(1) Measure the insulation resistance of the main circuit of the vector inverter. When measuring the insulation resistance of the main circuit, make sure to disconnect the main power supply, disconnect all main circuit terminals, including the input terminals (R, S, T or L1, L2, L3) and output terminals (U, V, W) and short-circuit the external resistance terminals to prevent high voltage from entering the control circuit. Connect a 500V megohmmeter between the common line and the ground (PE terminal). The megohmmeter indicates that the value is greater than 5MΩ, which is normal. The method for measuring the insulation of the motor cable is to unplug the motor cable from the U, V, W terminals of the vector inverter and the motor, and measure the phase-to-phase and phase-to-ground insulation resistance. The insulation resistance should be greater than 5MΩ. The method for power cable insulation detection is to separate the power cable from the R, S, T or L1, L2, L3 terminals of the vector inverter and the power supply, and measure the phase-to-phase and phase-to-ground insulation resistance. The insulation resistance should be greater than 5MΩ. The method for motor insulation detection is to disconnect the motor and the cable and measure the insulation resistance of each winding of the motor between the terminals of the motor terminal box. The measured voltage shall not be greater than 1000V, but shall not be less than the power supply voltage, and the insulation resistance shall be greater than 1MΩ.

(2) Measure the insulation resistance of the control circuit. To prevent high voltage from damaging electronic components, do not use a megohmmeter or other high-voltage instruments for measurement. Instead, use the high resistance of a multimeter to measure the insulation resistance of the control circuit. The measured value is usually greater than 1MΩ.

(3) Measure the insulation resistance of external wiring. To prevent the high voltage of the megohmmeter from being applied to the vector inverter, when measuring the insulation resistance of an external circuit, the external circuit to be measured must be removed from the vector inverter before measurement. Can the high voltage of the Eurometer be applied to the vector inverter through other circuits? If so, all related connections should be removed.

After the above inspection items are completed, the protection circuit operation inspection should be carried out. It is very important that the protection circuit is always in a safe working state. Therefore, the operating reliability of the protection function under a given value must be checked. The protection functions that should usually be checked are as follows.

(1) Detection of overcurrent protection function. Overcurrent protection is a circuit with many fault actions in the vector inverter control system, and it is also an important circuit for protecting the main circuit components. Usually, the action value is adjusted by simulating overload, and the test can reliably operate and cut off the output under the set overcurrent value.

(2) Detect the phase loss and undervoltage protection function of the vector inverter. When the power supply is phase-lost or the voltage drops abnormally, it will cause a phase change failure of the power unit, resulting in an overcurrent fault, etc. The phase loss and undervoltage signals must be detected immediately, and the control signal must be cut off for protection. The vector inverter can be powered by a regulator on the power input terminal of the vector inverter to simulate phase loss, undervoltage and other faults, and observe whether the relevant protection functions of the vector inverter are phase-lost, undervoltage, etc.