# Weird drive problem?



## JRaef (Mar 23, 2009)

Your troubleshooting strategy is sound. 

The only thing I can imagine off the top of my head is that something in the circuit of this drive is erroneously altering the speed feedback. In other words the drive is somehow THINKING it is going 58Hz and all is right with the world, but in reality it is only running at 48Hz. The VFD determines the speed of the motor by looking at very small signal disturbances in the current going to the motor. If there is some sort of problem in that circuit, it could be falsely identifying the errors as real.

Did you check with an external tach (or even just comparing it to the others) to see if the motor is really turning at that slower speed or if the motor speed is fine and the drive display is incorrect?


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## Cow (Jan 16, 2008)

JRaef said:


> Did you check with an external tach (or even just comparing it to the others) to see if the motor is really turning at that slower speed or if the motor speed is fine and the drive display is incorrect?


You know, I never did. After I swapped motor leads and determined it followed the drive I never thought to compare fan speeds by eye. I'm not sure if I could notice a 10hz difference or not though...

Thanks for the help!


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## JRaef (Mar 23, 2009)

I've only done a few C-H / Vacon drives (that's who makes that drive) over the years, they have ALL had weird quirks to them. I had one that kept tripping on high DC bus voltage. It told me on the display that the DC bus was 720V, the trip threshold was something like 785, but it kept tripping anyway. Took it out and replaced it with spare drive at the site, no problems. Sent the drive in to C-H for eval, no problems found. Hooked it up at my shop, no problems. Took it back out to the site, trips on High DC bus! Never did figure that one out, I just left the other drive there and the user bought another spare. My theory was that they have poor noise immunity, ie EMI/RFI that leaks into the main board circuit and messes things up. In my shop, no RFI other than this one drive, but in the field, it was in a C-H MCC along with a dozen other drives. It was only this one drive that had an issue though, so it points to something that is inconsistent in the construction.


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## sparkywannabee (Jan 29, 2013)

You can buy these tach's that come with self adhesive reflecting tape, put a little piece on one of the blades and shine your beam on it, same tach will also take a wheel with set screw on the end for contact measurement if you can do it safely. I used to have to program Siemens Simatic drives with a HIM, if you don't save the values to eprom you will lose them at powerdown, did you doublecheck you still had the correct parameters. Just bought a Vacon drive last month, but was a little one, 2 HP, parameters were punched in by hand.


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## Cow (Jan 16, 2008)

As far as I could tell it had the correct parameters even BEFORE I copied parameter sets. I went through the parameters one by one with the good drive beside it. I only copied parameter sets just in case I missed a parameter hiding somewhere in the drive that I didn't see.

I understand what you're saying about the EEPROM though, I've only seen that problem on some decade old AB softstarts I work on. I've never seen a drive lose parameter sets on power down. That would be a new one for me...


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## JRaef (Mar 23, 2009)

Cow said:


> As far as I could tell it had the correct parameters even BEFORE I copied parameter sets. I went through the parameters one by one with the good drive beside it. I only copied parameter sets just in case I missed a parameter hiding somewhere in the drive that I didn't see.
> 
> I understand what you're saying about the EEPROM though, I've only seen that problem on some decade old AB softstarts I work on. I've never seen a drive lose parameter sets on power down. That would be a new one for me...


Regarding the Siemens experience, it isn't that it loses parameters on power down, it's that in the Siemens drive the HIM is not necessary to run the drive. So when you use it to make changes to the program, the HIM first uploads the drive programming to its own internal EEPROM, then you are making changes only to that EEPROM which then temprarily transfers it to the RAM in the drive so that you can test it. When you are done, you have to take the step of STORING the new programming that you did in the HIM to the EEPROM memory that resides inside the drive. If you fail to take that final step, the work you did on the HIM is lost as soon as you disconnect it.

Not all drives work that way. I don't think the Vacon drives will run without the HIM connected, but I can't remember.


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## tfo (Jun 20, 2013)

Only thing i can really think of is that maybe the "speed" parameter is not set high enough and 48Hz is what coincides with the max speed parameter, but i know you said you copied parameters.


