Cost-Effective Scheme for a Brushless Wound Rotor Synchronous Machine

Abstract

This paper proposes a new scheme for a brushless wound rotor synchronous machine (WRSM) by generating an additional, two-pole component of magneto-motive force (MMF) with a series-connected additional three-phase winding with the armature three-phase winding. Unlike existing brushless excitation schemes, which use the inverter to inject harmonic currents in the stator windings, the proposed scheme uses series-connected additional winding on the stator with the armature winding in a two-pole configuration. Consequently, as the current flows in the armature winding, it creates a fundamental rotating air gap flux to interact with the field flux. At the same time, additional rotating flux is created from the additional three-phase winding, which cannot synchronize with the field winding. This additional flux can cause the induction of a voltage in a winding with exactly the same number of poles. For this purpose, a harmonic winding is installed in the rotor along with the field winding connected through a diode bridge rectifier, in order to feed the direct current (DC) to the field winding for rotor excitation without an input current from the brush-slip-ring assembly. The 2D finite-element analysis (FEA) was performed to validate the brushless operation of the proposed machine system.

A Novel Sub-Harmonic Synchronous Machine Using Three-Layer Winding Topology

“…Therefore, average number of conductors per slot will be, (40 + 20 In [15] ABC and XYZ windings are both 2-layer windings, and they are housed separately in two equally divided slot-spaces in the stator, where winding ABC has double the number of turns than XYZ as shown in Figure 6. For the machine presented in [15], total number of slots for each phase is 16, where 8 slots are used for winding A and 8 are used for winding X, where A winding has 40 conductors per slot and X winding has 20 conductors per slot. Moreover, the number of conductors per slot is 30 when ABC and XYZ windings overlap.…”

“…Furthermore, three advanced brushless field excitation methods were developed in recent times: harmonic, inductive, and capacitive power transfer [9]. Few major research investigations were done to discover the feasibility of higher-order harmonic and sub-harmonic MMF components to provide adequate power to the WFSM field winding [11][12][13][14][15][16][17]. Higher-order harmonics that are generated from the 3-phase stator MMF were used for a brushless set-up encountering additional harmonic losses [11].…”

“…Even though the topology offers some promising enhancements, the machine still lags the performance of a PMSM. Nonetheless, a cost-effective scheme for a BL-WRSM using sub-harmonic excitation has been proposed in [16]. Moreover, another dual inverter 4 pole BL-WRSM machine based on the sub-harmonic excitation method presented in [17].…”

Design and Analysis of Single Inverter-Fed Brushless Wound Rotor Vernier Machine

“…Dual mode operation was created by portioning the field winding into two groups to generate different rotor poles by changing field coils arrangements. In [16] a cost-effective scheme of brushless WRM is proposed by using a single inverter. This scheme uses a single inverter as opposed to a dual-inverter for the brushless operation of the WRM.…”