Extended range electric vehicles and full battery electric vehicles place much steeper technical demands on motors than mild and full hybrids.
That’s the verdict of Pete Savagian, GM Engineering Director of Hybrid and Electric Architecture and Electric Motors, who was speaking at the SAE 2010 Hybrid Vehicle Technologies Symposium.
Mr Savigan presented a study highlighting the different power and thermal demands on electric motors in a demanding drive cycle with a strong focus on highlighting the thermal benefits of bar wound stator technology compared to a conventional wire wound stator. He noted that greater electrification means higher peak torque and power densities and that the levels of power density required by an all electric drive application is “very different” than that of a hybrid application.
During the study, GM took an aggressive drive cycle with hard acceleration to about 20km/h, followed by wide open acceleration to 130km/h, followed by a cruising and slowdown. It found that a mild hybrid motor would have an average power requirement of about 3.4kW compared to a full hybrid motor at 5.2kW. However, extended range vehicles and battery electric vehicles had an average requirement of more than four times that level at 24.9kW.
GM also set up a thermal analysis meant to compare conventional wire wound stators to bar wound stators and found that bar winding lowers winding resistance 30 per cent or more, which lowers overall losses compared to conventional wound stators.
According to a spokesman for GM, the company will manufacture bar wound motors at its plant in Baltimore.