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## sparkywannabee (Jan 29, 2013)

Cow said:


> As far as I could tell it had the correct parameters even BEFORE I copied parameter sets. I went through the parameters one by one with the good drive beside it. I only copied parameter sets just in case I missed a parameter hiding somewhere in the drive that I didn't see.
> 
> I understand what you're saying about the EEPROM though, I've only seen that problem on some decade old AB softstarts I work on. I've never seen a drive lose parameter sets on power down. That would be a new one for me...


What JRaef said. I did not clarify, you have to change a parameter from 0 to 1 to write to Eprom in drive, till than it is only in the RAM. This obviously does not apply to your situation. Just trying to help. You'll probably be fine once you install a new drive.


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## Cow (Jan 16, 2008)

I went to the site today to replace the drive and it was running correctly at 58hz when I got there.

I stopped and restarted it and it still ramped to 58 hz just like it was supposed too.

The customer said he had not touched the drive in the couple days since we had looked at it. He decided to leave it running and just keep an eye on it. 

So now he has a spare drive!:thumbup:


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## JRaef (Mar 23, 2009)

Cow said:


> I went to the site today to replace the drive and it was running correctly at 58hz when I got there.
> 
> I stopped and restarted it and it still ramped to 58 hz just like it was supposed too.
> 
> ...


That the Microsoft method of field repair. Turn it off, turn it back on, repeat until the problem goes away.


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## adamc (Sep 27, 2013)

> the Microsoft method of field repair. Turn it off, turn it back on, repeat until the problem goes away.


LOL you forgot " Is it Plugged in ? "

RFI is as likely as anything..

years ago at a water plant the process would get messed up once in a while..

lots of hair pulling, cause found...

the company had just installed a "service" radio base station to talk to the trucks..
antenna wire was snaked thru (cheated) and existing conduit with signal wires


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## JRaef (Mar 23, 2009)

adamc said:


> LOL you forgot " Is it Plugged in ? "
> 
> RFI is as likely as anything..
> 
> ...


Just had one Monday where the user had a temporary mock-up of a control panel in their shop that was duplicating one in the field. But the mock-up version was causing some pressure sensors to go haywire whenever any one of 4 small drives were running. We isolated everything, but the issue persisted. Everything was wired correctly with shielded Belden cable, properly grounded shields, power wiring to and from the VFDs separated, output power wiring from the VFDs was done with shielded VFD cable grounded at both ends, etc. etc. etc. I found the problem by taking one drive off of the panel, extending the wires, and moving it to a nearby workbench (the other drives were powered off for the test). Signal cleaned right up. If I picked up the drive while it was running and walked toward the panel, the signal would start to go squirrelly again. Turned out to be a cheap 24VDC power supply that was feeding control power to the pressure transducers. Even though the wire was shielded, RFI coming out of the VFD case was bleeding into the cheap power supply itself and getting into the 24VDC circuit. Put in a better power supply, took care of it.

This by the way is also a cautionary tale on using the cheapest 24VDC power supply you can find on Automation Destruct or FleaBay, they are NOT all created equal! This one was a Rhino brand, which I think is what AD sells cheap. Had this happen with a Meanwell brand too. 

Side note: Meanwell has got to be one of the funniest brand names out there. "It doesn't work, but they mean well..."


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## adamc (Sep 27, 2013)

> this by the way is also a cautionary tale on using the cheapest 24vdc power supply you can find on automation destruct or fleabay, they are not all created equal! This one was a rhino brand, which i think is what ad sells cheap. Had this happen with a meanwell brand too.


*amen *


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## Jlarson (Jun 28, 2009)

JRaef said:


> This by the way is also a cautionary tale on using the cheapest 24VDC power supply you can find on Automation Destruct or FleaBay, they are NOT all created equal! This one was a Rhino brand, which I think is what AD sells cheap.


Was it one of those little plastic cased ones? Those suck.


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## JRaef (Mar 23, 2009)

Jlarson said:


> Was it one of those little plastic cased ones? Those suck.


Yes, the cheapest of cheap.


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## Jlarson (Jun 28, 2009)

Yeah those things got nothing going on for them. They let the magic smoke out all the time and like you found have nothing in the filtering department.


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## Cow (Jan 16, 2008)

Meant to post an update a long time ago. The drive did end up failing about two weeks after the first service call. On a Saturday.


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## denny3992 (Jul 12, 2010)

We have a bunch of those svx9000 up to 60hp and they seem to be work horses... Ours are in hostile environments and still last.. Easy to swap out also!


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