Due to the continuous improvement of researched and developed technology of plug-in Electric vehicle, it has been favored by more and more consumers in recent years. As a result, the demand for Electric Vehicle Supply Equipment (EVSE) is also rising, and the market share is gradually expanding. The power of Electric vehicles is provided by electric vehicle supply equipment EVSE through the standardized interface, charging current can up to 80A. The charging handle of electric vehicle supply equipment EVSE generally includes a junction connected to the cable assembly and a handle with pins. In order to prevent handle melting, failure of electric vehicle supply equipment EVSE and electric vehicle damage due to high temperature of handle during charging process, it is necessary to use the high temperature resistant NTC thermistor produced by EXSENSE Electronics Technology Co., Ltd. for temperature monitoring and temperature protection to ensure the safety of charging process.
High temperature resistant NTC thermistor is encapsulated as a temperature sensor in the charging handle of the electric vehicle supply equipment EVSE, which is connected to the ground conductor and high conductor wire of the handle, and the handle also includes a return conductor. The thermistor will change its resistance value according to the temperature change of the handle. When the temperature of the charging handle rises to the critical value, the data will be fed back to the processing system, and then the stop command will be issued to end the charging. Specifically, the temperature sensor comprises a pair of series high temperature resistant NTC thermistor and resistance circuit, the first series thermistor and resistance circuit connecting the high voltage conductor to the ground conductor; The second series thermistor and resistance circuit connect the return conductor to the ground conductor. If one of the NTC thermistor detects abnormal temperature, the current will be transferred to the ground conductor, and the ground fault detector in the electric vehicle supply equipment EVSE of the electric vehicle will trip and end the charging of the electric vehicle.
The resistance value of NTC thermistor decreases with the increase of temperature, and increases on the contrary. Taking advantage of this feature, the function of grounding current protection of electric vehicle supply equipment EVSE can interrupt charging according to the set temperature critical point. It can be seen from the following table that the grounding current through NTC thermistor is determined by temperature:
The use of high temperature resistant NTC thermistor for temperature monitoring, without complex circuit design can end the charging operation when the temperature of charging handle is abnormal, saving production costs and reducing the probability of accidents of electric vehicle power supply equipment EVSE.
