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Impact of slit configurations on eddy current and Joule losses in PCB windings of PM machines

Applied to the production of windings, the PCB technology is promising for developing high performance slotless permanent magnet machines, since it makes possible to envisage winding shapes and topologies difficult or impossible to achieve by the classical wire technology. However, compared to wire windings, PCB windings are more subject to eddy current losses because of their high width-thickness ratio. To counteract these eddy currents, the conventional solution consists in reducing the track width but in conjunction with an increased number of turns. That requires, in order to keep the supply voltage constant, to consider parallel connections of conductive tracks at the winding terminals. This paper tackles the eddy current problem differently by adding some slits distributed along the conductive tracks. This amounts to carry out local parallelizations without impacting the motor supply voltage. This study, through a parametric analysis of different slitting possibilities in wave windings, shows that reconnect parallel sub-tracks at one end-winding of two delivers nearly the same results than a classical full parallelization but with a potential simplification of the interconnections between the PCB tracks constituting the winding. Furthermore, it shows that this conclusion is independent of the winding shape considered.