# 5hp 480V motor STUMPED



## Sparda (Jan 9, 2012)

Using a SqD E-Flex drive to contrtol a bank of 3-480V 5hp motors for exhaust fans. One of the motors has had to be replaced twice and the other two are only drawing 4.5A @ 60hz they used to draw about 7A. they work perfectly up to about 45hz (app 400V) but that's where they top out. Amp draw on each leg is balanced and the drive seems to be functioning properly. I thought that they may be single phasing but I would expect an increase in current as opposed to a decrease. All suggestions would be appreciated. Have to go about 50ft in the air tomorrow to start troubleshooting.


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## JRaef (Mar 23, 2009)

Sparda said:


> Using a SqD E-Flex drive to contrtol a bank of 3-480V 5hp motors for exhaust fans. One of the motors has had to be replaced twice and the other two are only drawing 4.5A @ 60hz they used to draw about 7A. they work perfectly up to about 45hz (app 400V) but that's where they top out. Amp draw on each leg is balanced and the drive seems to be functioning properly. I thought that they may be single phasing but I would expect an increase in current as opposed to a decrease. All suggestions would be appreciated. Have to go about 50ft in the air tomorrow to start troubleshooting.


If it is stopping at 400V but continuing up to 60Hz, you are going to be saturating those motors. Most likely someone forgot to program the maximum voltage into the drive and left it at the factory default, which is usually 400V for European drives like the Telemecanique (don't fool yourself, it isn't Sq. D any more). But then they did change the maximum frequency to 60Hz instead of 50Hz. That means your V/Hz ratio is going to be all wrong and unnecessarily heating up the motors. If you were drawing 7A on a 5HP motor, that sounds like they are fairly well loaded. Saturating a loaded motor will cause an increase in heat and probably contributed to the ealy demise of your one motor, as well as stressing the others.

So read the manual before you go up in the air, take it with you if you can. Most likely you will have to go through the setup parameters and tell the VFD that you have a 480V system. That's where I would start.


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## Sparda (Jan 9, 2012)

Thank you very much for the help. Clarification: The drive produces an increase in voltage corresponding with an increase in frequency as it should but the motors cease to increase their speed after approximately 45Hz even though they are getting their 480V at 60Hz. The RPMs top out at a speed that is appoximately 1/3 less than when they were initially installed (app 2 months ago) and the amprere draw is balanced on all 3 phases. I have an identical configuration that is working properly.


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## JRaef (Mar 23, 2009)

Sparda said:


> Thank you very much for the help. Clarification: The drive produces an increase in voltage corresponding with an increase in frequency as it should but the motors cease to increase their speed after approximately 45Hz even though they are getting their 480V at 60Hz. The RPMs top out at a speed that is appoximately 1/3 less than when they were initially installed (app 2 months ago) and the amprere draw is balanced on all 3 phases. I have an identical configuration that is working properly.


OK so now you are saying that the drive is stopping at 45Hz? *

If so, there are 3 things that might make that happen:

1) Your drive is programmed for the maximum output frequency to be 45Hz. I know it seems obvious that this would not be the case, but maybe someone did that accidentally. Easy to check.

2) Your SPEED COMMAND SIGNAL is somehow being limited. This could have a number of different causes within itself, so without knowing how you are changing the speed, I can't help you there. But for example if you are using an external potentiometer, you have too much resistance in the pot circuit and it never gets to full voltage on the input. There is also sometimes what's called an "Offset" and "Gain" adjustment for external speed command signals, that may have been accidentally tweaked.

3) Your drive is programmed to automatically lower the commanded frequency when it detects an overload condition. I've just run into that with a Schneider CX drive (brand labeled Hitachi I believe) and this is a function that is NOT defeat-able. So if you have the motor OL protection turned on, it will automatically attempt to keep running by artificially lowering the speed command until the load drops off. Most drives offer this as an option, I just found out that some of these little drives Schneider is selling do it regardless of whether you want it or not. I find that to be an odd feature because it confuses people, but it is what it is with them.

*By the way this doesn't seem to exactly track with your statement about the voltage increasing proportionally. If you have the drive programmed to reach 460V at 60Hz as it should be, 45Hz should mean the output voltage would be 345V, not 400V. 400V should correspond to about 52Hz. So this tells me something is still not right here. If you do not have the motor parameters programmed correctly, this could be the initial cause of your overload.


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## Wireman191 (Aug 28, 2011)

You need line filters and reactors running multiple motors off the same drive.
Correct me if I am wrong, we have always used them because without we would smoke a motor.


