VP10-12 Quarter Sub-Harmonic-Based Self-Excited Brushless Wound Rotor Synchronous Machine Topology
Creators: Syed Sabir Hussain Bukhari
and Paavo Rasilo
Publisher: name: IEEE
Year: 2025

In literature, various brushless topologies of wound rotor synchronous machines (WRSMs) have been proposed. These topologies are based on either the third-harmonic field excitation or the sub-harmonic field excitation methods. With the third-harmonic field excitation method, the rotor harmonic winding requires three times the number of poles as the field winding. In contrast, the sub-harmonic-based field excitation method requires half the number of poles as the field winding, reducing the usage of copper and simplifying the rotor structure (as it depends on the number of harmonic winding poles) [1]-[2]. To achieve simplified and self-excited brushless operation of WRSMs, this paper proposes a brushless WRSM based on the quarter sub-harmonic field excitation method. In this topology, a magnetic field at 1/4th of the fundamental frequency is generated in the machine's airgap using a unique armature winding configuration, which combines single and double-layer winding patterns. This arrangement generates both fundamental and quarter sub-harmonic MMF components in the airgap when supplied with current from an inverter and requires 1/4th the harmonic winding poles compared to the rotor field winding to achieve brushless operation. To validate the operation of the proposed topology, finite element analysis (FEA) is performed in JMAG for an 8-pole, 48-slot machine model. The proposed topology, along with the machine model and its winding configuration, are presented in Fig. 1(a)-(c). In the proposed armature winding configuration [shown in Fig. 1(b) and (c)], 6-slots are used for a single-layer winding, and 42-slots are used for a double-layer winding pattern to achieve 8-pole and 2-pole fields in the airgap. The 2-pole quarter sub-harmonic field is used to induce harmonic current in the harmonic winding of the rotor, which is rectified to excite the rotor field winding for brushless operation. The rotor currents and output torque of the machine are presented in Fig. 2(a) and (b). Detailed analysis and optimization of the proposed topology will be presented in the final paper.References: [1] S. S. H. Bukhari, J. Ikram, F. Wang, X. Yu, J. Imtiaz, J. Rodas, and J. -S. Ro, "Novel Self-Excited Brush-less Wound Field Vernier Machine Topology", in IEEE Access, vol. 10, pp. 97868-97878, 2022. [2] S. S. H. Bukhari, J. Yu, M. A. Shah, J. Rodas, M. Bajaj, and J. -S. Ro, “Novel Sub-Harmonic-Based Self-Excited Brushless Wound Rotor Synchronous Machine”, IEEE Canadian Journal of Electrical and Computer Engineering, vol. 45, no. 4, pp. 365-374, Fall 2022.
In literature, various brushless topologies of wound rotor synchronous machines (WRSMs) have been proposed. These topologies are based on either the third-harmonic field excitation or the sub-harmonic field excitation methods. With the third-harmonic field excitation method, the rotor harmonic winding requires three times the number of poles as the field winding. In contrast, the sub-harmonic-based field excitation method requires half the number of poles as the field winding, reducing the usage of copper and simplifying the rotor structure (as it depends on the number of harmonic winding poles) [1]-[2]. To achieve simplified and self-excited brushless operation of WRSMs, this paper proposes a brushless WRSM based on the quarter sub-harmonic field excitation method. In this topology, a magnetic field at 1/4th of the fundamental frequency is generated in the machine's airgap using a unique armature winding configuration, which combines single and double-layer winding patterns. This arrangement generates both fundamental and quarter sub-harmonic MMF components in the airgap when supplied with current from an inverter and requires 1/4th the harmonic winding poles compared to the rotor field winding to achieve brushless operation. To validate the operation of the proposed topology, finite element analysis (FEA) is performed in JMAG for an 8-pole, 48-slot machine model. The proposed topology, along with the machine model and its winding configuration, are presented in Fig. 1(a)-(c). In the proposed armature winding configuration [shown in Fig. 1(b) and (c)], 6-slots are used for a single-layer winding, and 42-slots are used for a double-layer winding pattern to achieve 8-pole and 2-pole fields in the airgap. The 2-pole quarter sub-harmonic field is used to induce harmonic current in the harmonic winding of the rotor, which is rectified to excite the rotor field winding for brushless operation. The rotor currents and output torque of the machine are presented in Fig. 2(a) and (b). Detailed analysis and optimization of the proposed topology will be presented in the final paper.References: [1] S. S. H. Bukhari, J. Ikram, F. Wang, X. Yu, J. Imtiaz, J. Rodas, and J. -S. Ro, "Novel Self-Excited Brush-less Wound Field Vernier Machine Topology", in IEEE Access, vol. 10, pp. 97868-97878, 2022. [2] S. S. H. Bukhari, J. Yu, M. A. Shah, J. Rodas, M. Bajaj, and J. -S. Ro, “Novel Sub-Harmonic-Based Self-Excited Brushless Wound Rotor Synchronous Machine”, IEEE Canadian Journal of Electrical and Computer Engineering, vol. 45, no. 4, pp. 365-374, Fall 2022.