Potential of a Two Motor Concept for Electric Vehicles with Respect to Its Interaction with the Air Conditioning Unit

Abstract

A common approach to enhance the overall efficiency of an electric driven vehicle is to use a double motor concept. In the hereby presented research project TIOM (Two in one motor) two different electric motors are used for traction and the compressor of the air conditioning (AC) system. The main research questions in the following paper are first which operation scenario fits best for this system and second if the developed operation strategy leads to higher efficiencies. For this purpose a simulation model of the vehicle including the AC circuit was built in Dymola. The model contains a strategy that can select between ten different operation modes for the two motors based on the efficiencies of the motors, the torque requirements, the rotation speed of the wheel and the rotation speed range of the AC compressor. The chosen operation scenarios are four driving cycles: the New European Driving Cycle (NEDC), the Worldwide harmonized Light vehicles Test Cycle (WLTC) and two real driving cycles, a regional cycle and a motorway cycle. The simulation also distinguishes between operation with activated and deactivated AC circuit. As a result the energy consumption in the different scenarios is evaluated and compared to a vehicle with a conventional motor concept with separated motors for the traction and AC circuit.