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## Sparda (Jan 9, 2012)

The drive does not stop at 45Hz. Sorry for the misunderstanding. It continues on to 60Hz with a corresponding increase in voltage. Line voltage in the plant is about 486V so the ratios of Hz to voltage are pretty consistent across the board. Also, the drive was built specifically for these 3 motors to run in tandem with each other which should eliminate the need for external filters. A new development though: The motor that burned has all the indications of a blowout due to debris contamination in the windings (this is according to an electrician that does the bench testing of motors for us). The contactor associated with this motor smelled as though the coil got hot and two of the overloads show signs of overcurrent (not melted but blued). The other two motors that has an RPM decrease in the air seem to test ok at this point on the bench but their cases have not been opened yet.


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## John Valdes (May 17, 2007)

Wireman191 said:


> You need line filters and reactors running multiple motors off the same drive.
> Correct me if I am wrong, we have always used them because without we would smoke a motor.


Okay. You are wrong. :thumbsup:



Sparda said:


> The drive does not stop at 45Hz. Sorry for the misunderstanding. It continues on to 60Hz with a corresponding increase in voltage. Line voltage in the plant is about 486V so the ratios of Hz to voltage are pretty consistent across the board. Also, the drive was built specifically for these 3 motors to run in tandem with each other which should eliminate the need for external filters. A new development though: The motor that burned has all the indications of a blowout due to debris contamination in the windings (this is according to an electrician that does the bench testing of motors for us). The contactor associated with this motor smelled as though the coil got hot and two of the overloads show signs of overcurrent (not melted but blued). The other two motors that has an RPM decrease in the air seem to test ok at this point on the bench but their cases have not been opened yet.


What contactor? Is it on the load side of the control in front of the motor? This is not a good idea, unless the designer understood what introducing switching on the VFD load side will do? What concerns me most is all the possibilities of bad connections, contacts etc....with the addition of contactors and overloads.
I understand the need for OL protection at each motor. But I do not understand the use of the contactor. That alone is six extra connections.
What are the contactors used for? If they are not critical to the operation, I would eliminate them for the time being and only use the OLR's. I would also check all these load side connections real good. I would make sure the motors are all connected right. If one motor goes, the drive does not know it is just one motor. If one contactor or OLR goes bad or the contacts are suspect the drive does not know. It sees these contactors, OLR's and motor as one motor. Does this make any sense? I hope I am getting my point across.


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## albert (Mar 17, 2011)

Wireman191 said:


> You need line filters and reactors running multiple motors off the same drive.
> Correct me if I am wrong, we have always used them because without we would smoke a motor.


 
I agree that when multiple motors are supplied from a single VFD line reactors are required for each motor. Otherwise the reflecting waves from multiple motors mess up the PTs in the drive.

The other parameter is that the drive should be in volt per hertz mode and not vector mode. 

Regards,

Albert in Oakville


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## Forsythe (Feb 6, 2012)

I would say grab a meter and call them from the drive - 888-778-2733, option 1 then option 4. They can run thru checks and balances to try and identify if the problem is with the drive, or enclosed accessories. Support is available 24/7.


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## John Valdes (May 17, 2007)

albert said:


> I agree that when multiple motors are supplied from a single VFD line reactors are required for each motor. Otherwise the reflecting waves from multiple motors mess up the PTs in the drive.
> 
> The other parameter is that the drive should be in volt per hertz mode and not vector mode.
> 
> ...


You mean load reactors for the output right? I can see where this would be beneficial, but I do not see it as a fix all.
Do you mean a load reactor for each motor or one for all the motors? I am a firm believer in Line Reactors for every single drive unless the drive has one built in. I only recommend load reactors for motors that are great distances form the drive or noise is an issue.
The manufacturer can tell him what they recommend. Most all recommend a line reactor. (supply side). And even sell them at 1/2 price or less in package deals. Motor/Drive combination orders.


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## albert (Mar 17, 2011)

On the load side of the drive there should be overload protection and load reactor for each motor. The drive should not be in vector mode but in volts per hertz.


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## John Valdes (May 17, 2007)

albert said:


> On the load side of the drive there should be overload protection and load reactor for each motor. The drive should not be in vector mode but in volts per hertz.


Who says? I use load reactors, but not for this reason. I did say I can see a benefit for using reactors as anytime you smooth out and clean up a drives output wave it is a good thing.
And I agree regarding the drive settings. Multiple motors should be approached as such. I don't like to make broad statements like that. I would rather say the drive should be programmed for the best possible operation using multiple motors.
Unless you could input multiple feedback device outputs, you could not use the vector setting anyway. The drive in vector mode is looking for one motor with feedback capabilities.
I do get what you are saying. I am just saying the same thing with different reasons.


