Optimal Flux Weakening in Surface PM Machines Using Fractional-Slot Concentrated Windings

Abstract

Abstract-A design approach is presented for achieving optimal flux-weakening operation in surface permanent-magnet (SPM) synchronous machines by properly designing the machine's stator windings using concentrated, fractional-slot stator windings. This technique makes it possible to significantly increase the machine inductance in order to achieve the critical condition for providing wide speed ranges of constant-power operation. The conditions for optimal flux weakening can be achieved while simultaneously delivering sinusoidal line-to-line back-electromotive-force waveforms and low cogging torque. A closed-form analytical model is described that can be used to design SPM machines to achieve optimal flux-weakening conditions. This technique is applied to design a 6-kW SPM machine that achieves constant-power operation over a wide speed range. Performance characteristics of this machine are compared using both closed-form and finite-element analysis.

Power Loss Evaluation of a Surface Mounted Permanent Magnet Synchronous Machine During Two Hybrid Electric Vehicle Driving Cycles

“…To completely cancel the flux, the current is called short-circuit current I sc . This principle has been shown on the Figure 5 [ Soong et al, 2002;Ef-Refaie et al, 2005;Nguyen et al, 2010;Zhu et al, 2006]. According to Figure 4, the torque-speed characteristic of the driving cycle of the vehicle has shown that there are points where the speed is higher than the base speed (1820 rpm).…”

Surface PM Machine Parameter Selection for Wide Field-Weakening Applications

“…A value of 2/5 was selected [1] because it offers a high winding factor for good utilization of the permanent magnets, provides a large leakage reactance to produce good field-weakening characteristics, and results in low cogging torque.…”

“…However recent work on fractional-slot pitch, concentrated winding (FSCW) surface PM machines has shown that these machines have high values of stator leakage inductance which allows them to achieve a wide constant power speed range (CPSR) [1]. This type of machine has potential for demanding traction applications requiring wide CPSR, high power density and high efficiency.…”

Design considerations for dual winding permanent magnet synchronous machines

“…Permanent magnet synchronous machines (PMSM) with concentrated winding topologies have recently become popular due to simpler and more compact structure as well as some operational advantages such as wider flux weakening range and higher torque output [1,2,8]. Furthermore magnetic isolation feature between coils, which naturally comes with concentrated winding topology, presents some opportunities such as better fault tolerance [3,4] and multi tasked operation as required by some accessory drive system applications in HEVs.…”