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Eddy current losses in rotor permanent magnets (PM) of synchronous machines with concentrated windings are calculated for sinusoidal stator currents. Three different calculation methods are compared in the FiniteElement environment: 1) analytical post processing of FE magneto-static data with multi-move and eddy currents calculated from vector potential, 2) direct FE magneto-static method, 3) time stepping with a FE program. From thermal measurements performed on existing prototype motors the losses in magnets are compared based on the temperature rises in the magnets at adiabatic heating.Index Terms--Concentrated windings, eddy current losses, finite-element calculations, permanent magnets.

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The thermal calculation of a 500 kW permanent magnet (PM) motor with surface mounted rotor magnets used for gearless traction in railway applications is discussed. The motor features a water jacket cooling. A 3D time-stepping Finite Element Method (FEM) thermal model in ANSYS is used. The model is parameterized for optimization of the motor thermal utilization. Fault situations are also investigated using a transient calculation. Thermal measurements with a 500 kW prototype motor, performed on a test-rig, are in good concordance with the numerical results.

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Fig. 1. SeaGen gearbox tidal power plant in Strangford Lough, Northern Ireland [2] (©Siemens AG, Germany). The turbines are lifted above the sea level for maintenance.Fig. 2. Concept picture for a tidal stream generator placed on the sea bottom [8] (©TU Munich, Germany).Abstract-The design of a direct drive PM synchronous generator for a tidal stream subsea turbine is presented in this paper. The generator design must comply with a set of very narrow restrictions concerning the available volume, the required output, the maximum current of the threephase marine cable and the inverter maximum voltage. For these reasons the obtained design is not able to completely fulfill the requirements, especially for the case of short time overload. The results show however the feasibility of the concept. With a relatively small correction of the requirements it will be possible to obtain the required results.