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View Full Version : WHAT HAPPENED? VFD or Motor died?



KiddZimaHater
04-01-2013, 06:52 PM
I was humming along nicely today, and suddenly my lathe stopped FAST! Dead in its tracks.
The VFD went black.
Everything turned off.
I checked the breaker, and it was tripped.
Reset it, turned on the VFD, It came to life, then shut off. Tripped the breaker again.
So I disconnected the 3 wires going to the motor, and turned on the VFD.
Everything looked normal.
Turned it off, Re-connected the 3 motor wires, and now the VFD is giving me a "Ground Fault Alarm".
The motor won't start-up.
All wires are connected correctly, and have been for the past 3 years.
I'm Electrically Ignorant, so what do I do now?
Take the motor in for a checkup?
Did something die?

Tony Ennis
04-01-2013, 07:29 PM
Check your manual to see exactly what that error means. It could be you have a wire loose back in the breaker box.

KiddZimaHater
04-01-2013, 07:46 PM
The Alarm says: Earth Fault. Drive has detected earth (ground) fault in motor or motor cable. Check motor Check motor cable.
Well....
I checked the motor cable, and everything looks fine. Nothing loose. It's been wired for 3 years without any problems.
Did something happen internally in the motor?

John Stevenson
04-01-2013, 08:32 PM
Have you got a spare slave motor you can connect to ?

Failing that three mains light bulbs wired in delta Δ

Mike Nash
04-01-2013, 08:44 PM
Two things you can try pretty easily. Kill the AC power prior to disconnecting or reconnecting any wires. Allow at least 3-4 minutes after the display dies before touching the wires.

1) Disconnect all three motor leads and start the drive. If it still trips the drive is bad.
2) Disconnect 2 of the motor leads and leave just one connected - Tape the disconnected leads separately. Now power up and start the drive. If that's OK, try each of the other motor leads, one at a time only, with the same test. If that faults the drive but test 1 above did not, it may be a motor winding grounded in the motor or even a wire grounded. I would not advise connecting two motor leads with one disconnected.

BTW, unless your light bulbs are 230V, John's suggestion might get exciting. I would suggest a Y connection since you are in the US if you want to use light bulbs and that only if you are wired for a 230V motor.

MaxHeadRoom
04-01-2013, 08:45 PM
Most VFD's detect a ground fault on the load, you could check for a ground on the motor with a VOM, but it may only show with a Megger test unless it is a very low resistance fault.
Max.

KiddZimaHater
04-01-2013, 08:52 PM
Well CRAP!!
I was fiddling with it, and reversed two wires as to reverse the motor, just out of curiosity.
When I turned on the power, the VFD went KA-POW!!!, with a pretty Orange spark.
Oh Hell.
What have I done now?

Toolguy
04-01-2013, 08:58 PM
You have released the fabled "Magic Smoke". Your VFD's soul is now in digital heaven.:(

Mike Nash
04-01-2013, 09:09 PM
Well CRAP!!
I was fiddling with it,
What have I done now?

Well at least you now know the drive is bad. It's a shame you can't say yea or nay about the motor yet.

Go ahead and pull all three motor leads and power it up. If that is OK, start it. Wear safety glasses. If it doesn't fault, count your blessings, but I suspect it's dead now.

J Tiers
04-01-2013, 09:17 PM
Instead of powering it up, may I suggest:

1) Ohmmeter check from wires to case......

2) power up, with case solidly grounded, and a suitable light bulb in series with each motor lead. a 40W is fine.... you can still buy those.

If a wire is grounded to case, the ohmmeter will show it, OR the light bulb will light.

240V is 138V to neutral (ground) so it;'s a little hard on the bulbs..... usually low wattage in the 40W area can take the most.


QUESTION:

What brand/type of VFD?

Most VFDs are protected against shorts and grounded wires, although some are not, being only protected against line-to-line shorts. Most of the ones that weren't ground protected before are changing over to being protected as new models come out.

It sounds like you have one motor lead grounded, and the VFD has only two sensors.... you can do that, the third wire should be mathematically known from the other two. Problem is, in a short to ground, the math isn't any good..... if the un-sensed wire is shorted to ground, the VFD doesn't "know" and does not shut down. Dollars to popped IGBTs that your problem is that.

