Abstract
This paper proposes two permanent magnet vernier machines (PMVM) operation modes, for wide-speed and high efficiency operation. In mode-1, the machine operates as a conventional PMVM with a wye connected stator winding mode. In mode-2, the machine stator winding is switched to a wye-delta winding mode. Contrary to the existing dual-inverter PMVM topology with two additional bidirectional thyristor switches, the proposed topology utilizes a single inverter with six additional bidirectional thyristor switches to change mode. A theoretical discussion of the proposed idea is further verified via finite element analysis (FEA) simulations. The basic electromagnetic characteristics, such as the flux linkage, back electromotive force, torque, and phase voltages of the machine are investigated using wye and wye-delta stator winding configurations, and subsequently, compared with the existing topology that used a dual-inverter PMVM. The FEA results show that the proposed PMVM has low over-all losses, consequently resulting in improved efficiency compared to the existing topology. The speed increases by almost 9 times using the proposed single-inverter PMVM. Transient analysis using FEA is also conducted in this paper.
Highlights
Permanent magnet vernier machines (PMVMs) have earned significant research attention due to their special operating principle, referred to as the ‘‘magnetic gearing effect’’ [1]
PMVMs have higher number of rotor pole pairs compared to stator pole pairs and their operating frequencies are higher as compared to the general permanent magnet synchronous machines (PMSMs)
This paper proposes two modes of operation for a PMVM: in mode-1, stator windings are connected in a wye configuration; in mode-2, the stator winding is switched to the wye-delta configuration for improved efficiency and wide-speed range operation
Summary
Permanent magnet vernier machines (PMVMs) have earned significant research attention due to their special operating principle, referred to as the ‘‘magnetic gearing effect’’ [1]. This paper proposes two modes of operation for a PMVM: in mode-1, stator windings are connected in a wye configuration; in mode-2, the stator winding is switched to the wye-delta configuration for improved efficiency and wide-speed range operation. The FEA results of the basic EMF, power, efficiency, and wide-speed range operation are compared with those of the existing dual-inverter PMVM topology. In conventional medium to high-power machines, copper losses are much larger than iron losses; the phase current mainly affects the efficiency of the machine, which in the delta or wye-delta stator winding connection case is low because of the high back EMF. To use the PMVM for wide-speed range operation, the machine was switched from the wye mode to the wye-delta mode, which decreased the back EMF, and decreased the phase voltages of the machine. The FEA results pertaining to the wye and wye-delta modes of the machine were analyzed at a base speed of 300 rpm
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