High peak voltage and extremely rapid voltage pulse rise times cause stress on motor windings and insulation. Modern motor manufacturers are aware of the impact that motor drives have on their products and typically supply products that can withstand these stresses.
However applications involving submersible pumps, long motor cables and older motors require verification that the drive will not cause damage to the motor insulation. If the motor manufacturer recommends protection the following options can be used as appropriate.
dU/dt Filters reduce the rate of voltage rise on the motor terminals and protect old or weak motor insulation against breakdown This can also be particularly important for short motor cables.
Sine Filters smooth the output voltage of a motor drive and reduce motor insulation stress. Bearing currents and noise development within the motor are also reduced.
Common Mode Cores, installed around the three motor phases (U, V, W) reduce high-frequency common-mode currents.