Failed VFD capacitors

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Cow

Senior Member
Location
Eastern Oregon
Occupation
Electrician
I just got home from a service call where every single vfd(15-20HP AC Techs), about 8-9 total had smoked in a potato storage. They all had bulging, blown apart capacitors. The customer stated the power went out for about 10 min. and then came back on line but they may have also lost a phase in the process for a short time.

Are the blown capacitors more indicative of a power surge or phase loss? I don't know if I should try and sell them on a surge suppressor or phase fail relay, although I'm sure both would be a good idea. Any recommendations on surge suppressors? This is a 480 wye service.

They have several other potato storages also, this just happened to be the only one running at the time when the power went out.
 

PowerQualityDoctor

Senior Member
Location
Israel
I guess it is surge that happened during the re-closing of the power. This means that the utility had some failure, waited 10 minutes and re-connected the power. If the failure was not cleared, they have huge surge. Even if the failure is cleared, since many loads receive power and startup at the same time, the voltage is unstable.

I would recommend surge protection more than phase drop protection, but even better to delay the reconnection after power failure.
 

charlietuna

Senior Member
Are there power reactors installed prior to the drives, or do the drives have them internal? Original installed drives were hampered with cap failures for the first few years--then manufacturers began recommending reractors be installed on the incoming feed, they even doubled the warentee time period if you installed them! Later they started designing them internally in their units !
 

robbietan

Senior Member
Location
Antipolo City
Are there power reactors installed prior to the drives, or do the drives have them internal? Original installed drives were hampered with cap failures for the first few years--then manufacturers began recommending reractors be installed on the incoming feed, they even doubled the warentee time period if you installed them! Later they started designing them internally in their units !

I go with charlietuna here - line reactors (or isolation transformers) prevents these types of failures
 

kwired

Electron manager
Location
NE Nebraska
May want to find out why POCO had a failure.

Couple years ago here in a small town the POCO had a transmission line (not sure of voltage) fall on a local distribution line 4160 volt. It shut down the entire town and was several hours before it was back on. But after the power was back on I received service calls all over town with things that were damaged by the surge that happened here.
 

charlietuna

Senior Member
If you have line reactors and all this occurred at the same time i would think you had a problem with the utility. I would install a(Certified) data recorder at the service entrance and monitor incoming power for a full month.
 

kwired

Electron manager
Location
NE Nebraska
VFD drive should continue to run during phase failure if lightly loaded if heavy loaded there will not be enough supply to keep up and it should trip. Since your drives are for HVAC they most likely not heavily loaded unless running at or near full speed. Assuming they are for blowers.

I would say you need to look at the surge being the culprit more than the phase loss.
 

Besoeker

Senior Member
Location
UK
I just got home from a service call where every single vfd(15-20HP AC Techs), about 8-9 total had smoked in a potato storage. They all had bulging, blown apart capacitors. The customer stated the power went out for about 10 min. and then came back on line but they may have also lost a phase in the process for a short time.
If it went single phase and the drive didn't detect that it would give the capacitors a hard time.
 

tom baker

First Chief Moderator
Staff member
There are reactors both before/after the drives.

Is there anything I should specifically be looking for when selecting a surge suppressor?

More is better
You get what you pay for

I would look for a unit that costs $300-$400 and put it on the service panel. If there are feeder panels then add one there.

If these are three phase drives than is there a way to inhibit the drive on a phase failure, auto restart when power is back?
 

mxslick

Senior Member
Location
SE Idaho
If it went single phase and the drive didn't detect that it would give the capacitors a hard time.

Sorry but I disagree with that, as it would not impose any more stress voltage-wise than if they had a full three-phase input. If anything the DC bus voltage would drop from the loss of a phase and that would trigger a DC bus low voltage shutdown.

The described failure mode speaks more of a high-voltage surge or sustained overvoltage condition with the incoming AC line.

I have tested a VFD rated for three-phase input only on single phase (with a 1hp motor) and it was hit and miss, sometimes it would run, other times it would shut down with low DC Bus voltage fault. But it did not blow out.
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Single phase versus three phase on the input of the VFD will make no difference as to the voltage stress imposed on the capacitors.

