# High amperage on VFD



## jablonski (May 29, 2010)

Ok so I've got a high amperage problem on a motor in a canola processing plant. Here's the info:

Motor: weg brand, 15hp, 14.6A, 600V, 1.25SF, inverter and severe duty, 90' from source, fed with #12 awg.

VFD: allen Bradley power flex 40. 

Ok so we have a line reactor feeding the VFD, load reactor, then the motor 90 feet away. The issue is that at 45hz, we're getting 460V and 14A. At 60hz we're getting 600V but 22.5 amps. That amperage remains for 2 min, then trips out on o/l. Those are readings at the VFD, both on screen and metered. The only difference is I'm seeing 480v @ 45hz and 700v @ 60 hz when metered at the motor. The parameters are set in the VFD and they should be fine. I'm fairly new to the industrial world so any help would be great. Also, all this equipment is new. Thanks,

Jason


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## Wireman191 (Aug 28, 2011)

Motor wired right? All the connections tight? Ive had issues some what like this because of a loose connection. The OL would trip after a short time. The high current draw because of the single phasing.


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## jablonski (May 29, 2010)

The motor is connected in delta. 1-6, 2-4, 3-5, and everything is tight.


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## ilikepez (Mar 24, 2011)

what meter are you using? does it have a low pass filter and are you using that?

edit:

Check this out where it talks about 'Motor Protection' half way through the article:

'Fast changing pulse-width modulation (PWM) voltage pulses in PWM drives can interact with the distributed inductance and capacitance of long motor leads. This, in turn, can result in amplified peak voltages as high as 1,600V at motor terminals. In fact, the longer the cable length, the higher the peak overvoltage at the motor terminals.'

http://ecmweb.com/mag/electric_line_reactors_vfds/

Here is another explanation with a bunch of math:
http://www.yaskawa.com/site/dmdrive.nsf/link2/MNEN-5JFQPL/$file/AR.AFD.05.pdf


Is this what he is seeing guys? That only explain the higher voltage at the end of his leads and not the amperage, which he is reading at the VFD as well as the motor. 

Are you 100% sure you got the settings correct on the VFD?


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## don_resqcapt19 (Jul 18, 2010)

jablonski said:


> The motor is connected in delta. 1-6, 2-4, 3-5, and everything is tight.


If this is a dual voltage motor, the delta connection is for the lower voltage and the wye connection for the higher voltage.


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## oliquir (Jan 13, 2011)

motor is simply overloaded?, how much does it read if you bypass the vfd?


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## jablonski (May 29, 2010)

Thanks so far for all the replies. We used 2 meters, an entry level greenlee clamp and a fluke clamp. Now the nameplate only states "delta" and it only shows the connections that I stated above. Does that mean it's a single voltage motor? I'll check the nameplate tonight, and see if ther are other voltages stamped on it. I'll also go through that article. Thanks.


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## jablonski (May 29, 2010)

I'll also bypass the VFD, to get rid of that possibility.


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## oliquir (Jan 13, 2011)

jablonski said:


> Thanks so far for all the replies. We used 2 meters, an entry level greenlee clamp and a fluke clamp. Now the nameplate only states "delta" and it only shows the connections that I stated above. Does that mean it's a single voltage motor? I'll check the nameplate tonight, and see if ther are other voltages stamped on it. I'll also go through that article. Thanks.


600v motors are often only delta (never seen 300v or 1200v motors!), you can connect it in Y for startup only.


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## John Valdes (May 17, 2007)

jablonski said:


> Ok so I've got a high amperage problem on a motor in a canola processing plant. Here's the info:
> 
> Motor: weg brand, 15hp, 14.6A, 600V, 1.25SF, inverter and severe duty, 90' from source, fed with #12 awg.
> 
> ...


What is the RPM? This is just as important as the other values you mention.
A VFD outputs volts and Hz proportionately. Meaning you should not have 460 volts output at 45 Hz. You are reading the input voltage, not output voltage it seems. You must measure the output voltage and use the keypad screen to see the Hz.
Set the VFD to operate at 30 HZ. You should have 240 volts output. At 15 Hz, you should have 120 volts output. At 60 Hz, you should have 460 volts output.
You have a parameter or multiple parameters set wrong. Have you entered all the motor data into the drive? All of it. Have you verified all the parameters are correct? Have you set maximum allowable output voltage?
Did you follow the quick start guide when you installed the drive and motor? Did you tweek the settings to match the application?
If you answered no to any of these questions, go back and start over again and check all the parameters you set.
If you must, reset the parameters to factory default and start over again. If you do not know how to do this, call AB or the distributor that sold you the motor and drive.

Ps..........You should have a Volts/Hz ratio parameter. How did you set this one?


