Downsizing possibilities of a PM synchronous motor for a hybrid vehicle

In the project “Twin-drive range-extender (DE-REX)”, an innovative serial-parallel hybrid drive concept is being developed for a test bench and a demonstrator prototype vehicle and evaluated. The electric motors for the powertrain DE-REX are 6-pole interior permanent magnet synchronous machines with distributed round wire winding, buried permanent magnets in V-shape in the rotor and a stator water-jacket cooling. Based on the test bench measurement results of the electric motors a thermal reserve of the electric motors was confirmed. Hence, a concept study was conducted on the downsizing of the electric motors. Based on the measurement data and the requirements of the electric motor for the powertrain DE-REX, first a smaller electric machine with round wire winding without any thermal reserve was designed, which has a reduced active volume by 23%. In a second step, the round wire winding was replaced by a hairpin profile wire wave winding, which allowed a reduction of the active motor volume by 32%, compared to the original electric motor