A UHF technique for advanced PD measurements on inverter-fed motors

This paper deals with partial discharge measurements on inverter-fed motors. They are performed by means of a broadband sensor-filter system which allows partial discharge signal to be recorded, damping the noise generated by the commutation interference of electronic power supply. In this way, on-line or off-line measurements can be carried out with the purpose of evaluating the presence of partial discharges in adjustable speed drives, which often constitute the main cause of winding insulation degradation and premature breakdown. An off-line testing technique is also proposed to offer an insight into PD activity and a more precise location of PD sources. These techniques can allow improved quality control and diagnostics on power-electronic controlled motors.