VFD motor insulation

[kimseunghee]

The VFD(inverter) normally creates harmonics during operation. Motor manufacturer states that the insulation class of VFD driven motor should be higher than DOL driven motor in order to avoid deteriation of insulation because of harmonics. Is that true ? What is normal standard in aspect of winding of motor .

 

[Skogsgurra]

Yes, it is very much so. This report covers must of the aspects.

http://www.rema.uk.com/pdfs/vsd1.pdf

But, it isn't the harmonics that create the problems. Harmonics are low frequency components - from 100 Hz to 2+ kHz and are a matter between mains and inverter. Not the motor.

What kills motor insulation is the HF contents of the motor voltage and the associated ringing that the PWM voltages create.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[DickDV]

In North America, about the only standard that you can trust is NEMA's MG1 Part 31. If the motor meets this spec, you have a motor that has been specifically designed and tested for operation on PWM inverter power.

Do not trust such statements as "Inverter Duty", "Inverter Rated", or "Inverter Ready". These are marketing terms with no technical specification to back them up.

If you are elsewhere in the world, there may be similar IEC specs around but I do not know what they are.

 

[waross]

Search this site. There have been some previous discussions on this topic.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[kimseunghee]

Thanks for advices. Does that mean motor should be updgraded anyway ?. Is there any possibility of method compensating on inverter side, without upgrading motor insulation ?
If take a soft starter, then is motor insulation higher than as well ?

 

[itsmoked]

Not typically needed for SStarters.

Using a filter between the motor and the VFD can greatly reduce the voltage spikes seen in the motor. But they aren't cheap. Still it may be a solution for you.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com