Need Help!- Input fuses blowing on 6T spindle drive

[Jerry Shorter]

Ikegai FX-15 with a 6T control keeps blowing the input fuses on the DC spindle drive unit. I have checked all of the SCR's with a DVM and can find none of them shorted. I replaced the motor with one recently rebuilt and still the fuses blow also the black 1.3 amp fuses on the control board blow. Could it be possible that the control board is turning on the SCR's out of phase, causing F1,F2, or F3 to blow, Sometimes 2 of the 3 will blow. anyway I,m stumped. I called tech support at Fanuc but they were not a lot of help. Thanks in advance.

Jerry

[alexfanuc]

Did you check the fan in the spindle unit?
Also, check the fan at the motor although you say you´ve got another motor.
regards,
Alexfanuc

[Al_The_Man]

Try with the motor disconnected, if the fuses still blow the problem is in the drive.
Unless it is random blowing when running, then it is hard to test this way.
Al.

[Jerry Shorter]

Alex, Yes the fan is fine. I did have a problem with the fan at one time but it was blowing F4

Al, I tried disconnecting the motor, the fuses didn't blow but there was an immediate speed alarm so I am not sure they even had time to blow before the unit shut down. The fuses blow immediately upon the issue of a speed command when the motor is hooked up.

Jerry

[hrh]

Best if you check the SCR anode to cathode with a megger (insulation tester) set at 500V.
Also reverse the + and - leads of the megger to reverse the polarity when testing each SCR.

Check if the fuses blow for M03 or M04 direction. This may clarify which set of SCR is faulty or which part of the circuit is malfunctioning.

Also try to disconnect the 200V ac from the drive which supply the cooling fan on the motor.
You possibly need a technical person who knows the drive and can check the firing and current signals with an oscilloscope. (Recommended, these drives can be tricky)

[Jerry Shorter]

Hrh, Thanks for the jinput. It occured to me to try checking the SCR's with a megger but I didn't know if it would work or not. So I will try that.

Jerry

[jdeere4250]

how is the accl/deccl is it rough, to aggressive?
does it run smooth at commanded speed ?
possibly it either needs Hybrid chip on the pcb replaced or the dither adjusted.
What is the part num of Drive unit?

[Jerry Shorter]

Originally Posted by jdeere4250 how is the accl/deccl is it rough, to aggressive? does it run smooth at commanded speed ? possibly it either needs Hybrid chip on the pcb replaced or the dither adjusted. What is the part num of Drive unit?

When running the accl/deccl is smooth also it runs very smooth at speed.
Drive = A06B-6041-H106
Top board = A20B-0008-037/02 060

It has been running a couple of days now with no problem.

Thanks for the reply.
Jerry

[Zoner]

Odd that it's working again after blowing fuses almost immediately...

I don't know if this is irrelevant...

If the original fuses were slow-blow and were replaced with ordinary (or worse - quick-blow) fuses then this might have been the cause?

The slow-blow fuse just rides out the initial current surge when the motor starts.

This caused me a headache a long time ago (I replaced the original fuse with all we had in stock with the same amps rating). It kept blowing within a couple of seconds of the motor starting, until I decided to read the small print on the fuse! Heh.

[Jerry Shorter]

Originally Posted by Zoner Odd that it's working again after blowing fuses almost immediately... I don't know if this is irrelevant... If the original fuses were slow-blow and were replaced with ordinary (or worse - quick-blow) fuses then this might have been the cause? The slow-blow fuse just rides out the initial current surge when the motor starts. This caused me a headache a long time ago (I replaced the original fuse with all we had in stock with the same amps rating). It kept blowing within a couple of seconds of the motor starting, until I decided to read the small print on the fuse! Heh.

Hi Zoner: The original and what the book calls for are "quick action semi-conductor fuses" What I have ended up doing is to install another fuse block with type T fuses which are fast actiing fuses but half the price and a lot easier to get. although they are 70 amp not 75. Seems to be working.

thanks for the reply, Jerry

[cnc-it]

This problem sounds to me like you are maybe getting dampness in the spindle drive. This can cause arcing when the drive powers up and it will blow those fast acting fuses.

Baisically when the air is warm and dry - no fuses blow, if you get a cold damp day the fuses will blow but the arcing will take away any moisture. So when you put new fuses in again it works fine!

The moisture can actually cuse srews on the chassis to rust and cause permanent arcing problems too.

Sounds daft but it's happened to me.

John

[Jerry Shorter]

Thanks for the reply John. Thats is something that I totally didn't think of. I'll check it out.

Jerry