PWM Drive Related Bearing Failures


Thread Starter

Michael Griffin

There was a discussion a short time back about motor failures due to bearing currents. For anyone who is interested, there is an article on this subject in "IEEE Industry Applications Magazine", July/August 1999 (one year
The article discusses causes, how to recognise bearing current damage, how the damage occurs, and what can be done to prevent it.

Michael Griffin
London, Ont. Canada
[email protected]
In response to this problem and others caused by PWM inverters, insulation breakdown and cable length limitations, we are considering developing motor drives using our existing sine wave resonant inverter design. We believe that the pure sine wave output of our inverter would eliminate these problems. At this time, we are trying to identify suitable applications. Can you tell me which motor applications suffer the most from these problems?

Thank you,

Jim Donley
Marketing Manager
Spellman High Voltage Electronics Corp.
475 Wireless Blvd.
Hauppauge, NY 11788

Sunil Abeyratne


Can you please direct me to any literature on 'Bearing failures caused by Power Electronic Drives'?

Thank you


Faculty of Applied Technology
The Open Polytechnic of New Zealand
00 64 4 5705512

Some preliminary questions:

Bearing failure initiated by stray electrical currents flowing in shaft-bearing-machine path has a unique pattern.

1) Does such a pattern exist?

2) Does failure involve both bearings?

3) Are bearings sleeve-type or roller-type?
4) Is source to PWM controller grounded (earthed) directly ? Or thru a resistor? Or via an inductive impedance?

5) Has a power-factor capacitor-set (or bank) been included in system?
If so, how is it confiigured, wye or delta? If wye is neutral point grounded (earthed)?

6) Is drive controller directly connected to to supply? Or via an isolation transformer?

Phil Corso, PE
(Boca Raton, FL)

Pascal Poirier

Maybe you could have a look on Drives Manufacturers web sites...

1- Bearing Currents in Modern AC Drive Systems (ABB Technical Guide 5) Go to, then choose Products & Services -> Product Guide -> Drives -> Library of documents -> Technical Guides

2- The Effects of PWM Voltage Source Inverters on the Mechanical Performance of Rolling Bearings Mech.pdf
3- System Electrical Parameters and Their Effects on Bearing Currents Elect.pdf

4- Effect of PWM Inverters on AC Motor Bearing Currents and Shaft Voltages bearing.pdf
Hope this helps...