Shaft Grounding – Fulfilling the Promise of Variable Frequency Drives

Overview:

With the rising cost of energy, the use of variable frequency drives (VFDs) is growing at an increasing rate. By optimizing the frequency of a three-phase alternating-current (AC) induction motor’s voltage supply, a VFD controls the motor’s speed and torque while providing energy savings. And, these energy savings can be quite substantial — 20% or more — making VFDs a “green” solution as well as a wise money-saving investment.

However, in order to be truly “green,” a technology must be sustainable as well as energy efficient. Yet the currents induced on motor shafts by VFDs can wreak havoc with motor bearings, dramatically shortening motor life and severely diminishing the reliability of systems. To mitigate these currents and realize the full potential of VFDs, a cost-effective method of shaft grounding is essential.