Over Voltage Alarm?

[UBRacing]

I have had this 95 vf-0 for a year. Now all of a sudden im getting a over voltage alarm (119).
I'm running a phase convertor .

Would this be something with the machine itself or is it my incoming power supply?.

Any places to start to look ?. Im going to get a electricion to check my incoming voltage again.

Thanks

[cjmerlincnc]

Measure the voltage between phases if there is one that is way-out then you'll probably find a capacitor is faulty in the phase converter.

[Geof]

You can get an overvoltage alarm whether the machine is running or not from the incoming power being too high; this pushes the DC voltage too high.

If your incoming phases are out of balance you may get an overvoltage alarm or you may get a phase loss alarm.

If the overvoltage alarm occurs when the spindle is stopping it is probably because the Regen resistor is not coming into action. Braking the spindle pumps up the DC voltage and when it reaches a particular point a circuit closes to dump energy into the Regen resistor and stops the voltage going any higher. If the voltage sensing circuit is faulty then the circuit never closes and if the resistor is burnt out then it never dumps the energy.

Check for continuity through the Regen resistor the resistance is quite low, maybe around 8 ohms. The value has been quoted in some posts but I cannot remember it exactly.

[UBRacing]

we tested the power going in to the phase convertor and at the machine. It all tested out good.

Geof were do I find the regen resistor on the machine?

I also seen were you post this before "

This sounds like an open circuit on the braking resistor. That is the thing inside the cage on top of the machine that gets hot.

When the spindle slows down or stops it does it by rgenerative braking and the controller dumps power onto the DC buss. When the DC buss voltage goes above a certain level the braking resistor, also called the regen resistor is brought into the circuit to bleed off excess voltage. I think there is a relay somewhere that is supposed to close.

If, for some reason, the circuit to the regen resistor does not close the bud voltage goes up and triggers and overvoltage alarm."

Can you whatch the dc buss to see if the regen resistor maybe faulty?

[Geof]

Originally Posted by UBRacing .....Geof were do I find the regen resistor on the machine? ..... Can you whatch the dc buss to see if the regen resistor maybe faulty?

The resistor is the thing on top of the control cabinet in a metal screen.

You should be able to go to the DIAGNOSTICS screen (Push the PARAM key twice) and then page down and find DC BUSS VOLTAGE. I don't have any 1995 machines so this may not work.

When(If) you find the DC VOLTAGE try starting and stopping the spindle while watching it. You should see it drop on start and go up on stop. Do this for various speeds and see if you can trigger the overvoltage alarm. On my machines the DC voltage peaks out at about 380 when the spindle is topping from a high speed but I have no idea if this will be the case with yours.

[UBRacing]

I watched the DC BUSS it reads normally around 170-177 with the spindle running. When the over voltage alarm goes on it reads around 181-182.

Do you think it could be the regen resistor?

[Haas__man]

ok,
I would suggest that your overvoltage alarm is not caused by the spindle or regen. Your machine has brushed axis motors and I would say that one of these motors could well be causing your problem. Here are some tests for you to try, you will need a multi meter:
Turn off the machine
leave the machine turned off for at least 10 minutes before next step
Look in the electrical cabinet
look at left hand side of cabinet half way down
you should see 4 drive card units (all four PCBs should be checked)
There will be a black and red wire plugged into the top of the pcb
and a black and white cable just below the middle of the PCB
Remove the black and white wires from the PCB (remember which way round they are)
Now you need to check resistance from the black wire to an earth point
This reading should be higher than 500k ohms (prefferably open circuit)
re attatch the black and white wires.
Now check the other three PCBs.
If any of the readings are less than 500 kohms then that axis is your problem. It would mean that the motor has a build up of carbon inside and would definately give the symptoms that you describe.
If all motors check out ok then i would suggest the problem is with your servo distribution PCB. This PCB is situated just to the right of the four PCBs that i have already described (it has two big blue capacitors on it.
Hope this helps