Test Meters Have Trouble Reading VFD Output Voltage

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.

VFD output voltage appears as a series of square pulses