An Online Adaptive Monitoring System for Insulation Resistance of Electric Vehicles

This paper presents a new insulation detection method for electric vehicles. The system mainly consists of sampling circuit, signal transmission and processing parts. Except a high-voltage control MOSFET switch, it needs not special voltage / current sensors. In addition, this paper introduces a digital potentiometer as a reference /bias resistor. According to the estimation values of the isolation resistance, system select different reference/bias resistor to improve the accuracy of test. This paper gives the circuit principle, hardware circuit, software and insulation resistance calculation formula. Test results show that the device can be real-time and accurate detection of a variety of insulation, the error is smaller than traditional method. In accordance with deterioration of the insulation resistance which is detected by this method, system can accurate warns to the driver or cut off the high-voltage power supply.