You can also search for the tech article "The Effects of PWM Voltage Source Inverters on the Mechanical Performance of Rolling Bearings" by Busse, Erdman, Kerkman, Schlegel and Skibinski. I found it to be very interesting.
Regards,
Roy Gariepy
Maintenance and Reliability Dept.
Dorlastan Fibers LLC.
Goose Creek, South Carolina USA