HC 75C
7-2
SECTION 7: POWER SECTION DESCRIPTION
Taps and Variable Transformer
To achieve a variable output from minimum to maximum, a system of taps and a motorized variable
transformer is employed. The tap selects the coarse range of the output and the variable transformer
controls the output from the ‘top’ of the previous tap to the maximum of the selected tap. The HC
Controller controls all of the taps and the motorized variable transformer. This method makes possible
the current hold and auto-jog functions.
A potentiometer is accessible on the front panel for varying the speed of the motorized variable
transformer.
All transformers and regulators are equipped with several thermocouples and a thermistor to monitor and
protect against an over-temperature condition. The output of the thermistor is fed back to the computer
controller in order to constantly monitor the temperature. In addition to these safeguards, the SCR
heatsink is forced-air cooled to provide lower operating temperature and a longer service life.
Metering
There is a precision current transformer employed in the high current section to measure the output
current. This transformer is placed directly around the output bus.
Output Stabs
The stabs are designed to be versatile and facilitate connection to a large variety of circuit breakers. They
are nickel plated for greater conductivity and a long service life.
The output stabs can be configured for parallel or series connection:
Parallel output connection is achieved by using the supplied stabs to short H1 to H2 for one
output connection and L1 to L2 for the other output connection.
Series connection is achieved by shorting L1 to H2 and connecting the breaker to H1 and L2. A
series connection link is available as an option.
Continuity
The continuity binding posts are located near the output stabs. These posts can be connected to an
unused pole of the breaker or an auxiliary contact. This allows the use of the Normally Closed or
Normally Open test modes by the test set.
If the continuity connections cannot be used (i.e. a single-phase breaker), the set must be operated in the
Current Latch mode.
CAUTION:
DO NOT CONNECT CONTINUITY TERMINALS TO ENERGIZED SOURCE.
DAMAGE TO CONTROLLER WILL OCCUR!
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