A novel interior permanent synchronous motor for a high end ebike drive chain

This paper presents technical and economical improvements of a newly developed interior permanent magnet synchronous motor (IPMSM) for a high end ebike and compares the improvements with the currently used drive motor. The new external rotor motor was optimized for hilly districts 10-15km/h and flat areas 25-30km/h which represent the main application scope for ebike drivers. Thanks to the varying number of poles and better use of the winding space, the efficiency could be enhanced for all observed operating points for both, motor mode and generator mode. The driver is now able to use the nominal torque of 30Nm for 21min, more than twice as long as with the current motor due to an improved thermal design which uses the bike frame as a huge cooling fin. In addition, not only in motor mode, but also in generator mode, the overall efficiency is higher in all cases than the existing motor. Besides the technical improvements, the visual integration was also improved using a smaller motor with better technical features. Thanks to a partly automated, special test bench, which was developed at the same time, the production of the new machine can be done more rapidly. Thus, the new IPMSM will be mass produced as soon as possible.