A: The VFD outputs a Pulse Width Modulation (PWM) waveform, not a utility-frequency sinusoidal wave. It consists of a series of high-frequency voltage pulses (typically in the range of several kHz to tens of kHz), whose fundamental frequency is the motor operating frequency you set (e.g., 50Hz). Ordinary AC clamp meters (especially non-"True 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, and this typically results in significantly lower readings.

You can use the same clamp meter to measure the current on the input side (R/S/T terminals) of the VFD. If the clamp meter reading for the input current is also much lower than the output current displayed by the VFD (for example, only around 7-8A on the input side), this provides strong evidence that your clamp meter is not suitable for measuring the VFD output. Only if the input side current reading is close to the output side displayed value (11.9A) should you suspect an issue with the VFD's internal detection circuit.

For on-site measurement verification, be sure to purchase or borrow a "True RMS" clamp meter