KiddZimaHater
04-01-2013, 09:37 PM
It's an ABB drive, Model acs150 purchased in 2010.
Why would the motor suddenly have one lead grounded, outta nowhere?
I hope I didn't kill that drive. :(

MetalMunger
04-01-2013, 10:30 PM
It's an ABB drive, Model acs150 purchased in 2010.
Why would the motor suddenly have one lead grounded, outta nowhere?
I hope I didn't kill that drive. :(
Drives and motors are ephemeral!
Take the motor to a a good rewind shop and have it completely tested.
Consider the drive a rental whose time has expired you did not kill it it died of natural causes:eek:

MaxHeadRoom
04-01-2013, 11:21 PM
It's an ABB drive, Model acs150 purchased in 2010.
Why would the motor suddenly have one lead grounded, outta nowhere?
I hope I didn't kill that drive. :(

The ABB are fairly high quality, If it was an older motor, it would not be vector rated, it may have not taken kindly subjected to high frequency switching, I always make a practice of fitting a 3 phase inductor in the motor leads, this makes it easier on both motor and VFD.
Max.

willmac
04-02-2013, 08:13 AM
I have had similar problems which puzzled me for a while. A mill with a 3hp motor which I was driving from a VFD. The motor was probably about 30-40 years old. Occasionally, on heavy cuts the VFD would fault and the motor stop. I just restarted and everything was fine for a while. Then it would fault and the RCD would drop out. At that point I started to become more concerned. The fact that the RCD dropped out gave me a clue that something was probably getting leaky to earth. I checked the motor windings resistance to earth with a multimeter and they looked reasonable, but not as high as I thought they should be, especially on one winding. It is hard to really test a motor with a multimeter and be sure, so I took the motor to a rewinder and got them to check it properly. The outcome was insulation beginning to break down, and the motor was not 'economically repairable'. New motor and all was well. Your VFD sounds like it may have suffered some damage, which is unfortunate, but check the motor before you try a new VFD.

Incidentally, the rewinder felt that a VFD might stress the insulation more than conventional 3 phase. I can see some logic behind this, but cannot say whether this was a contributing factor in the failure of my motor.

J Tiers
04-02-2013, 09:32 AM
Incidentally, the rewinder felt that a VFD might stress the insulation more than conventional 3 phase. I can see some logic behind this, but cannot say whether this was a contributing factor in the failure of my motor.

The VFD DOES put a bit more stress on the first few turns of each coil. Motor companies have studied this and found that it really IS only the first few.

However, there is also significant stress on the between-phase coil-to-coil insulation, which is typically hand-placed spacers of insulating material, and also from the care taken to keep the different coil wires separated during assembly.

The "VFD rated" motors do have different insulation, largely due to more care taken in assembly (the wire coating is not an important issue, and the motor companies admit that, even as they tout it), and they also have improved cooling to allow running at much slower speeds without compromising the cooling too much. However, they are premium-priced, and are NOT representative of the standard motors you will find at Grainger, etc.

While VERY new "normal type" motors may have a slightly better insulation, the volts per turn are still low enough that wire-to-wire insulation (usually some form of "varnish" or other thin polymer coating) is not the biggest problem. UL treats wire insulation as if it were not there, for instance, they count the coating as having NO effect as far as insulation to ground. "Real" insulation is the paper and plastic placed between the coil and the metal core, and between adjacent coils of different phases, which is then typically filled with heat-cured varnish in a vacuum tank after winding is finished.

Older motors, more than 20 or 30 years old, tend to have been assembled with more care to properly place the insulation, and thus may actually have BETTER coil-to-coil, and coil-to-ground insulation than newer ones.

When a motor is assembled, the windings are actually beaten into place with a wooden hammer. If not done carefully, this can obviously do damage.... older motors were "built" by skilled people. Newer motors are made in ways intended to avoid having to use "skilled people", and are typically slammed-together as fast as possible, for the average commercial motor. In china, and other places, the above description may be too kind, the varnish tank may be replaced by a quick dip in varnish, or the varnish (which takes time and cost) may be eliminated, etc.....

So an older, carefully assembled motor may actually be better able to "take" the increased voltage stress from a VFD.

That said, time and heat will break down any organic-based insulation, whic h becomes leaky, and at some point the motor needs to be replaced, VFD or no VFD.