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## oliquir (Jan 13, 2011)

John Valdes said:


> What is the RPM? This just as important as the other values you mention.
> A VFD outputs volts and Hz proportionately. Meaning you should not have 460 volts output at 45 Hz. You are reading the input voltage, not output voltage it seems. You must measure the output voltage and use the keypad screen to see the Hz.
> Set the VFD to operate at 30 HZ. You should have 240 volts output. At 15 Hz, you should have 120 volts output. At 60 Hz, you should have 460 volts output.


this is a 600v motor not 480v


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## JRaef (Mar 23, 2009)

Eliminate the easy things first. 
1) Is the PF40 rated for 600V? 
2) Did you program it to reach 575V at 60Hz? (most likely the motor is actually rated 575V)
3) Are you sure the motor is sized properly for the load?
4) Did anyone discuss having both a line and load reactor on a PF40 with an AB drives app engineer? They have warnings about that, the voltage drops created by two reactors have to be accounted for in the drive setup, otherwise the drive tries to compensate. 

Don't trust meters on the output of a VFD unless you spent more than 2 weeks pay on them. Most cheap ones, even if they say "true RMS", are incapable of accurately reading the complex waveform coming from a VFD.


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## John Valdes (May 17, 2007)

oliquir said:


> this is a 600v motor not 480v


Sorry I did not read carefully enough. Canada. Looks like the voltage and Hz are proportional. Are you in contact with the vendor?
JRaef asked the questions you should ask yourself.
Is the load reactor right next to the drive?


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## joethemechanic (Sep 21, 2011)

JRaef said:


> Don't trust meters on the output of a VFD unless you spent more than 2 weeks pay on them. Most cheap ones, even if they say "true RMS", are incapable of accurately reading the complex waveform coming from a VFD.



What do you think of analog meters on a vfd output?


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## John Valdes (May 17, 2007)

joethemechanic said:


> What do you think of analog meters on a vfd output?


You are serious right? :blink:


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## oliquir (Jan 13, 2011)

joethemechanic said:


> What do you think of analog meters on a vfd output?


they will work better than a multimeter, they don't care about wave form, but it would look weird to mix old analog meter with vfd :laughing:


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## John Valdes (May 17, 2007)

John Valdes said:


> You are serious right? :blink:





oliquir said:


> they will work better than a multimeter, they don't care about wave form, but it would look weird to mix old analog meter with vfd :laughing:


I assumed an analog meter would not work with a digital signal.


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## jablonski (May 29, 2010)

Wow thanks for all the info guys! I'll work on it on tomorrow's evening shift. I'll double check the parameters, and do some research on line and load reactors. Both of them are on the same wall as the VFD, so only a couple feet apart. Bypassing the VFD is out of question until we are shut down again. 

Learning everyday!


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## John Valdes (May 17, 2007)

joethemechanic said:


> What do you think of analog meters on a vfd output?


We cannot let this question go. "How can an analog meter measure a simulated digital sign wave"? (Thats what a VFD produces). Or any digital output? Is Joe f***ing with us? Or is he nuts?
I say it cannot be done. A digital meter would be required.

One note: Scopes are analog and they are the very best at reading digital and analog signals.


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## ilikepez (Mar 24, 2011)

I believe an analog multimeter rectifies the AC wave then applies a correction factor. As far as I know it doesn't matter that the VFD is producing a stepped AC wave. The analog meter just rectifies it and spits it out.


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## John Valdes (May 17, 2007)

ilikepez said:


> I believe an analog multimeter rectifies the AC wave then applies a correction factor. As far as I know it doesn't matter that the VFD is producing a stepped AC wave. The analog meter just rectifies it and spits it out.


Where the hell is Jraef when you need him. The stepped wave is DC and is digital. It is a simulated sign wave. Not a true AC sign wave.
I wish I had a drive here/present to check. I am certain the analog meter would be of no use on the drive output.
And where is the Mechanic that started this sh**? :laughing:


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## nolabama (Oct 3, 2007)

John Valdes said:


> Where the hell is Jraef when you need him. The stepped wave is DC and is digital. It is a simulated sign wave. Not a true AC sign wave.
> I wish I had a drive here/present to check. I am certain the analog meter would be of no use on the drive output.
> And where is the Mechanic that started this sh**? :laughing:


Are you saying my simpson wont see the voltage coming out of my powerflexes?


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## oliquir (Jan 13, 2011)

analog meter is just a coil which react to intensity of electric signal it doesnt care at all about the form of the wave. if an analog meter doesnt work on the output of vfd then motors would not work also


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## nolabama (Oct 3, 2007)

oliquir said:


> analog meter is just a coil which react to intensity of electric signal it doesnt care at all about the form of the wave. if an analog meter doesnt work on the output of vfd then motors would not work also


I was holding off on asking the how does the motor see it question.


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## jmsmith (Sep 10, 2011)

oliquir said:


> analog meter is just a coil which react to intensity of electric signal it doesnt care at all about the form of the wave. if an analog meter doesnt work on the output of vfd then motors would not work also


Not necessarily true... You might see something on that meter, but chances are it will NOT be the true voltage. Motor doesn't care about clipping, etc. Analog meter does! That is why they only analog equipment I have ever seen used on a drive is a scope... Other than that, DIGITAL equipment is recommended for drive troubleshooting.

