Hypertherm PAC500 Water Injection Plasma Cutting System - Manual (Page 49)

5-8 PAC500 Instruction Manual
4
MAINTENANCE
j. Depress the STOP button, then the START button to restart the test cycle.
k. After five seconds of preflow, a steady spark discharge should be observed inside the nozzle bore.
Do not touch the torch. This discharge has a 1.7 second duration. It is terminated by 2TR. To observe
the discharge again it is necessary to depress the STOP button and then the START button.
If there is no discharge or it is erratic, check the leads from the torch to the console for tightness. Check
the spark gap setting for correct electrode spacing (.020 in.).
2. Power supply contactor not activating.
a. With the TEST/RUN Switch in RUN, the power supply should come on with the GREEN light. Contactor
closure may be verified by reference to the Voltmeter on the power supply which should indicate open
circuit voltage upon contactor closure.
3. Blown fuse(s) in the power supply disconnect box.
4. Burned out water cooled resistor, R2 (figure 7, page 5-17).
a. Resistance measured between terminals 31 and 32 should be approximately 3 ohms.
D. Pilot arc strikes, but will not transfer
1. Excessive torch-to-work distance (see Section 4 Applications Data).
2. Poor ground connection to workpiece.
a. This problem may be caused by a buildup of heavily oxidized metal on the slats of the cutting table.
Connect the ground lead directly to the workpiece. If this cures the problem, clean or replace the support
slats.
3. Heavy layer of scale or primer on the workpiece.
E. Torch dives into workpiece during cutting, or torch height drifts.
1. Defective Voltage Divider. The Voltage Divider reduces the arc voltage by a ratio of 25:1. It may be
checked by energizing the Plasma Power Supply and measuring the Divider output. At the power supply
open circuit voltage of 400VDC, the Divider output should be approximately 16VDC. To take the Divider
output measurement, perform the following:
a. Disable High Voltage Transformer (HVT) by disconnecting its primary wires. See figure 6 for location of
HVT.
b. Place a voltmeter across the Signal and Ground terminals of the Voltage Divider.
c. Place the CONTROL switch to MAN position,the ARC switch to AUTO position, and the Plasma
TEST/RUN switch to the RUN position.
d. Depress the START switch and note the Voltage Divider output.
e. Press the STOP switch to de-energize the main contactor after you have taken the Divider measurement.