This paper presents a new concept for brushless excitation of a wound rotor synchronous machine (WRSM) based on the generation and utilization of a subharmonic component of the stator magnetomotive force (MMF). In this method, a dual inverter topology for the stator winding is proposed. The idea is to generate and utilize an additional subharmonic stator MMF component along with the fundamental component. The rotor carries two different windings: 1) excitation winding and 2) field winding. The subharmonic component induces voltage in the excitation winding and feeds the field winding through a rotating rectifier on the rotor. A 2-D finite-element analysis was performed to analyze and verify the proposed brushless WRSM.

This paper introduces a novel topology for generating a spatial third-harmonic current component to excite the rotor field winding of a wound rotor synchronous machine to achieve brushless operation. In this topology, each of the three-phase windings on the stator is connected with a switch in parallel. In particular, two antiparallel thyristors are used to switch during positive and negative half cycles. Two windings are mounted on the rotor of the machine: 1) the harmonic winding and 2) the field winding. Zero-sequence currents are generated, when the switches are closed near zero crossing for a short time interval. Consecutive operation of the switches creates an additional spatial third-harmonic current pulsating in the stator winding. The number of poles of the stator winding and the field winding is the same (four-poles in this case) to intercept the torque generation component of the air-gap flux, whereas, the number of poles of the harmonic windings is adjusted (12-poles in this case) to intercept the harmonic component of the air-gap flux and develop voltage across the harmonic windings. Harmonic voltage is rectified through a rotating rectifier to feed dc current to the field windings. Results verify the proposed topology simulated by a 2-D finite-element method.

This paper proposes a novel brushless synchronous machine topology that utilizes stator sub-harmonic magnetomotive force (MMF) for desirable brushless operation. The sub-harmonic MMF component that is used in this novel topology is one fourth of the fundamental MMF component, whereas, in previous practices, it was half. To achieve the brushless operation, the novel machine uses a unique stator winding configuration of two sets of balanced 3-phase winding wound in 3 layers. For the rotor, additional winding is placed to induce the sub-harmonic component to achieve the brushless excitation. Unlike its predecessors, it utilizes maximum allowable space in the stator to house conductors in all of its slots. To implement the topology, 8-pole, 48-slot sub-harmonic brushless synchronous machine model has been designed. A 2-D finite element analysis (FEA) is used to simulate and validate the performance of the novel machine as a motor. The proposed topology shows better average torque than the existing sub-harmonic wound rotor brushless synchronous machine topologies.

PM Assisted, Brushless Wound Rotor Synchronous Machine brushless excitation;synchronous machine;hybrid excitation;flux weakening; This paper presents a new permanent magnet (PM) assisted topology for a recently introduced brushless wound rotor synchronous machine (BL-WRSM) [1]. The BL-WRSM had a dual-inverter configuration for generating a composite magneto motive force (MMF) with a fundamental component and a subharmonic component. The subharmonic component of the MMF is used for brushless excitation of the rotor. In this paper, additional PMs were introduced on the rotor of the BL-WRSM, making it a hybrid BL-WRSM. We also discussed the flux weakening operation for the hybrid BL-WRSM. The hybrid BL-WRSM offered advantages for starting the machine and provided better performance under full-load conditions. The finite element method (FEM) was used to analyze the performance of the hybrid BL-WRSM, and we compared its performance with BL-WRSM. Finally, prototypes were built with and without the PM-assistance, and experiments were conducted to demonstrate their performance.

Permanent magnet (PM) machines have broad applicability and a rapid output rise due to their good power factor, high efficiency, and power density. However, with the recent high cost, unavailability, and demagnetization issues of PMs, the wound rotor synchronous machine (WRSM) is a better substitute for permanent magnet machines for various applications in terms of price value and controllability. While the WRSM contains issues such as regular maintenance and replacement of brushes and slip rings, this paper introduces a brushless WRSM (BL-WRSM)with concentrated winding having 36 slots and 48 poles, which generates fundamental component and a dominant sub-harmonic component of magneto motive force (MMF). To achieve the brushless operation, the rotor has an additional winding called excitation winding that is connected with the main field winding via a rectifier. This additional winding is used to induce the electromotive force (EMF) by the sub-harmonic MMF component of the stator. The EMF is converted to DC by the rectifier and fed to the main field winding. This BL-WRSM has been developed for dual-speed applications such as washing machines. The machine has been tested for 46 rpm and 1370 rpm. The low-speed mode is for washing and the high-speed mode is for drying clothes. To validate the performance and feasibility, an outer rotor BL-WRSM is designed. The performance was compared with the conventional WRSM (C-WRSM). 2-D finite element analysis (FEA) simulation was conducted using ANSYS Electromagnetic.