Potentiometer causes motor drive erratic behavior, but only when mounted/grounded

[cathead]

It makes me wonder if the controller may be incorporating a SMPS(switch mode power supply)...Looking at the board, I think so.

 

[FliesLikeABrick]

It makes me wonder if the controller may be incorporating a SMPS(switch mode power supply)...Looking at the board, I think so.

Hard to say and I don't have a trained-enough eye to tell. If it was a typical SMPS I would not expect it to have a physical switch for changing the input voltage between 115 and 230v (but it does). Do you bring this up because you're thinking about switching noise from a SMPS?

 

[Jeff.64]

No no no, it's not a ground loop- the drive is not transformer-isolated from the line- the pot may need to be isolated from the chassis
KB drives are the same way
They usually provide a pot with a nylon shaft and insulating plastic washers to accomplish the isolation
The pot probably has some leakage to ground- it shouldn't but it might so with 50 volts on it you can't ground it or let it leak to ground

If the Minarik has full isolation between the high and low power sections then it shouldn't matter but I don't know how they
deal with the isolation scenario exactly

We use a lot of Minarik drives at work with both PM and wound fields. All of the Minarik drives I've installed/replaced came with a a nylon shaft pot.
However, this link seems to show a metal pot shaft.

Minarik Drives

Buy online from Minarik Drives - pot / connector eleven piece kit - 202-0031. See what is included in kit on our website & login to order now

www.minarikdrives.com

The drives we use: https://www.minarikdrives.com/MM23001C
The our new old stock drive have nylon shafts.

See page 16, 38 and 53 in the attached PDF.

Try calling Minarik. I've called them once around 12 or 13 years ago and they were very accommodating.

Hope this helps.

 

[FliesLikeABrick]

We use a lot of Minarik drives at work with both PM and wound fields. All of the Minarik drives I've installed/replaced came with a a nylon shaft pot.
However, this link seems to show a metal pot shaft.

Minarik Drives

Buy online from Minarik Drives - pot / connector eleven piece kit - 202-0031. See what is included in kit on our website & login to order now

www.minarikdrives.com

The drives we use: https://www.minarikdrives.com/MM23001C
The our new old stock drive have nylon shafts.

See page 16, 38 and 53 in the attached PDF.

Try calling Minarik. I've called them once around 12 or 13 years ago and they were very accommodating.

Hope this helps.

Thanks - indeed I don't have the original pot that came with this drive (and did not know that the genuine ones are plastic). I wonder if that could potentially (heh) somehow be involved. But from an electricity point of view I can't wrap my head around how the metal body and input shaft of the pot could be causing such an issue.

The replacement pots I already ordered yesterday are also metal. If those still have the same issue, I will buy a plastic body+shaft one instead.

 

[FliesLikeABrick]

We use a lot of Minarik drives at work with both PM and wound fields. All of the Minarik drives I've installed/replaced came with a a nylon shaft pot.
However, this link seems to show a metal pot shaft.

Minarik Drives

Buy online from Minarik Drives - pot / connector eleven piece kit - 202-0031. See what is included in kit on our website & login to order now

www.minarikdrives.com

The drives we use: https://www.minarikdrives.com/MM23001C
The our new old stock drive have nylon shafts.

See page 16, 38 and 53 in the attached PDF.

Try calling Minarik. I've called them once around 12 or 13 years ago and they were very accommodating.

Hope this helps.

btw do you know if the pots that come with the drives are linear or logarithmic taper? I was wondering this and could not find any documentation one way or the other. From the panel on the bridgeport drive, I think it would ideally be logarithmic but it got me wondering what ships with the Minarik drives

 

[cathead]

Hard to say and I don't have a trained-enough eye to tell. If it was a typical SMPS I would not expect it to have a physical switch for changing the input voltage between 115 and 230v (but it does). Do you bring this up because you're thinking about switching noise from a SMPS?

Pretty much, Yes. I looked on the web but found no circuit diagram for the MM230001C board. Standard
power supplies(transformer+rectifier type) would not act like that.

From previous posts, it looks like an insulated coupler in line with the variometer shaft would
fix it.

If it does have a SMPS, they run at .3 megahertz or so.....

 

[FliesLikeABrick]

We use a lot of Minarik drives at work with both PM and wound fields. All of the Minarik drives I've installed/replaced came with a a nylon shaft pot.
However, this link seems to show a metal pot shaft.

Minarik Drives

Buy online from Minarik Drives - pot / connector eleven piece kit - 202-0031. See what is included in kit on our website & login to order now

www.minarikdrives.com

The drives we use: https://www.minarikdrives.com/MM23001C
The our new old stock drive have nylon shafts.

See page 16, 38 and 53 in the attached PDF.

Try calling Minarik. I've called them once around 12 or 13 years ago and they were very accommodating.

Hope this helps.

It looks like this drive I am using would have been sold with the Minarik 202-0031 potentiometer kit. Based on ebay and google images results, they all have metal bodies and metal shafts. It is interesting that they ship others with plastic, maybe there is a reason for it on the drives you are using but as far as my problem it sounds like a red herring

 

[markba633csi]

To solve the question once and for all you would disconnect the pot and measure the resistance from the three terminals
to the shell or case. It should be very high like several megohms but probably isn't
The nylon shaft is just an additional bonus to protect the operator against shock, a metal shaft pot should work if it has high enough isolation resistance

 

[FliesLikeABrick]

To solve the question once and for all you would disconnect the pot and measure the resistance from the three terminals
to the shell or case. It should be very high like several megohms but probably isn't

I did do that before posting, it was over 20 megaohms. Same with the other identical pot I tried. My only guess is that it is leaking at voltages over what the dmm uses, since the pot inputs are 50vdc off of earth potential and the dmm tests with a fraction of that. I hope to have different pots early this week to test.

 

[markba633csi]

Hmm that is strange- It could be some kind of weird oscillation perhaps
The 50 volts puzzles me since I see there's a small transformer which
should be isolating the front end of the drive including the pot- the mystery deepens
I'd have to see the schematic