End Effects and Geometric Compensation in Linear Permanent Magnet Synchronous Generators with Different Topologies

Abstract

Electricity production from ocean waves with different solutions is a topic of major research interest. Many of such designs are based on linear generators that inherently introduce end forces. In this paper, detent force using Maxwell Stress Tensor and induced voltage is initially investigated for two different winding patterns for a generator topology with buried magnets in a finite element software. Two ways of overcoming the end forces are further examined: the first method reduces the magnetic flux variations of the translator between stator and air. The second method aims at countering the end forces at both ends for full active stator area. A comparison is then made between buried and surface-mounted topologies for the second end effect compensation method. Both no-load and load conditions are investigated in the comparison. The end effect compensation shows promising results for both topologies. Some clear similarities of the extended stator used to counter the end forces are also apparent, where the stator extensions completely cover the outer poles of both topologies. The results also indicate a longer full active stator area for the buried topology for the same pole-pitch and stroke length, resulting in a higher average voltage for partial stator overlap.

Power flow in the air gap of linear electrical machines by utilization of the Poynting vector: Part 1 ‐ Analytical expressions

“…It is also estimated what the power flow is for a multi-sided linear electrical machine in the radial direction. It is only the flow far away from the ends of the electrical machine which is considered, since the flow lines have very special behavior around the ends and is, therefore, more easily studied by, for example, FEM-simulations than analytically [25][26][27]. The linear electrical machines are assumed to be multi-pole, balanced, have no imperfections, and, for the tubular linear electrical machine, having an outer stator.…”

Power flow in the air gap of linear electrical machines by utilisation of the Poynting vector: Part 2 ‐ simulations

“…The tangential force can also be referred to as the detent force, which is studied in more detail in refs. [11,14].…”

Linear Permanent Magnet Vernier Generators for Wave Energy Applications: Analysis, Challenges, and Opportunities

“…Furthermore, the longitudinal end effect of linear vernier machines is regarded as the other problem which uniquely exists for linear structures compared to rotational ones. Linear machines have two open ends contrary to the rotational structures, leading to the undesirable longitudinal end effect and causing a high force ripple [32].…”