Rotor Balancing, e-Motor

When a rotor has been manufactured and assembled, balancing test can be initiated. Balancing includes static and dynamic balancing.

Balancing is important so various small irregularities can be minimized such as

  • wrong manufacturing tolerances
  • material defects
  • unsymmetrical irregularities
  • improper manufacturing

Rotor unbalance is a significant test that needs to be performed otherwise the machine will experience high vibrations and variable stresses and at the end a breakdown. Rotor balancing is significant for high speed rotors.

The parts of the rotor that are included for the balancing can be e.g. shaft, rotor core, end rings, etc.

Types of unbalances

There are three main types of unbalances

  • static unbalance
  • coupled unbalance
  • dynamic unbalance

Dynamic unbalance is the sum of the static and the coupled and it is one of the main sources of rotor vibration. In extreme situations, dynamic unbalance can cause failure of rotor and bearings.










Depending on whether mass is going to be added or removed there are two types of balancing, positive balancing and negative balancing. An advanced balancing machine can automate the procedure of balancing. It identifies the location of the balancing, the amount of unbalanced mass, usually in polar coordinate system. At the end the rotor has an unbalance which is less than the permissible balancing.


Typical balancing configuration