A: The VFD outputs a pulse width modulation (PWM) waveform rather than a utility frequency sine wave. It consists of a series of high-frequency voltage pulses (typically ranging from several kHz to tens of kHz), with its fundamental frequency being the motor operating frequency you set (e.g., 50 Hz). Standard AC clamp meters (especially non-RMS types) are designed and calibrated to measure pure 50/60Hz sine waves. They cannot accurately measure the true RMS value of non-sinusoidal waves like PWM (which are rich in harmonics), often resulting in significantly low readings. For field verification measurements, always use an RMS clamp meter.