Basic Installation and Operation Guide
JK 400 Series Fixed Controllers
TOSHIBA
18
D. Control Power/Potential Transformers
A control power transformer (
Fig. 2
8a) is fix-mounted on the left
side of the controller compartment. Power is supplied to the fused
primary of the control power transformer from the load side of the
main power fuses.
Optionally, a second transformer (Fig. 2
8b), normally used as an
instrument transformer, can be mounted in the compartment.
When this option is supplied, the two transformers are normally
connected in an open-delta arrangement.
Another option sometimes supplied is a second control power
transformer connected in parallel with the first to increase the
available KVA capacity.
Both the control and optional potential transformers are used to
supply power to the low voltage circuits of the controller. This
includes power for the vacuum contactor operating coil and
instrumentation. Reference the equipment’s schematic drawing(s)
for details.
Fig. 28a Control Power Transformer
An electrical interlock is provided to ensure that all load is
disconnected from the control power transformer secondary
winding before the power isolation switch can be opened or closed.
Fig. 28b Optional 2
nd
Transformer
