Variable speed drives are equipped with some degree of protection against ground faults generated on the load (output) side of the drive. This is intended to protect the drive in the event of a fault in the motor leads or the motor itself. Here we examine the causes and effects of these faults on drives, and ways of resolving them.
Variable speed drive (VSD) ground faults are intended to trip the drive before its output power section is damaged. They are typically displayed as “GF” or an analogous code on the drive’s HMI. These faults may also be termed “earth leakage” in some drive manuals. When they occur, they usually indicate problems with the connected cabling or motor, and need to be addressed promptly. Let’s explore some basic causes and corrective measures.
The most common causes of drive ground faults are motor cables shorted to ground, or motor windings shorted to ground. As we have referenced in past articles, the characteristics of the synthesized AC output voltage and current from a pulse width modulated (PWM) variable frequency drive (VFD) can place additional stresses on cables, motor leads and windings. Particularly […]