Effect of Airgap Length on Electromagnetic Performance of Surface Mounted Permanent Magnet Vemier Machine

Abstract

This paper investigates the effect of airgap length on the electromagnetic performance of 3kW surface mounted permanent magnet Vernier (SPM-V) machine. The performance is compared with a conventional surface mounted permanent magnet (SPM) machine with same airgap length using 2D Finite Element Analysis (2D FEA). For each airgap length, the slot/pole number combination for the SPM-V machine is investigated to achieve the optimal performance compared to the conventional SPM machine. The results show that the SPM-V machine can achieve much higher torque capability than the conventional SPM machine at smaller airgap length. However, there is an optimal airgap length beyond which the torque performance of SPM-V machines drops below the conventional SPM counterparts. Moreover, unlike the conventional SPM machines, the power factor of SPM-V machines drops significantly with increase in airgap length.

Effect of Airgap Length on Electromagnetic Performance of Permanent Magnet Vernier Machines With Different Power Ratings

“…3kW, 3MW and 10MW, which has not been reported in the literature. This paper is an extension of the original work presented in [18]. An outer rotor topology, for example, the schematic shown in Fig.…”

Permanent Magnet Vernier Machines for Direct-Drive Offshore Wind Power: Benefits and Challenges

“…The literature review revealed that a vast majority of research works about PM-V machines have been focused on small power ratings in the range of a few kWs. Recently, a few research works investigating the feasibility of PM-V machines for multi-MW direct-drive wind power applications have been published [19]- [24]. This section is dedicated to summarizing the challenges and benefits unfolded in these papers while scaling the PM-V machines from few kWs up to multi-MW power levels.…”

“…The assessment of the torque ripple is very critical for lowspeed high torque direct-drive applications. Similar to low power ratings, the torque ripple of the SPM-V machines was found to be inherently lower than the conventional SPM machines even at multi-MW power levels [20], [24]. The comparison was made without incorporating any torque ripple reduction techniques like PM shaping, skewing, etc.…”

“…The system-level comparisons between the conventional SPM and the SPM-V generators presented in [22] are performed for the same copper loss between these two types of machines. However, to achieve high torque density, the SPM-V machines are generally designed for high τ r ̅ (>2.2) which results in much smaller stator slots than the conventional SPM machines at multi-MW power levels [24]. This in turn makes the copper loss per stator slot surface area much higher than the conventional SPM generators and therefore better cooling technologies might be needed.…”

“…However, most of the research works are largely limited to relatively small scale (up to few kWs) power levels. A few papers have been published in recent years to assess the suitability of Vernier machines for multi-MW power levels [17]- [24]. This paper aims to summarize the work published in these papers providing useful insight into the benefits and challenges of Vernier machines for direct-drive multi-MW offshore wind power applications.…”