HC 75C
7-1
SECTION 7: POWER SECTION DESCRIPTION
Fuses and Circuit Breakers
The single phase input power enters the regulator through CON202 and CON203 and is immediately
connected to CB201. Circuit breaker CB201 protects the main power section and is equipped with an
under-voltage release coil. The under-voltage release coil is wired so that if an interlock opens, the main
circuit breaker will open and disable the power section.
Circuit breaker CB202 protects the output of the variable transformer, T202A/B, and the input to
transformer Primary #1 of the main transformer T301.
Fuses F201 and F202 provide control power transformer protection. Fuse F203 protects the 120 V
control circuits and F204 protects the vernier motor controller.
Interlock Circuit
The interlock circuit is a safety mechanism that prevents the high power section from operating under
unsafe conditions. The following conditions must exist to close the interlock:
1. Control power must be on.
2. The computer controller must be on, out of reset, and running the HC software. If the controller is
displaying INTERLOCK or OVERTEMP, the interlock will not close.
3. CB202 must be in the ON position.
4. The Emergency Off mushroom switch must not be pressed. (Ensure that it is pulled out.)
After the interlock circuit is closed, the panel INTLK light will go out and allow the main circuit breaker
CB201 to be reset.
Triggering
A SCR Trigger board, PCB201, turns the high current output ON when signaled by the HC Controller.
The trigger board receives its command from the HC Controller via an I/O interface PC board, PCB202.
The HC Controller precisely controls the phase angle and duration of the output waveform.
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