A1 Journal article (refereed), original research

Design of a High-Speed Solid-Rotor Induction Machine with an Asymmetric Winding and Suppression of the Current Unbalance by Special Coil Arrangements

Open Access publication

Publication Details
Authors: Di Chong, Petrov Ilya, Pyrhönen Juha
Publisher: Institute of Electrical and Electronics Engineers (IEEE): OAJ / IEEE
Publication year: 2019
Language: English
Volume number: 7
ISSN: 2169-3536
JUFO-Level of this publication: 2
Open Access: Open Access publication


High-speed solid-rotor induction machines (IMs) suffer from higher rotor eddy-current losses ( as a result of the air-gap flux density harmonics) more than any other type of high-speed machines, because of the solid-rotor steel. A double-layer short-pitch asymmetric winding arrangement with prefabricated coils is proposed in this paper to mitigate the solid-rotor losses and enable easier assembly. However, the asymmetric winding also brings some current unbalance because of three-phase asymmetric stator inductances, especially the winding leakage inductances. Current unbalance can cause harmful effects for both the machine and supply, e.g. torque ripples, unbalanced magnetic pulls, and unbalanced thermal loads of the supply network and supply power electronics. Additionally, a three-phase unbalanced current can cause an extra source of electromagnetic emission to the environment, which can be harmful for surrounding electronics and can cause extra eddy-current losses in surrounding solid surfaces (e.g. a metal terminal box). To mitigate the current unbalance, two methods are compared in this paper. The first method is a slight increase of the stator slot height and placing of the coil sides at the top or bottom within the slot height for different phases. The stator slot height is optimized based on the 2-D finite element method (FEM) to achieve the best solution for mitigation of the current unbalance. The other method is based on the results of the first method, the coil side position for a specific phase is further adjusted. Unlike conventional methods of mitigating the current unbalance by power electronics, the proposed method suppresses the current unbalance solely by adjusting the machine design, which avoids extra investments for power electronics devices. In addition, the machine control strategy remains unchanged compared to the traditional one.

Last updated on 2020-20-03 at 10:03