New energy electric vehicle insulation fault troubleshooting

First, the detection principle

The testing principle of the insulation performance of pure electric vehicles is essentially to judge the excellent performance by detecting the insulation resistance values of the main positive and negative DC buses of the high voltage circuit to the chassis ground. However, the insulation resistance value of the vehicle can not be directly measured by the relevant detection tools, so the insulation resistance value can be detected by establishing the insulation detection circuit, so as to judge the insulation status of the electric vehicle.

Two, insulation testing tools and testing safety precautions

In the testing and maintenance of pure electric vehicles, special insulation testing instruments should be used to test the insulation performance of high-voltage electrical systems to measure whether the insulation resistance of high-voltage cables and high-voltage components to the body is within the prescribed value range. Commonly used test instruments are digital multimeter, insulation resistance meter, digital insulation tester and so on. Insulation tester tests can only be performed on unpowered circuits. Before testing, ensure that the test circuit or electrical equipment is powered off. When conducting insulation testing for pure electric vehicles, the following safety protection work must be done to ensure the safety of testing personnel.

Set up safety isolation device in the operation area, and place operation warning signs, set up insulation mat to enhance the operation safety. (2) During the detection site and operation process, safety technicians shall be arranged to supervise the whole process. (3) Be sure to check whether high pressure protective gloves, goggles and other instruments and meters meet the safety grade requirements. (4) After all preparations are made, turn off the power supply of the vehicle, pull out the car key at the same time, and leave the vehicle key to the operator alone. Then disconnect the negative electrode of the low-voltage battery to cut off the low-voltage line. When high-voltage operation is involved, the maintenance switch should be removed and kept safely. If there is no maintenance switch, the high-voltage line connection point can be disconnected.

Three, insulation fault troubleshooting and processing of pure electric vehicles insulation fault definition

There are many high-voltage components in the vehicle environment of pure electric vehicles. In order to prevent personal safety risks caused by insulation faults, the vehicle is equipped with a monitoring and detection device for the insulation resistance of the high-voltage components of the vehicle. When the insulation resistance is lower than the set threshold, the insulation fault is determined. When the high voltage insulation fault occurs in a pure electric vehicle, the high voltage insulation fault alarm light is always on, and the following faults may lead to battery disconnection and vehicle inability to run:

(1) Insulation failure of motor system; (2) Insulation failure of motor controller; (3) compressor insulation failure; (4) PTC insulation fault; (5) Insulation failure of high voltage distribution box; (6) Insulation failure of the charger; (7) Insulation fault of battery pack; (8) High voltage wire harness insulation. Generally, the troubleshooting and handling methods of insulation faults are as follows :(1) firstly, try to check whether the fault light can be cleared by repeatedly powering on and off the key. If the fault light cannot be cleared, perform the following methods: (2) The maintenance personnel read the fault through the diagnostic instrument and carry out maintenance according to the specific fault by referring to the maintenance manual; (3) Maintenance personnel must do a good job of high pressure safety protection measures; (4) Pay special attention not to touch the high-pressure parts. The high-voltage wiring harness is marked with special color.