39 Over Amperage Alarm

Hello,

I have (2) Mazak SQT10MS machines sitting right next to each other.

Yesterday, I think there was a small spike on the power grid as both machines posted a 'high voltage'(can remember exact words) on the NC monitor. I turned
both machines down and back up. We were operating fine.

Machine 2 is has no problems, but Machine 1 started show a '39 over amperage' alarm randomly. It may be any where in a parts cycle, or at start up.

Not, it seems it is a standing problem. Here is what I can do with the machine.

I power the machine up using the main switch. Let it power up for a for a minute and then power up the NC/monitor. Everything comes up fine with no errors or alarms. I then home out the turret and the rear head. No problems.

Now, whether it is in manual mode or automatic mode, the I get the '39 over amperage' alarm when the spindle starts to ask for power. The spindle may start up fine and run for a few minutes and then alarm out. Or, it may alarm out as soon as I hit go. It will even alarm out in manual mode when I have the RPM of the spindle at '0'. Sometimes I can manually run the spindle RPM's up over 2k rpm only to have it alarm out after a few minutes. So, it is a bit random.

When I go to the back of the machine, here is what I see on the drives:
FR-SF Drive = AL 032

FR-SQJ-2-5.5K = Al 56

I am not sure what the other board is to the left with digits? axis? It is flashing F1/56, F4/56, F2/56.

It seems that this is all related probably to the high voltage that damaged or partially damaged a component somewhere in the machine. But, it all seems related.

From my readings, it seems there may be a transistor(s) damaged or blown?

I contacted Mitsubishi and they gave me a DC-CT adjustments procedure (for over current alarms) to perform on the FR-SF (SF-CA card) for this AL 032. I have not done this yet, as to me it seems the problem is outside the drive because it is affecting both drives and the axis.

Any recommendations on things to check or where to look next before I run through this procedure? I just want to be sure I am dialing in on the root cause.

Thanks in advance for your help and suggestions!

Sincerely
Mike K.

Consulting this document on Pg38 :Mitsubishi AC Spindle Drive FREQROL-SF Maintenance Manual - CNC Manual

Al 56 means other axis is in alarm. So the problem is in the FR-SF

The "other board" probably controls the X & Z axis along with the mill spindle.

Bill

Hello Bill,

Thank you for your input. I wanted to post in order to let you know and others that the problem as been resolved. It think. The machine has been running fine this morning so far. It was alarming out '39 over amperage' every time we went to run the spindle.

We ended up using the document "FR-SF Adjust DC-CT.pdf" that was recommended to me by Mitsubishi Support. As stated on this document, I checked ch40 voltage on the FR-SF drive and it was fine. I checked the ch41 voltage and it was at 85mv. I adjusted VR3 as the document states to read +/- 5mv. I re-powered the machine and it has been running fine without any of these alarms so far. I will update if something should change.

Thanks for the help!
Mike

What control is on this machine? The 32 alarm is specific to the spindle drive (32 alarm was showing on the drive) You may have a drive beginning to go bad. Bad capacitors or other components can cause alarms like this.

Purpose:
This adjustment is necessary for the customer when receiving the drive back from repair. It is also
necessary to adjust when encountering problems with high loads, the Spindle bogging down, and
over current alarms during machining.
Tools Needed:
Multimeter
Small straight tip screwdriver
Instructions:
I. Adjust DC-CT ch40
Note: See Figure 1 for pin locations
A. Connect positive lead of meter to CH 40
B. Connect negative lead of meter to CH9(ground)
C. Set multimeter to DC voltage
D. Turn on main breaker to machine
E. Power up NC.
F. Adjust VR2. Reading should be 0V dc +/- 5mv dc.
II. Adjust DC-CT ch 41
A. Connect positive lead of meter to CH41
B. Connect negative lead of meter to CH9(ground)
C. Adjust VR3. Reading should be 0V dc +/- 5mv dc.
D. Cycle power on machine and run spindle
Appendix:
Figure1



p.s check you PLG sensor and PLG amplifier settings, that is the box on the top of Spindle motor, open it and you will see Amplifier. YOu must have right voltages coming out of phases A, B and Z , if you have Z phase. If PLG isnt providing good waveform, FR-SF will be loosing control over AC motor rotor motion and that can manifest itself in all kind of alarms