MPE DP SERIES II, Operating And Service Manual

Page: 125 / 145

7.3.2 Driver Board
The driver board contains two potentiometers which are used to set under voltage and over current
protection in the polyphase chopper circuitry. These potentiometer do not normally need
adjustment in the field.
7.3.2.1 Over Current Protection
Over current protection should only be calibrated after consultation with the factory.
Gross misadjustment can cause chopper and inverter failure.
Place a dc voltmeter between test point TP6 (positive) and test point TP7 (negative). With only
the control power applied, adjust potentiometer P1 to 6.00 V.
7.3.2.2 Under Voltage Protection
Under voltage protection should only be calibrated after consultation with the factory.
Gross misadjustment can cause chopper and inverter failure.
Connect the power supply to an adjustable ac source and connect an ac voltmeter to monitor the
voltage applied to the input terminals. Tests can be performed under no load conditions. Set the
ac source to rated voltage. Turn the control power, press the start switch, and a adust the output
voltage to 10% full scale output. Decrease the ac source to a value between 75% to 82% of rated
voltage. Adjust potentiometer P2 until the output drops to zero; the transition will be abrupt.
Decrease the ac source to a value between 72% to 79% of rated voltage. The main contactor
should turn off.
112