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## albert (Mar 17, 2011)

Most manufacturers that I use recommend load reactors for dual motor single drive applications.

Reflected waves must be isolated to protect the drive, motors and wirring. The dc pulses created by the drive travel down the motor cables to the motor. The pulses are then reflected back to the drive as reflected waves. The reflection is dependent on the rise time of the drive output voltage, cable characteristics, cable length and motor impedance.

By having two motors,(two different reflected waves) the voltage reflection is combined and peak voltages can be at a destructive level. A single IGBT drive output may have reflected wave transient voltage stresses of up to twice the DC bus voltage between its own output wires.

Regards,

Albert in Oakville

Info from AB.​


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## niteshift (Nov 21, 2007)

Looks like so far I'm the only one with a differant set up. Not my install, I just work here.

Reactors, we have 2. 1 supplies 10 motor/drives, other one supplies 3 motor/drives.The press main brkr is 1600a, fed to the reactors _then_ to the drives switchgear, then to the drives. 13 drives for 13 motors. Motors are 95hp each, 1235hp, combided. 110a each motor, combined total of 1430a. 

My understanding is the reactors condition line + or - a certain %, and supplies a more consistant voltage. Would this be correct in my understanding?
I have pics at home, can post tommorrow if you want.


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## mattsilkwood (Sep 21, 2008)

Has this problem been resolved yet? I'm curious to know what the issue was.


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## niteshift (Nov 21, 2007)

mattsilkwood said:


> Has this problem been resolved yet? I'm curious to know what the issue was.


Just noticed old post. I too would like to know.


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## Forsythe (Feb 6, 2012)

Some things to consider:

Motor lead length - the drive sees the entire lead length to all three motors as one, so add this up and you may need to add some output filters. 

Should have OL protection for each individual motor

What control method is being used? For multi-motor app, this should be VF 2pts. 

What is the switching frequency? For multiple motors, a lower frequency will work better.


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## niteshift (Nov 21, 2007)

*reactors-pics*

reactors at work.









press breaker.1600a









Out of breaker thru wall going to reactors.

Other side of wall.

















Flex to smaller reactor. Larger reactor seen in back.









Larger reactor.









Out of reactors to drives swithgear.









go to next page.


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## niteshift (Nov 21, 2007)

*more reactors*

from reactor more ladder rack, to drives room wall to switch gear for the drives.


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## niteshift (Nov 21, 2007)

*still more reactor pics*

One of the same pics, shows ladder rack out of drives and to each motor, then tried to show whole shot of driveline, didn't capture all of it. 
Comments?


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## swimmer (Mar 19, 2011)

Otherwise the reflecting waves from multiple motors mess up the PTs in the drive.

The other parameter is that the drive should be in volt per hertz mode and not vector mode. 

Regards,

Albert in Oakville[/quote]


Albert, What are PTs? I'm a little new to VFD.


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## JRaef (Mar 23, 2009)

swimmer said:


> Albert, What are PTs? I'm a little new to VFD.


Might be a semantics issue.

PTs for us here in the US means Potential Transformers and there are no PTs in the VFD. But he may have actually meant Power Transistors, in which case he is correct. Reflected waves from multiple motors is a danger to the output transistors in the VFD. As he mentioned later, the transistors themselves will have transient protection but it is expected to be for one motor. With multiple motors you get a chance for the reflected waves to be much higher because they can be additive under the right circumstances. The load reactors become a low pass filter for those transients. So for two motors, one load reactor sized for the VFD output is usually fine, but for 3 or more, it's better to put a separate smaller load reactor sized for each motor circuit. 

Is it absolutely necessary? No, it's just cheap insurance. If you go without, you may get lucky and have the VFD survive for years without trouble. But again that would be luck, and luck is not a good engineering strategy.


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## swimmer (Mar 19, 2011)

JRaef said:


> Might be a semantics issue.
> 
> PTs for us here in the US means Potential Transformers and there are no PTs in the VFD. But he may have actually meant Power Transistors, in which case he is correct. Reflected waves from multiple motors is a danger to the output transistors in the VFD. As he mentioned later, the transistors themselves will have transient protection but it is expected to be for one motor. With multiple motors you get a chance for the reflected waves to be much higher because they can be additive under the right circumstances. The load reactors become a low pass filter for those transients. So for two motors, one load reactor sized for the VFD output is usually fine, but for 3 or more, it's better to put a separate smaller load reactor sized for each motor circuit.
> 
> Is it absolutely necessary? No, it's just cheap insurance. If you go without, you may get lucky and have the VFD survive for years without trouble. But again that would be luck, and luck is not a good engineering strategy.



Thanks JRaef


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