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Title: Novel stator wound field synchronous machines with permanent magnets on slot openings
Author: Zheng, Mei
ISNI:       0000 0004 7231 0091
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2018
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The hybrid-excited stator slot opening PM machines (HSSPMMs) can be modified from variable flux machines (VFMs) by adding PMs on the stator slot openings. The PMs in HSSPMMs can be utilized to reduce the stator magnetic saturation caused by DC field excitation in VFMs, and hence to enhance the torque density. According to the operation principle, the PM flux of the HSSPMMs is shunted in the stator and can be pushed to the rotor via the air-gap by the flux produced from DC field excitation. Hence, the open-circuit characteristics of the HSSPMMs, such as cogging torque and back-EMF, are negligible. However, the electromagnetic performance can be affected by different DC field excitations. The performance of the HSSPMMs will be increased with the increasing field current but limited when the field current is over-excited due to stator magnetic saturation caused by DC field excitation. In this thesis, novel HSSPMMs are developed by adding PMs in the stator slot openings of the slots for DC windings of DC-excited switched flux machines (SFMs). The PM volume of the novel HSSPMMs is fixed and similar to that of the conventional HSSPMMs for fair comparison. The operation principle and electromagnetic performance of novel HSSPMMs with different rotor poles are investigated. It shows that compared with DC-excited SFMs, the novel HSSPMMs exhibit improved electromagnetic performance and maintain good flux regulation capability. The finite element predicted open-circuit characteristics, e.g. back-EMF and cogging torque, and on-load static torque of the novel HSSPMMs are experimentally validated. Furthermore, based on the conventional HSSPMMs, the HSSPMMs with 'U-shaped' segmental stator can be developed by alternatively removing half of the stator back-irons and PMs. The modular stator HSSPMMs with different rotor pole numbers are optimised and their electromagnetic performance investigated. The modular stator HSSPMMs can also operate as modular stator slot opening PM machines (SSPMMs) without the DC excitation and their corresponding electromagnetic performance is also investigated.
Supervisor: Zhu, Zi-Qiang ; Jewell, Geraint Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available