THC trouble?

[Red Earth]

While running a job, the THC quit.

I could manually switch the THC off in Mach 3 and run the job, but with it on the torch will run to the part set the height, fire and not move.

Any Ideas?

[Torchhead]

You have lost the Arc Good signal. It is operating correctly because it is waiting for an indication there is a valid arc before releasing motion. The is a green LED on the front that indicates and ARC (Arc good). It has to come on and stay on for the software to release motion.

[Red Earth]

Both ARC Good lights, on the THC and the MAch 3 screens are on indicating an arc.

[Red Earth]

Back in the shop today....

The CP light is on, Arc light and fault light does not come on but the torch light does.

In mach 3 the torch active is lit when the cutter is on or off. The arc light does not turn on either.

I thought it was odd for it just to quit in the middle of a job. Should we recalibrate the arc good trip points?

[Torchhead]

If you are using the external CT transfomer to sense current:

Check wiring and connections back to THC Sensor card for Arc Okay
Check to make sure resistor across the CT has not come loose
Check resistor value with one side disconnected from CT terminals = 15 ohms
Check resistance with resistor back on the CT across the leads. Should be (much) lower ohms than 15.

With AC voltmeter across the two leads fire torch on metal manually. Voltage should be min 7VAC up to 24VAC.

If voltage is correct and getting to Sensor terminals then possibly you have a problem on the card itself. You can pull the card and use a source of 9 to 20 VDC (or ac) into the ARC Okay terminals on the card (everything else disconnected). You should hear a relay click. If it does not, adjust the VR1 sensitivity pot and see if the relay turns on. If it does then the problem is between the card and the rear connector of the THC unit.

[Red Earth]

Thanks TH...
The wiring was all good. The resistor checked at 16 ohms.

The volts across the CT read 4.49 volts. I had 5 wraps around as well. I used aluminum wire, changed it to 6ga. copper, still no difference. With 4 wraps it read 4.39. It has been working for a few months with this voltage.

I replaced the CT, still no change.

This is in a Hypertherm 600.


Would running both hot leads through the CT help?