The design of automatic test system used for PDIV measurement of inverter-fed motor

In order to study the partial discharge (PD) characteristics and evaluate the insulation conditions of the inverter-fed motor under sinusoidal voltage automatically, a set of automatic test system is designed based on high frequency current transformer (HFCT) detection technologies. In the system six high-voltage relays are connected with three-phase windings and the grounded enclosure of the motor. By controlling the six different high-voltage relays (on or off) through the FPGA and with the help of high speed data processing function of DSP, all the partial discharge inception voltage (PDIV) of the phase-to-phase and phase-to-ground insulations can be measured automatically. To verify the test performance of the system, PDIV of twisted pair with polyimide film was measured firstly, and then the phase-to-phase and phase-to-ground insulations of an inverter-fed motor were tested. The results shows: The PDIV of the twisted pairs is about 1.85 kV. The phase-to-phase PDIV of the tested motor is about 3.25 kV, while the PDIV of each phases to ground is obviously higher, reaching more than 5 kV. Compared with traditional test methods, this system can not only measure the PDIV of insulations in the motor automatically, but also greatly reduce the amount of labor and improve test efficiency and accuracy. Therefore, it is especially suitable for testing and evaluating the insulation conditions of large number of motors so as to prevent premature insulation failures and elongate the durability of the motors.