Strength Analysis of Rotor

Rotor design is a complex task which includes input from a series of analyses such as static, dynamics, electromagnetic, thermal analysis.

One important factor that should be mentioned here is the aspect ratio: length to diameter ratio. Low aspect ratio indcates possible issues with critical speeds.

Interconnected parameters are also the following:

  • spin stresses
  • motor torgue
  • rotor dynamic phenomena
  • heat loads


Usually PM motors have a ratio of 1 to 3. Depending on the application the max tangential speed is around 100-250 m/s. During rotational loads stresses are generated on tangential and normal/radial directions.

The tangential speed of rotor is



The radial equilibrium equation




The stress strain vector is: