Analytical Design of a Hybrid-Excited Wound Field Synchronous Machine for the Improvement of Torque Characteristics

Wenping Chai,Jung-Woo Kwon,Byung-Il Kwon

doi:10.1109/access.2020.2993317

Wenping Chai, Jung-Woo Kwon + Show 1 more

Open Access

https://doi.org/10.1109/access.2020.2993317

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Abstract

This paper proposed a novel hybrid-excited wound field synchronous machine (HE-WFSM) to efficiently use the field torque and reluctance torque. Meanwhile, an analytical method is utilized to achieve the torque-angle consistency principle, which allows the field torque and the reluctance torque to reach their maximum values at the same phase current angle. First, a novel HE-WFSM with two different rotor excitations is proposed. Second, the PMs and the field windings in the rotor are designed by an analytical method based on the magnetic equivalent circuit (MEC) to produce the same magnetic flux in the air gap to obtain the torque-angle consistency. Third, one practical HE-WFSM applied for a small power fan is designed by the analytical method as an example. Finally, all the performances of the proposed HE-WFSM are predicted by the finite element method (FEM), thereby verifying the improved torque characteristics.

Highlights

Wound field synchronous machines (WFSMs) are drawing increasing attention because they are not limited by a magnet and flexible flux regulation in various applications, such as electric vehicles [1], steam turbines [2], and wind turbines [3]
The saliency ratio, which is low in conventional WFSMs, has been improved by using a single air barrier, which contributes to the production of reluctance torque, resulting in high torque density and efficiency [6]
The results show that the average values of the maximum total torque and the utilized reluctance torque in the designed hybrid-excited wound field synchronous machine (HE-WFSM) are greatly increased by 39.4% and 247.9%, respectively, compared with those of the conventional machine

Summary

INTRODUCTION

Wound field synchronous machines (WFSMs) are drawing increasing attention because they are not limited by a magnet and flexible flux regulation in various applications, such as electric vehicles [1], steam turbines [2], and wind turbines [3]. The efficiency and torque/power density of a WFSM is generally lower than that of a permanent magnet synchronous machine (PMSM) because of the copper loss of the rotor winding and the brush system. [14] proposed a HE-WFSM with asymmetrical geometry to displace the reluctance axis by approximately 30 electrical degrees while avoiding a lower generating torque This machine in [14]. When only field winding is active, the direction of the rotor flux linkage phasor is aligned to the rotor pole body, which is defined as dwinding. When field winding and PM are active at the same time, the direction of the total rotor magnetic flux is between the dwinding and dPM , which is defined as df.

TORQUE-ANGLE CONSISTENCY PRINCIPLE

SIMULATION AND EVALUATION

Findings

CONCLUSION