[mrwhittle]

Last week I was doing a chucking job on a mori seiki sl15 with a fanuc 10tf control. Almost through with the job. Put a part in, closed the collet, and pushed the cycle start button....nothing. couldn't get an alarm number on the crt at all. I opened the cabinet and there it was, the dreaded AL-12. I sent the fanuc spindle drive to a repair facility to have it gone over. I got it back on Thursday (quick service) and installed it yesterday. Double & triple checked the wiring to make sure it was correct. I flipped the breakers on the main panel, then flipped the power switch on the end of the machine. The hydraulic pump and cooling fans came on, then I pushed the start buton on the control.....good so far. When I released the e-stop button, the machine shut down and tripped the 50A breakers in the main panel. I pushed the
e-stop, turned the machine off and reset the breakers. When I turned
the main switch back on I get AL-4 (fuse blown).
Any thoughts what might have caused this?

Thanks,
Martin

[Al_The_Man]

Hopfully the repair facility replaced the Firing board as well as the IGBT's :tired:
And did a complete test on it.
The only other issued is if the motor itself has a problem? Hopefully the fuses went before the drive blew again.
I would replace the fuses and disconnect the motor completely from the drive and power up, if the fuse blows or you get an AL-12, it is most likely the drive again.
If they hang in there with no alarm, check the motor.
Al.

[mrwhittle]

Thanks for the quick reply Al The Man!

I'm not sure what all they did, but they said they replaced all the transistor modules.

I don't have a local source for the fuses, if you're talking about the large screw on fuses. I will order those.

Can I tell anything about the motor with an multi-meter? Also is the spindle motor a standard 3 phase motor that could be wired directly to a 240V 3ph breaker to see if it will run that way, or is that a good way to scortch something?

Thanks again,
Martin

[Al_The_Man]

An ordinary meter will not tell you alot, the best way is to borrow/use a megger, this is a high voltage insulation tester that many electricians will have access to. This will detect if there is a ground on any of the motor phases, If it is not a P.M. 3ph motor (which IIRC it is not) . then it is just a vector drive rated motor so should be possible to hook up to the right 3 ph voltage and test it that way with a clamp on ampmeter and test each phase for balance.
Al.

[mrwhittle]

I'll ask my electrician neighbor if he has one or knows where I can get my hands on one. If not, I might have to wire the motor direct and see if any sparks fly. The motor looks like maybe 15 or 20hp, I'll check it. Do you think 30a fuses will start it with no load?

I sure appreciate your help, Al.
Thanks,
Martin

[Al_The_Man]

On 240 if time delay fuse they should hold in ok.
Al.

[NC Cams]

The velocity drive on my Fanu 5T will pop the fuses INSTANTANEOUSLY if the 3 phase is wired out of phase.

Simply switch any 2 wires of the 3 phase input, problem solved.

Dunno if that will work here but stranger things could happen.

[Arrow Control]

On Fanuc AC drives phasing doesn't matter, I've always been leary of line starting FANUC spindle motors - not sure if they are rated for that inrush. If you do try a megger make sure you disconnect the wires from the drive.....

[mrwhittle]

Thanks for the input!

If I can't borrow a megger, would a cheapie like this do the job?

http://www.grainger.com/Grainger/wwg...mId=1613559264

Thanks,
Martin

[Al_The_Man]

Not really, that is just an ordinary VOM, a megger impresses a high voltage across the circuit being measured, and test if a ground exists at high voltage that may not show up with the couple of volts you have on a VOM.
Another simple way is to use a 120vac circuit, make sure the motor has a ground connection on it to system ground.
Using a 100watt lamp holder with one side connected to 120vac (a hot on an outlet) and the other lamp lead touch to one of the phases, if you get a light it show there is a ground on the motor.
The motor should be vector drive rated which is a higher standard than the regular motor so I don't see any harm running it on 3ph as long as the voltage is correct.
Al.

[mrwhittle]

Now you're getting down to my technology level!!

I'll let you know what happens tomorrow.

Thanks again,
Martin

[NC Cams]

And if you do the lamp bulb trick incorrectly, you could electrocute yourself or someone else. The technique Al used should not be tried by just ANYONE!!!

For example, if you inadvertently catch the ground side of the AC line, you'll get a totally different experience/result than if you touch the "hot" side. Some circuits MAY be wired wrong so don't trust the wire color code - my business partner's shop had some real silly, half fast wiring in it.

"Code? I don't have a code, just some hayfeber" pretty much described his building's wiring...

Experience is needed to prevent some real ugly experiences when you try to do psuedo meggar tests.

Contact a local motor shop. Ask to rent or borrow their meggar. Better yet, plan on paying a service call to have their technician do the meggar test. Doesn't take more than half hour to do the test. Besides, if you can't tell the difference between a VOM and a meggar, outside help may be in order.

Whatever the motor shop charges, it WILL be cheaper than a hospital bill. If the motor is fried (shorted arm or field, they might do the test for free if you have them do the motor repair job.

Cost me $175 to have one pole of a field coil redone and re-varnishe along with meggar check of a unobtainable pancake motor on a Excello mill. I R&R'd and reassebled the motor, they did the arm and field coil check/repair.

Replace bearings while I was at it and had motor armature rebalanced for good measure. The thing is now good for another 25 years of service...

[mrwhittle]

What would be the normal output voltage on a megger, and is it AC or DC?

Thanks,
Martin

[Al_The_Man]

AC and they often have 3 output ranges, 250v 500v and 1000v.
Did you do the test of disconnecting the motor and power the drive up without load?
Al.

[mrwhittle]

If it's always AC, then I've just been "had". I called a company about 50 miles away and they had a service tech headed in my direction, so he came here before going to his other call. I asked him what voltage his "megger" put out,
and he said 500VDC.
According to him the motor checks ok.
Is it time for the light bulb yet?

Martin

[Al_The_Man]

Unless the latest type are DC the old handcrank ones I have been used to are/were AC.
And your sure it was a megger he used, I hope he didn't just use a VOM resistance check ?
Before you go any further, I would still try the drive power on first without the motor, if it blows the fuse or you get a AL-12 alarm then you know the drive is still defective.
Al.

[cncdiag]

Why dont you just leave the motor power cables disconnected.
The drive should come up without any alarms.
If you still get an alarm or fuses blow you have a bad drive.

[mrwhittle]

Unfortunately the three main drive fuses blew when I installed the drive and powered it up, and I don't have spares.

I (very carefully) did the light bulb test, checked to ground, good bright light, checked each lead, not even a flicker.

The company that worked on the drive is sending a tech over one day this week, so maybe he can shed some light on it.

Al
This guy today left his meter here and it's an "Electronic Insulation Tester"

NC Cams
I appreciate your concern, but I'm pretty good at following instructions, and I'm very careful with electricity and large dogs that don't bark!!

Martin

[Al_The_Man]

I have been burnt before by replacing the IGBT transistors without changing the firing board, This may have been the case here, but then it would have happened when they tested it?
Al.

[mrwhittle]

When you say "firing board", are you talking about the main board on the back of the drive?

Martin