Why does the measured mains voltage not match the mains voltage readings according to the HMI on ATV61 or ATV71?


26 July 2022

Measured Mains Voltage does not match the Mains Voltage readings of HMI on ATV61/71

Product line:  
Altivar ATV61 and ATV71

All models, all serial numbers

Flat topping or spiking on the input AC waveform. 

The VFD measures the DC bus voltage and calculates the theoretical mains voltage required to produce that voltage.  The HMI's Mains Voltage reading is the calculated value. It is calculated by taking the DC bus value and dividing it by the square root of 2.
A meter measurement reports average RMS voltage.
Irregularities in the voltage waveform generally are not detected by the meter readings.  However, it is the peak voltage that translates to the DC bus and is measured by the VFD.