Determining the source of noise in a motor is often much more challenging than correcting it. However, a methodical approach to investigating the noise can narrow down the possible causes and therefore make it easier to resolve the noise issue. There is a caveat. If the cause of the noise is due to something in the motor design, that is, a manufacturing defect or anomaly, a solution may not be possible or practical.

An increasing number of manufacturers are using magnetic wedges in their form-wound machines. When a winder fails to replace magnetic wedges in kind, the winding temperature rise can increase by 20°C, and the magnetizing current can increase by 20% or more.

This paper investigates the impact on the motor performance during starting and normal operation by employing magnetic wedges versus non-magnetic wedges and other potential design changes.