Magnetic Circuit With Meandering Double-Multilayer Air Gap Winding and Halbach Array Configuration for Electric Wheel Hub Drives

• Applicant: Dr.-Ing. Norman Borchardt
• Subject Area: Electrical Energy Systems, Power Management, Power Electronics, Electrical Machines and Drives
• Term: from 2016 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 315694745

Today's electric motors are not necessarily optimal suited for mobile systems. Standard direct current machines, synchronous machines and asynchronous machines have slotted stators with massive iron poles and voluminous copper windings. This results in high motor masses and construction volumes. In fact, potential for lightweight constructions is limited. Because of this, there are a lot of research activities on alternative motor designs.In a first invention a magnetic circuit with air gap winding was developed and patented. This design already allows a so far unrivaled power density of 2 kW/kg for wheel hub motors. During this development period many other innovative ideas, which can improve the power density again, emerged. Because of this, a novel magnetic circuit design with meandering double-multilayer air gap winding and Halbach array configuration for wheel hub drives should be develop with the requested grant.Six aims are defined that build on each other methodically. (1) First, a new magnetic circuit with multi-layer air-gap winding is to develop. Therefore, a meandering multi-layer winding will be mounted on a thin back iron. This meandering structure enables a simultaneous utilization of all magnetic poles. To analyze the new conversion behavior, a static and transient 3D model is built in ANSYS/Maxwell. Previously, this novel magnetic circuit design is getting modeled analytically. A torque increase of approximately 50%, with minimal mass increase, is expected. (2) In the second step, a double rotor with double-multilayer air gap winding is to develop. Two separate multi-layer windings can be used for the electromechanical conversion for the first time. Another torque increase of about 90% is expected. (3) Next, a Halbach array is intended. For the first time, this well-known configuration is to design for the novel magnetic circuit layout. The increased magnetic field inside the air gap enables a torque benefit of approximately 10%. The field reduction inside the back iron allows a further reduction of iron mass. (4) In order to analyze the dynamic behavior of the new magnetic circuits, a sensor-controlled commutation (by using two analog Hall switches) and a sensorless commutation (by using the angle-dependent inductance) is to develop by using Matlab/Simulink. (5) In parallel an analytical dimensioning script for all developed magnetic circuits is to develop in the software Maple. The aim is to be able to calculate promptly the novel magnetic circuits energy-optimized, torque-optimized and weight-optimized. (6) Finally, test patterns will be used to validate the innovative magnetic circuits and to verify the developed models.With these novel magnetic circuit designs, extremely high power densities of more than 3 kW/kg can be realized for wheel hub motors. Furthermore, gained results will be patented and published.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professorin Kimberly L. Turner, Ph.D.