Sent from my iPhone using ET Forum


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## JRaef (Mar 23, 2009)

John Valdes said:


> Where the hell is Jraef when you need him. The stepped wave is DC and is digital. It is a simulated sign wave. Not a true AC sign wave.
> I wish I had a drive here/present to check. I am certain the analog meter would be of no use on the drive output.
> And where is the Mechanic that started this sh**? :laughing:


Hey, it's a Holiday! I've been checking in on my iPad but I hate typing on that thing, so I was waiting until I got back to the office.

I keep my old Simpsom 260 for just this exact reason. An iron vane type meter acts as a low pass filter for the DC pulses and actually gives you a fairly accurate reading of RMS voltage. Useless for current though, it has no way to distinguish harmonics from working current, so the readings are virtually meaningless except by comparison (i.e. has the useless value changed recently?). I've got a Fluke 199 Scope Meter for that, but I bought it because I did a lot of VFD troubleshooting and that justified the expense. It's not for everyone, those puppies are not cheap, I think I paid a little over $3K for it. I've compared the voltage readings from both the Fluke and the 260 on the output of a VFD, the 260 is within 2% or so of the Fluke. But on current, +-15-20% different. Like I said, useless.

Also keep in mind that a Simpson 260 is not Cat IV rated, at least mine isn't (it's an oldie). Not really an issue on the load side of a VFD, but not allowed on the line side in most places.


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## jmsmith (Sep 10, 2011)

JRaef said:


> Hey, it's a Holiday! I've been checking in on my iPad but I hate typing on that thing, so I was waiting until I got back to the office.
> 
> I keep my old Simpsom 260 for just this exact reason. An iron vane type meter acts as a low pass filter for the DC pulses and actually gives you a fairly accurate reading of RMS voltage. Useless for current though, it has no way to distinguish harmonics from working current, so the readings are virtually meaningless except by comparison (i.e. has the useless value changed recently?). I've got a Fluke 199 Scope Meter for that, but I bought it because I did a lot of VFD troubleshooting and that justified the expense. It's not for everyone, those puppies are not cheap, I think I paid a little over $3K for it. I've compared the voltage readings from both the Fluke and the 260 on the output of a VFD, the 260 is within 2% or so of the Fluke. But on current, +-15-20% different. Like I said, useless.
> 
> Also keep in mind that a Simpson 260 is not Cat IV rated, at least mine isn't (it's an oldie). Not really an issue on the load side of a VFD, but not allowed on the line side in most places.


Well, at least you're keeping me honest! :lol: I was going by what I was taught about VFDs... I have a Fluke 289 that I use for troubleshooting drives... Never thought about a Simpson, because (as you already stated) it was simply not allowed on the jobsites that I have been on. BTW, mine came from the era when it could be knocked over on its back, and it might have to go to the repair shop! At one time, the movement were real touchy on these!
Have a good day, and thanks for the lesson! :thumbsup:

Sent from my iPhone using ET Forum


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## John Valdes (May 17, 2007)

JRaef said:


> Hey, it's a Holiday! I've been checking in on my iPad but I hate typing on that thing, so I was waiting until I got back to the office.
> 
> I keep my old Simpsom 260 for just this exact reason. An iron vane type meter acts as a low pass filter for the DC pulses and actually gives you a fairly accurate reading of RMS voltage. Useless for current though, it has no way to distinguish harmonics from working current, so the readings are virtually meaningless except by comparison (i.e. has the useless value changed recently?). I've got a Fluke 199 Scope Meter for that, but I bought it because I did a lot of VFD troubleshooting and that justified the expense. It's not for everyone, those puppies are not cheap, I think I paid a little over $3K for it. I've compared the voltage readings from both the Fluke and the 260 on the output of a VFD, the 260 is within 2% or so of the Fluke. But on current, +-15-20% different. Like I said, useless.
> 
> Also keep in mind that a Simpson 260 is not Cat IV rated, at least mine isn't (it's an oldie). Not really an issue on the load side of a VFD, but not allowed on the line side in most places.


Jraef. Thanks for clearing that up. Since I never tried to use an analog meter on the VFD output, It seemed to me that that it would not work. The visual wave on a scope would also mislead to believe it could not measure it. 
Do you have picture of a sign wave vs a simulated VFD sign wave at similar voltage. I think the guys could appreciate the difference between the two.


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## jablonski (May 29, 2010)

Ok I know I'm bringing up an old post of mine, but here's the light at the end of the tunnel. It turns out that the motor is undersized for the application. We had a VFD specialist come down and he said there is nothing wrong with the parameters, setup, etc. We disconnected the load and it all worked fine. Thanks for everyone's input.


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## John Valdes (May 17, 2007)

Thanks for coming back with the final results. I am concerned as to why a VFD specialist was needed to determine the motor and drive were to small? Was this a new application? Who sized it? And how did you manage this long?


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## jablonski (May 29, 2010)

They ran the motor at 50 hertz, and they hit all the moisture numbers they (operators) needed for the canola. Reason for the VFD specialist is that we wanted to make sure we set it up right since this is the first powerflex we've ever used. The company that made the cyclone system were the ones that sized the motor and VFD.


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