Hypertherm HT4400 HySpeed Plasma Arc Cutting System - Manual (Page 123)

MAINTENANCE
5-32 HT4400 Instruction Manual
3
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 HT4400 system OFF.
Disconnect 2 terminals on line filter FL1 in the ignition console to disable the solid-state ignition.
2. Remove large fuses F1, F2, F3 and F4. Check to see if any fuse is 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 on the facing page. Note that actual connection points are hidden by capacitor support
bracket in figure.
4. Turn power to the HT4400 ON, and start up system. 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-phase AC input to the chopper. Also, check contactors (CON1, CON2), contacts, and
connections and associated wiring to the contactor. Repair or replace any defective components.
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 the figure on following page.
• Turn the system on and give 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.
• An alternate method of testing is to keep fuses F1-F4 in place and take voltage as above. A low
voltage reading with this method could mean a shorted torch.
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 on the following page.
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 any capacitor with a screwdriver or other implement...explosion,
property damage and/or personal injury will result.