Theory Of Operation

Electric and hybrid vehicles are unique in that they incorporate electric motors and electronic control systems designed to operate under heavy loads with extremely high current and voltage demands. As a result, they generate excessive heat during operation. The vehicle incorporates a separate thermal management system known as a power electronics cooling loop to prevent overheating of these critical components. Components cooled by the power electronics cooling loop include: eMotor, On-Board Charging Module (OBCM), Power Inverter Module (PIM), and the DC/DC Converter (DC/DC). The cooling loop is activated any time the vehicle is powered up, including key ON, propulsion system off, and high-voltage battery charging operation. A temperature sensor located within the power electronics cooling loop is utilized to monitor the performance of the cooling loop. This information is supplied to the EVCU for thermal strategy operation. The EVCU will control the coolant pump speed based upon the cooling system needs, and operate the front module cooling fan when necessary. The EVCU controls the on/off function of the pump by a control relay that supplies voltage to the pump when activated. The EVCU controls the speed of the pump through a Pulse Width Modulation (PWM) circuit to the pump. The EVCU monitors the pump for proper control and operation.