Damage and hardware failure analysis of electric scroll compressor due to unqualified insulation and withstand voltage performance

The common main faults of electric vehicle compressors include scroll plate movement faults, motor module faults, and compressor motor control module faults. Now, we discuss one of the common faults of the compressor - the unqualified insulation and withstand voltage performance of the compressor.
There are three possible reasons for the unqualified insulation and withstand voltage performance of the compressor:
Water ingress into the compressor motor control module or screws left inside the motor control module;
The internal circuit board of the compressor motor control module is burnt out;
The paint on the enameled wire inside the stator of the compressor motor is damaged;
When the insulation and withstand voltage performance of the compressor fails, it is necessary to first analyze whether the leakage part of the compressor is in the motor control module or the motor component. After disassembling the compressor motor control module from the motor, use an insulation withstand voltage tester to test both parts. If there is a short circuit between the high and low voltage harness of the motor control module and the cover plate of the motor control module, it indicates that the insulation withstand voltage of the compressor motor control module is abnormal; If there is a short circuit between the three-phase terminal of the motor and the motor casing, it indicates that the paint film of the enameled wire inside the motor stator is damaged. To lock the fault location, perform the following cause analysis:
Water ingress into the compressor motor control module or screws left inside the motor control module
① As shown in Figure 1, the compressor motor control module is directly buckled onto the top of the casing, with a layer of black waterproof sealing gasket padded in the middle. If the fastening screws between the compressor motor control module and the housing are not locked tightly, there is a gap between the sealing gasket and the housing contact surface or the motor control module bonding surface. When the vehicle passes through a place where the water is too deep or falls from above the compressor, water can easily seep into the compressor motor control module from the gap, resulting in the motor control module being burned out. The high-voltage side of the vehicle determines that there is leakage and directly clamps the high-voltage power supply, The VCU system reported a high voltage interlock fault. At this time, use an insulation and voltage withstand tester to test. Due to the internal water not being dry, the compressor may have an unqualified insulation and voltage withstand performance.
② If installation screws are missing from the motor control module during compressor assembly, it can also lead to NG in the compressor insulation and withstand voltage performance test, which is caused by very few human errors.
Figure 1
Internal circuit board of compressor motor control module burned out
The unqualified quality of electronic components or the non-standard design of PCB boards can lead to the burning of circuit boards. Generally, capacitors are burned in circuit boards, and the possible reasons for causing the burning of capacitors in circuit boards are as follows:
① Extremely unstable voltage; ② The temperature is too high; ③ Harmonic current exists; ④ Unreasonable component selection;
As shown in Figure 2, the copper sheet of the circuit board was burned due to a capacitor explosion in the power supply section. As shown in Figure 3, the carbon powder generated by the capacitor explosion may contaminate the circuit board, causing the motor control module to conduct with the casing, thereby failing the compressor insulation withstand voltage test.
The paint film of the enameled wire in the stator of the compressor motor is damaged
If the compressor motor control module is detected to be free of faults, the cause of compressor leakage is a broken paint film on the motor's enameled wire. There are many reasons for the damage of the paint film on the enameled wire, such as the possibility that the enameled wire may be pulled during the winding process of the motor stator; When employees bend the enameled wire during the process of sorting out the three-phase end of the motor, the paint film may also be damaged; The compressor housing is not clean, and impurities can easily scratch the enameled wire during operation, leading to electric leakage, etc.