Thermal Analysis And Cooling Studies Of Power Control Unit In Electric Vehicles

In order to enhance system level of integration and stability in pure electricvehicles(EV), engineers put drive motor controller, car charger, DC/DC (direct currentto direct current), electric air condition and other power electronic conversion circuitstogether in an aluminum box. The box is called EV integrated power control unit (PCU).Then we can design the system circuit structure, the control unit and drive unit in thePCU. Because of the centralized distribution, the heat from the components is very largeand concentrated. The problem of heat distribution in the system is very important andnot be ignored. This dissertation pays more attention on the crucial heat generatingelement and heat dissipation characteristics in the PCU. It also calculates the heat lossvalues and simulates the cooling systems. The specific content and outcomes are listedbelow:Firstly, the dissertation finds the PCU system’s main heat source and analysis itsthermal characteristics. Internal parts encapsulation structure and radiating mechanismis studied to find the path between heat source and heat sink. By the heat sourcecomponent’s working characteristics, the power loss value can be calculated. The valueis a critical reference to study cooling system.Secondly, on the basis of the principles of heat transfer, fluid-solid coupleddifferential equations are established. These equations provide the theoreticalfoundation of the simulation analysis later. Water cooling thermal resistance model isbuilt to offer a comparison with the emulation results. Some module design relatedparameters are confidential information, which the producers don’t want to offer.According to the concept of equivalent thermal resistance, the simplified3-D numericalmodel is built. The simulation result in Fluent is compared with that in thermalresistance model to verify the correctness and the cooling effect.Finally, for the PCU of different heat loss, there are two heat dissipation structures:the S-style structure for the low loss and pin-fins structure for the high loss. The twostructures are simulated and compared with the calculation value or simulation result toverify the correctness. Some parameters of the structures are changed to find the effecton dissipation. In this paper, the heat loss and heat dissipation in the PCU are studied in thetheoretical analysis, resistance method calculation and numerical simulation in Fluent.The thermal resistance model and the3-D numerical model of the equivalent resistanceare put forward. Some different cooling conformations are simulated in Fluent. Thecalculation and simulation method and results have some theoretical value and strongengineering applications and reference value for the thermal aspects of electric vehicles.