MaxHeadRoom
04-02-2013, 11:16 AM
It's an ABB drive, Model acs150 purchased in 2010.
Why would the motor suddenly have one lead grounded, outta nowhere?
I hope I didn't kill that drive. :(

See P9 on the effect of common mode choke or 3ph inductor on the VFD output.
http://www.ab.com/support/abdrives/documentation/techpapers/InstallationConsiderations01.pdf
Max.

Hopefuldave
04-02-2013, 05:36 PM
The ABB are fairly high quality, If it was an older motor, it would not be vector rated, it may have not taken kindly subjected to high frequency switching, I always make a practice of fitting a 3 phase inductor in the motor leads, this makes it easier on both motor and VFD.

Max.
_
Max, can I pick your brains re the inductor please? I'd like to fit one to preserve my lathe's 60 year old, three speed, irreplaceable motor, was yours bought in or home brewed? If home brewed, what size of core is it built on, etc? I've looked for 'em on line, but they seem very pricey this side of the pond...
Could I get away with three separate inductors, one per phase? Seems to me that it should work, and those I've seen on mfrs' web sites look very much like three inductors sharing a box...

Dave H. (the other one)

MaxHeadRoom
04-02-2013, 05:50 PM
They usually are designed to share the same core.
I have usually purchased them, either from one of the Transformer manufacturers or from the VFD supplier themselves.
Here they average around $100.00 .
I have never lost a motor, so I figure it has been worth it!.
www.pulseelectronics.com/download/3100/g019
Max.

lakeside53
04-02-2013, 07:54 PM
Here's the source I use : http://www.galco.com/shop/RL-MTE-Line-Reactors. You'd typically choose 3% impedance reactor when used for output. Personally.. I rarely bother for 240 volt vfd's.

J Tiers
04-02-2013, 10:02 PM
3 separate will work.

A lossy core is fine, maybe slightly better..... you can, as Forrest has been known to suggest, wind a few turns on a slice of pipe..... it will do a reasonable job, and for sure it won't "ring"..

KiddZimaHater
04-10-2013, 02:06 PM
UPDATE:
The Armature shop called, and said the 3-phase motor checked out just fine... nothing wrong with it.
WHAT-THE-HELL?????
So why did my VFD give me a "Ground Fault" Alarm?, and not spin the motor?
What's going on?
Bad VFD??

JRouche
04-10-2013, 02:23 PM
UPDATE:
The Armature shop called, and said the 3-phase motor checked out just fine...

What's going on?


Bad VFD??

Thats my guess... JR

MaxHeadRoom
04-10-2013, 02:23 PM
Here is one thing to look out for on one particular VFD.


1.10.6 Ground leakage current
The drive is supplied with an internal EMC filter capacitor installed. If the input voltage to
the drive is supplied through an ELCB or RCD, these may trip due to the ground
leakage current. See section 4.3.1 Internal EMC filter on page 16 for further information
and how to disconnect the internal EMC capacitor.

4.3.2 Removing the internal EMC filter
Tab fully inserted: EMC filter fitted
Tab fully extended: EMC filter disconnected

Max.

George Bulliss
04-10-2013, 02:23 PM
Is there a GFI anywhere upstream from the VFD?

KiddZimaHater
04-10-2013, 03:30 PM
No George,
Straight shot from Panel/240 Breaker, then kill switch, then VFD, then motor.
Total run is about 7 feet. 3 feet to VFD, 4 feet to motor, tops.

EVguru
04-10-2013, 03:35 PM
Depending on how the VFD is contructed, there may be insulation pads installed underneath the power semiconductors. I've seen these fail when a spec of swarf gets between the layers. It works it's way through over a number of heat cycles and eventually shorts out.

wierdscience
04-10-2013, 09:56 PM
No George,
Straight shot from Panel/240 Breaker, then kill switch, then VFD, then motor.
Total run is about 7 feet. 3 feet to VFD, 4 feet to motor, tops.

I am assuming you have checked and rechecked the supply voltage and ground as well as the circuit breaker for faults?

J Tiers
04-10-2013, 11:17 PM
Well, you UNHOOKED the motor for testing...... So anything that may have been wrong about the wiring, such as a short to ground via a stray strand of wire, isn't wrong anymore.

