In this paper, a new consequent-pole hybrid excitation brushless wound field synchronous machine (CpHE-BL-WFSM) with fractional-slot concentrated winding is proposed. The proposed machine inherits the features of a brushless excited topology in which a rotor field is excited through an additional sub-harmonic magnetomotive force generated by the stator winding arrangement. In conventional BL-WFSMs, the zero starting torque and relatively low efficiency compared to that of permanent magnet synchronous machines (PMSMs) makes it difficult to replace expensive PMSMs in low- and medium-power applications. The advantages of the proposed machine are improved efficiency, improved starting torque, and high electromagnetic torque as compared to conventional brushless machines. A 2-D finite-element analysis is conducted to compare the proposed machine with the conventional BL-WFSM topologies. The results reveal that the proposed machine topology exhibits greater efficiency, improved starting torque, high average torque, and improved torque density.

In this paper, a new low-cost small-scale three-phase brushless motor topology is proposed. This is a new topology for self-excitation of brushless wound rotor synchronous motor investigated initially for rated speed. For brushless excitation, the stator is designed to contain two windings, namely, three-phase armature winding and exciter winding. The rotor consists of two windings, i.e. harmonic winding and field winding, and a diode rectifier. An inverter feeds three-phase armature winding which is connected in series through an uncontrolled three-phase rectifier to a single exciter winding. When the current is supplied from the inverter, both the armature and exciter windings are energized eventually producing a flux in the air gap. Since the flux produced by the exciter winding is not synchronized with the field winding, it produces a harmonic to be intercepted by the harmonic winding on the rotor. Eventually, the voltage produced in the harmonic winding is used to feed dc current to the field winding for brushless operation. The results obtained by 2-D finite element analysis validate the brushless operation of the motor. The proposed motor is analyzed basically for topology verification with finite element analysis (FEA) results. Since the topology can be verified, further effort can be put to investigate such low-cost topologies for brushless wound rotor synchronous motor. It can be an alternative to a costly permanent magnet synchronous motor for specific applications.

This paper proposes a fault tolerant operation of a wound field synchronous machine (WFSM) under loss of excitation (LOE) fault in the rotor field winding. A two-mode field excitation scheme is presented, where, the rotor of the WFSM was modified, and an additional harmonic winding is introduced with a rotating bridge rectifier. Mode I is the conventional direct dc supply field excitation using slip-rings and brushes, whereas mode II is the brushless field excitation under an LOE fault, resulting in an unregulated field current. During mode II, a special coil switching is performed in the stator. Consequently, the stator winding creates an additional sub-harmonic component of the magneto-motive force (MMF) in the machine air gap along with the fundamental MMF component. The additional sub-harmonic MMF is induced in the rotor harmonic winding. A rotating diode bridge rectifier mounted on the rotor periphery rectifies the harmonic winding ac, and a stable dc was supplied to the rotor field winding. The decoupling between the additional rotor harmonic winding and stator winding is analyzed. 2-D finite-element analysis (FEA) was performed to analyze the proposed idea. The FEA results were validated by experiments based on a 1-kW prototype.