After nearly 15 years of development, new energy electric vehicles have formed some technical deposits. The selection of pre-charging resistor determines the speed of the vehicle pre-charging time, the size of the space occupied by the pre-charging resistance, the vehicle’s high-voltage electrical safety, reliability and stability.
Pre-charge resistance is in the vehicle high-voltage power on the capacitor at the beginning of the slow charging resistor, if there is no pre-charge resistor, the charging current will be too large to break the capacitor. High-voltage power added directly to the capacitor, equivalent to an instantaneous short-circuit, excessive short-circuit current will damage high-voltage electrical components. Therefore, when designing the circuit, the pre-charging resistance should be taken into account to ensure the safety of the circuit.
There are two places in the high-voltage circuit of the electric vehicle where the pre-charge resistor is used, which are the motor controller pre-charge circuit and the high-voltage accessory pre-charge circuit. The motor controller (inverter circuit) has a large capacitor, which needs to be pre-charged to control the capacitor charging current.
According to the actual design verification found: ceramic resistor is more practical precharge, discharge and other requirements. It has a high specific heat capacity and can absorb high energy during pre-charging in a short period of time.
