fuses are connected between the isolation switch and the
vacuum contactor. The vacuum contactor load terminals are
cabled through three metering current transformers (plus a
ground sensor, if supplied) to the outgoing load terminals.
Current transformers furnished are of the window (donut) type.
Fig. 23 Isolation Switch
The isolation switch is mechanically interlocked with the vacuum contactor and the compartment door. Details of the
interlocking are discussed in Section F.
The position of the isolation switch blades can be observed through a
window in the medium voltage compartment door. Thus, it is possible to
have visual evidence that the power source is isolated before entering the
medium voltage compartment. The switch is also provided with lock-out
provisions (Fig. 24).
The isolation switch has a maximum interrupting capacity of 0.4 amperes.
Do not connect additional load to the isolation
switch.
Fig. 24 Isolation Switch Lockout
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