At the end of the day, the VFD is dead, and the motor seems to have no problem, so you know what to do. At this point, aside from checking the length of wire carefully for problems, you can replace the VFD and proceed.

macona
04-11-2013, 04:13 AM
I had that old Gorton mill, one day the thing started throwing a GFI fault, I believe this was a mitsubishi VFD. Installed a Square D alitvar in its place and that worked fine, the mitsubishi works fine still on any other motor. Just more leakage current than the mitsu liked.

You might take the motor down and have the insulation checked.

J Tiers
04-11-2013, 09:22 AM
I had that old Gorton mill, one day the thing started throwing a GFI fault, I believe this was a mitsubishi VFD. Installed a Square D alitvar in its place and that worked fine, the mitsubishi works fine still on any other motor. Just more leakage current than the mitsu liked.

You might take the motor down and have the insulation checked.


UPDATE:
The Armature shop called, and said the 3-phase motor checked out just fine... nothing wrong with it.


Seems there is no problem.

lakeside53
04-11-2013, 12:59 PM
Any chance there was condensation on the wires, vfd or in the motor?

legendboy
04-11-2013, 03:40 PM
Depending on how the VFD is contructed, there may be insulation pads installed underneath the power semiconductors. I've seen these fail when a spec of swarf gets between the layers. It works it's way through over a number of heat cycles and eventually shorts out.

I have an AB vfd sitting on my bench that got smoked with a tiny bit of swarf.

MetalMunger
04-11-2013, 05:14 PM
I have an AB vfd sitting on my bench that got smoked with a tiny bit of swarf.

After funeral services for a dead VFD or maybe two life cycle costing may indicate that you made a poor choice in not paying for a NEMA 4 unit up front. You may also view VFD's as an expendable and just go the Huanyang route $182 for a 4HP unit with free shipping on evil bay (hey and only some are DOA :rolleyes:).

KiddZimaHater
04-13-2013, 01:51 PM
WOO HOO!!
My lathe is alive once again!
I got the motor tested, all checked out OK.
So it was a VFD problem.
Well, I bought a new VFD, and checked, double checked, squeezed my cheeks, and hit the 'GO' button.
It's ALIVE!!!
Now, what to do with the fried drive?
Send it in for repairs or inspection?
This was a pricey repair. Why can't I have an inexpensive passion, like quilting or something?

MaxHeadRoom
04-13-2013, 02:28 PM
You can get high end models off ebay much cheaper than the repair is likely to be, strip it for parts, you can make a nice DC supply out of the 3ph rectifier and cap. bank.
Max.

MetalMunger
04-13-2013, 04:16 PM
WOO HOO!!
Now, what to do with the fried drive?


Hey, according to the weather people it's supposed to be 84F in Live Oak a good day for a barbecue and memorial service.:D
You may also celebrate your good fortune in that the motor did not Tango Uniform and take the drive with it.

lakeside53
04-13-2013, 09:50 PM
After funeral services for a dead VFD or maybe two life cycle costing may indicate that you made a poor choice in not paying for a NEMA 4 unit up front. You may also view VFD's as an expendable and just go the Huanyang route $182 for a 4HP unit with free shipping on evil bay (hey and only some are DOA :rolleyes:).

And if you think they are really 4hp in CT mode, I have some oil wells for sale :)

J Tiers
04-13-2013, 09:59 PM
This was a pricey repair. Why can't I have an inexpensive passion, like quilting or something?

Very obviously, you have not priced the sewing machines used for serious quilting....... Many are , I am told, up in the territory of good new machine tools. My mother-in-law and her sister are quilters.

MetalMunger
04-13-2013, 11:09 PM
And if you think they are really 4hp in CT mode, I have some oil wells for sale :)
Please submit a detailed mineral/oil/gas evaluation for said wells by an independent consulting geologist. Any wells located west of the Colville River in the NPR-A that you have active leases on will be given special consideration.

legendboy
04-13-2013, 11:40 PM
After funeral services for a dead VFD or maybe two life cycle costing may indicate that you made a poor choice in not paying for a NEMA 4 unit up front. You may also view VFD's as an expendable and just go the Huanyang route $182 for a 4HP unit with free shipping on evil bay (hey and only some are DOA :rolleyes:).


i actually got that drive for free....didn't really take good care of it
just hooked it up on the wall and sprayed it with chips :cool: