Defective Drive???

Jraef

Moderator
Staff member
I installed and commissioned so many 503s, in all of the the various iterations (Magnetek, Yaskawa, Saftronics, IDM, Omron, EMS, ElectroMotive, Unico...) its not even funny. It's not an Overload on the motor side, that displays as "OL1", and if it were an overload of the VFD itself, it displays as an "OL2" or "OL3" if it is torque related. If it is over heating because of poor heat sink ventilation, it displays "OH".

99.9999999% of the time when you get a "mysterious" intermittent OC fault, it's because you are experiencing an intermittent ground fault on the output. There is a Residual Ground fault circuit used in the output Hall Effect Transducer system that detects ground current flow up to 50% of the unit current rating and displays as "GF". But if there is an instantaneous increase in current flow to ground at over 50% I[SUB]r[/SUB] or the DC bus current jumps up to over 200% I[SUB]r[/SUB], then the "OC" fault is triggered. I rarely witnessed the DC bus current issue in the wild, but the GF issue was relatively common.

Most likely you are using a 500V megger, am I right? The problem is, the DC pulses coming from a VFD that is getting 493V input are close to 700V, and if you have any standing waves being created by long lead lengths, they could be closer to 2000V. They could easily be punching through insulation in the motor windings or the motor circuit conductors, but not at a level low enough to be seen by the typical 500V megger. Get a 1000V megger and you may see the leakage.

By the way if you ARE using a 1000V megger and still saw nothing anomalous, another possibility is that because it WAS impacted with dust, one (or more) of the Darlington transistors has a cracked case. So under the right circumstances, it's leaking current to the heat sink, i.e. any slight condensation inside of the drive, or it started that way and now there is a carbon trace that makes it increasingly easier to happen each successive time. If that's the case, it's not worth fixing, you will chase the collateral damage into the rabbit hole and spend WAY more than the cost of a new drive.
 

jerjwillelec

Senior Member
Most likely you are using a 500V megger, am I right?
My megger readings came from a FLUKE 1507 at 1000v (See Post #2)

you may see the leakage.
I wish I had more experience with my megger...I don't truly know how to read it other than "pass/fail" :thumbsdown:

By the way if you ARE using a 1000V megger and still saw nothing anomalous, another possibility is that because it WAS impacted with dust, one (or more) of the Darlington transistors has a cracked case. So under the right circumstances, it's leaking current to the heat sink, i.e. any slight condensation inside of the drive, or it started that way and now there is a carbon trace that makes it increasingly easier to happen each successive time. If that's the case, it's not worth fixing, you will chase the collateral damage into the rabbit hole and spend WAY more than the cost of a new drive.
Exactly what I was thinking ;)

Thank you for your input!!
 

mike_kilroy

Senior Member
my experience 2 weeks ago was with customer who used same fluke 1000v megger; it passed each time he tried it: yet ohmmeter showed 27-80k resistance to ground.... traced motor power cable and found it rubbed thru at a pulley it was against.... yet that fluke showed it no resistance to ground: again, ohmmeter showed low R. Anyway, per Jraef good notes, it is well worth your time to follow that cable from the drive to the motor looking for an abrasion....

Do you know what a replacement drive will cost? I would sell you a 7.5hp Hitachi Wj200 sensorless vector for $ 800 & free shipping. You need to know all your options....
 

Besoeker

Senior Member
Most likely you are using a 500V megger, am I right? The problem is, the DC pulses coming from a VFD that is getting 493V input are close to 700V, and if you have any standing waves being created by long lead lengths, they could be closer to 2000V. They could easily be punching through insulation in the motor windings or the motor circuit conductors, but not at a level low enough to be seen by the typical 500V megger. Get a 1000V megger and you may see the leakage.
But see post #23.
Given that the problem has surfaced in the past two weeks, might it be reasonable that those points had been successfully addressed initially rather than becoming a problem after 19 years and 50 weeks?
My experience is that V and dv/dt issues make themselves known in weeks rather than decades.

If that's the case, it's not worth fixing, you will chase the collateral damage into the rabbit hole and spend WAY more than the cost of a new drive.
That's where I stand on this.
 

kwired

Electron manager
I think most of us here who have had experience in the drives field are suggesting replacing the unit.
It's a relatively low cost item and, having seen your pics, the accumulation of dust probably hasn't done the original unit a whole lot of good.
Don't faff around - just replace it.
And try to make sure that the new unit is better protected against the ingress of all that karp.
If the motor is getting deteriorated insulation like Jaref suggested then the motor is what is bad. If you replace the drive and motor is still bad and will still trip the new drive .... don't that make you look like you are just throwing parts at it hoping you eventually get the right part replaced?

And as far as protecting from ingress of dust - you may not be too familiar with grain elevators and other grain handling operations. Yes it is required to design to keep dust out as that dust is a source for hazardous location requirements in the first place. You will not keep all the dust out of everything unless you want to fill enclosures with epoxy or something like that.

Just park your truck with windows closed near a grain unloading site all day where they are actively unloading grain and you will probably find some grain dust inside when you leave later in the day.

You can use the best sealed enclosures available and still get a little something inside at times, after 20 years I would not expect it to be same as it was when new. Electrical rooms are usually sealed off and they use NEMA 1 enclosures, dust does still get in there, but not anywhere the extreme as it can be in production areas.
 
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