A very simple and therefore wide-spread way to control motor speed and torque is to regulate the stator voltage by pulsewidth modulation (PWM). Depending on the modulation type, number of inverter levels, and modulation index of the PWM, various spectral components occur in the supply signal and inject ripple current in the motor phases. This current distortion can cause significant additional losses in the stator and rotor core, permanent magnets, and windings of an electric machine. Therefore, it is important to consider these losses in an early design stage. In this work, an efficient calculation method for harmonics of multilevel PWM signals and generated phase currents with different modulation types is presented. The PWM losses are calculated via 2-D finite element method analyses. The calculation and simulation workflow is realized within the software tool SyMSpace and applied to a three-phase permanent magnetic synchronous machine (PMSM). Loss measurements at different PWM frequencies and load points are conducted on a 3-phase PMSM. Since simulation and measurement results show good accordance, the proposed methods could be validated.

Topology and shape optimization are still rarely applied to problems in electromagnetic design due to the computational complexity and limited commercial tooling, even though components such as electrical motors, magnetic springs or magnetic bearings could benefit from it, either to improve performance (reducing torque ripple and losses through shaping harmonic content in back electromotive force) or reduce the use of rare-earth materials. Magnetic springs are a fatigue free alternative to mechanical springs, where shape optimization can be exploited to a great degree—allowing for advanced non-linear stiffness characteristic shaping. We present the optimization methodology relying on a combination of several approaches for characteristic shaping of magnetic springs through either a modular design approach based on: (i) Fourier order decomposition; (ii) breaking conventional design symmetry; or (iii) free shaping of magnets through deviation from a nominal design using problem formulations such as spline and polynomials for material boundary definitions. Each of the parametrizations is formulated into a multi-objective optimization problem with both performance and material cost, and solved using gradient free optimization techniques (direct search, genetic algorithm). The methodology is employed on several benchmark problems—both academic and application inspired magnetic spring torque characteristic requirements. The resulting designs fit well with the requirements, with a relatively low computational cost. As such, the methodology presented is a promising candidate for other design problems in 2D shape optimization in electrical motor research and development.

A sealless pump, also known as a wet rotor pump or a canned pump, requires a stationary sleeve in the air gap to protect the stator from a medium that flows around the rotor and the pump impeller. Since the sleeve is typically made from a non-magnetic electrically conductive material, the time-varying magnetic flux density in the air gap creates an eddy current loss in the sleeve. Precise assessment of this loss is crucial for the design of the pump. This paper presents a method for calculating the eddy current loss in such sleeves by using only a two-dimensional (2D) finite element method (FEM) solver. The basic idea is to use the similar structure of Ampère’s circuital law and Faraday’s law of induction to solve eddy current problems with a magnetostatic solver. The theoretical background behind the proposed method is explained and applied to the sleeve of a sealless pump. Finally, the results obtained by a 2D FEM approach are verified by three-dimensional FEM transient simulations.