Hobart 6T28-600CL Operation And Maintenance Manual page 49

OM-2244 / Operation and Maintenance Manual
DCS-600/ Series 500082 / Solid State Transformer-Rectifiers
Calibration Procedure
(1) Connect the output cable to the load bank.
(2) Connect a voltmeter to the output.
Turn the power switch on. The amber "Power On" light should be on.
(3)
(4) Set the SCR gate balance
a) Connect the oscilloscope probe to the heat sink and the oscilloscope ground to the braid of the
heat sink fly-back diode (CR 7).
b) Verify output pulses for the six SCRs.
c) Balance the levels with R9 and R10.
Close the output contactor. Make sure the green "Contactor Closed" light turns on.
(5)
(6) Turn the GPU off.
(7) Adjust the offset null
a) Connect another voltmeter to TP14 (positive) and TP15 (negative).
b) Turn on the GPU and close the output contactor.
c) The test point voltage should be 0.000 ± 0.005 VDC.
d) Adjust R38 (offset null adjust) for the proper reading.
(8) Adjust the voltage reference
a) Move the positive voltmeter lead to TP19.
b) The voltage should be -5.00 ± 0.010 VDC.
c) Adjust R101 (reference adjust) for the proper reading.
(9) Check the over-voltage adjustment
When an over-voltage occurs, the output contactor should open and the red "Overload" light should
turn on.
a) Turn the "Starting current" knob to the maximum setting.
b) Turn R109 (28 volt adjust) all the way counterclockwise. The output voltage will drop to around
22 volts.
c) Jumper a 3.3 k resistor across R111 (next to R109). The output voltage will increase to about
30 volts.
d) Use R109 to raise the output voltage until the over-voltage fault trips. The output voltage must be
between 31.0 and 31.8 VDC at the trip point.
e) Adjust R37 (over voltage adjust – control very touchy) for proper trip point.
f) Remove the 3.3 k jumper resistor and reset output voltage for 28.50 to 28.60 VDC.
December 15, 2014 Chapter 2-2
Page 7