Hypertherm HT4001 Plasma Arc Cutting System - Manual (Page 148)

MAINTENANCE
9/9/97
6-22
HT4001
Instruction Manual
Chopper Module Test Procedure
Note: Take voltages with a digital multimeter (DVM) capable of storing min. and max. readings.
1. Turn all power to the HT4001 system OFF.
Disconnect two terminals on line filter to disable the high frequency transformer T1. See Figure 7-8 for location
of T1.
Note: RHF console doors must be re-shut before attempting to start system.
2. Remove large fuses F1, F2, F3 and F4. Check to see if fuse(s) is (are) open.
3. Place the positive lead of the DVM to the + side of the bridge and the negative lead to the – side of the bridge.
See Figure 6-3. Note that actual connection points are hidden by cap support bracket in Figure 6-3.
4. Turn power to the HT4001 ON, and start system up. After the START command has been given, check voltage.
The input to the chopper at these points should be about +360 VDC. If the input is OK and corresponding fuse
F1, F2, F3 or F4 is blown, replace the chopper module. If there is no +360 VDC input, check the 3
φ
AC input to
the chopper. Also, check contactors (CON1, CON2), contacts, and connections and associated wiring to the
contactor. See Routine Maintenance – Power Supplies in this section to inspect and replace contacts. Repair
and/or replace defective component(s) if necessary.
5. If voltage from above step is +360 VDC and corresponding fuse is not blown, check output of choppers.
CH1 • Place the positive lead of the DVM at point (+) WORK on the chopper module (wire #48A) and
negative lead at point (-) TORCH (wire #39A). See Figure 6-3.
• Turn the system on and press the START command. After the START command has been given,
check the voltage. If the output from these points is +360 VDC, chopper is OK.
CH2 • To check the output of CH2, repeat the above procedure for CH1 but put the positive lead of the DVM
at wire #48B and the negative lead at wire #39B.
Before checking output of choppers CH3 and CH4, switch connector PL3.6 with PL3.9 and also switch
connector PL3.5 with PL3.7 on analog PCB3. See Figure 6-3A.
CH3: To check the output of CH3, repeat the above procedure for CH1 but put the positive lead of the DVM at
wire #48C and the negative lead at wire #39C.
CH4: To check output of CH4, repeat the above procedure for CH1 but put the positive lead of the DVM at
wire #48D and the negative lead at wire #39D.
WARNING
SHOCK HAZARD: Use extreme care when working near the chopper modules. The large electrolytic
capacitor(s) (blue-cased cylinder(s)) store large amounts of energy in the form of electric voltage. Even
if the power is off, dangerous voltages exist at the capacitor terminals, on the chopper, and the diode
heatsinks. Never discharge the capacitor(s) with a screwdriver or other implement … explosion,
property damage and/or personal injury will result.