AEGIS® Bearing Protection - Why Shaft Grounding?
Electric Motors Operating on Line Voltage
- Electric induction motors are designed for operation on 3 phase sine wave power - either 50 or 60 Hz.
- The input power is balanced in frequency, phase (120 degree phase shift) and in amplitude.
- Common mode voltage - the sum of the 3 phases always equals zero volts when properly balanced
NOTE: Bearing protection generally not needed except for large frame motors.
Electric Motors Operated by Variable Frequency Drives (VFD)
- When operated by VFD, the power to the motor is a series of positive and negative pulses instead of a smooth sine wave.
- The input voltage is never blanced because the voltage is either 0 volts, positive, or negative with rapid switching between pulses in all three phases.
- The common mode voltage is usually a "square wave" or "6 step" voltage wave form
Bearing protection needed to mitigate electrical discharge machining (EDM) damage in bearings.