The increase stress on the capacitors comes from the increased ripple current causing increased heating in the capacitors.

-Jon
 
I guess it is surge that happened during the re-closing of the power. This means that the utility had some failure, waited 10 minutes and re-connected the power. If the failure was not cleared, they have huge surge. Even if the failure is cleared, since many loads receive power and startup at the same time, the voltage is unstable.

I would recommend surge protection more than phase drop protection, but even better to delay the reconnection after power failure.


Yep, when you're a hammer everything looks like a nail......
 
I just got home from a service call where every single vfd(15-20HP AC Techs), about 8-9 total had smoked in a potato storage. They all had bulging, blown apart capacitors. The customer stated the power went out for about 10 min. and then came back on line but they may have also lost a phase in the process for a short time.

Are the blown capacitors more indicative of a power surge or phase loss? I don't know if I should try and sell them on a surge suppressor or phase fail relay, although I'm sure both would be a good idea. Any recommendations on surge suppressors? This is a 480 wye service.

They have several other potato storages also, this just happened to be the only one running at the time when the power went out.

Ungrounded power source is a problem for ASD's, you have to make sure that is suitable for such use. In some cases some screws have to be removed to DISCONNECT some filters form the circuits. In some cases it is just not possible.
Capacitors have a limited life, so if these were older drives, the cap's may just have reached their service life of ~10yrs or less.

Potato storage? Sounds like a nasty moist environment, if your drives are in the storage area you're asking for trouble. (Otherwise mentioning the location is irrelevant to the problem.)
 

Cow

Senior Member
Location
Eastern Oregon
Occupation
Electrician
Potato storage? Sounds like a nasty moist environment, if your drives are in the storage area you're asking for trouble. (Otherwise mentioning the location is irrelevant to the problem.)

No, it's in a dry equipment room.

Next time I'll try and keep my initial post more tidy and leave out the meaningless details that bore you.

Gimme a break....:roll:

Thanks to the other responders though, I still haven't been called back to the site but it seems safe to assume it was a surge rather than the phase loss that caused it. I found a surge suppressor blown on another part of the farm as well.
 
No, it's in a dry equipment room.

Next time I'll try and keep my initial post more tidy and leave out the meaningless details that bore you.

Gimme a break....:roll:

Give you a break? It's not the issue of boring detail, it is an issue of including details that could be misleading. Try to put yourself in the readers position who tries to help you then you respond with belittling comment.

NO.

YOU GIMME A BREAK:mad:
 

Cow

Senior Member
Location
Eastern Oregon
Occupation
Electrician
I'm not going to debate this Weressl, this is my last response to you.

I simply stated where the drives were located, I'm not the first OR LAST person to post a question and do this. Since EVERY SINGLE ONE of the other posters were able to somehow look past this VERY MISLEADING DETAIL and look at the actual issue(the power surge), it doesn't really sound like it's a problem.

Thanks.
 

hurk27

Senior Member
I just got home from a service call where every single vfd(15-20HP AC Techs), about 8-9 total had smoked in a potato storage. They all had bulging, blown apart capacitors. The customer stated the power went out for about 10 min. and then came back on line but they may have also lost a phase in the process for a short time.

Are the blown capacitors more indicative of a power surge or phase loss? I don't know if I should try and sell them on a surge suppressor or phase fail relay, although I'm sure both would be a good idea. Any recommendations on surge suppressors? This is a 480 wye service. They have several other potato storages also, this just happened to be the only one running at the time when the power went out.

Ungrounded power source is a problem for ASD's, you have to make sure that is suitable for such use. In some cases some screws have to be removed to DISCONNECT some filters form the circuits. In some cases it is just not possible.
Capacitors have a limited life, so if these were older drives, the cap's may just have reached their service life of ~10yrs or less.

Potato storage? Sounds like a nasty moist environment, if your drives are in the storage area you're asking for trouble. (Otherwise mentioning the location is irrelevant to the problem.)

Must have missed the "480Y" in the OP?:roll:
 
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