If you are commissioning a drive, and the motor does not run, or run properly, you must determine if the problem is the drive, the motor, or the wiring. Executing the basic motor drive troubleshooting checks in a methodical order will help rule out what’s good and pinpoint what’s wrong. to help execute those motor drive diagnostic steps. This guide is specifically written to quickly walk you through steps where the display is dead, motor is not running, or motor is running incorrectly.
Test meters have trouble reading VFD output voltage because an AC motor prefers sinusoidal power, but a variable frequency drive’s output voltage is NOT sinusoidal. As shown below, a VFD’s output voltage is a series square pulses which range from wider to thinner to emulate a sinewave. The following image represents typical voltage output from a VFD.