Studies on the influence of manufacturing processes on the eddy current losses of single-tooth stator lamination stacks for use in hybrid and electric drives

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Due to societal and political demand for environmental-friendly and sustainable automotive technology, the industry is facing requests to develop new powertrain concepts. Many of the powertrain concepts are based on a drive system with electric motors. This can be a full electric vehicle with a large battery, a hybrid vehicle or a fuel cell vehicle. All concepts do have, as a common main powertrain component, an electric motor. The reduction of the power loss of the electric motor is one major focus of the development activities. The power loss has straight impact to the compliance with the CO2 emission regulations, the operating range of the electric vehicle, the cost and weight of the battery and the cooling power demand of the system. For this reason the entire types of power losses have to be investigated fundamentally, power loss reduction potentials have to be identified and improvements have to be established and implemented.One type of losses is the eddy current losses. The eddy current losses are mainly generated in the laminations of the iron cores of the electric motor. For eddy current loss minimisation the individual laminations of the stack are electrically insulated. However the application of manufacturing processes can lead to electrical connections of the laminated, initially insulated stack and will therefore lead to additional eddy current losses. The impact of the manufacturing processes concerning additional eddy current losses is currently not sufficiently known.A major component of the electric motor is the laminated stator core. The manufacturing process steps, cutting of the individual lamination, stacking of the laminations to a core and the assembly of the stator core in a housing differ concerning their eddy current loss impact. The main target of the presented research project is therefore the determination of the eddy current losses created through the impact of various manufacturing processes. For this purpose, the eddy current paths caused by the manufacturing processes have to be identified and the relevant geometrical and electrical dimensions have to be detected. In a next step FEM simulations have to be carried out and based on the found eddy current characteristics analytical calculation models can be developed. Finally, the simulation and calculation results have to be validated by measurements.Based on the identified eddy current characteristics requirements for loss minimisation of the applied processes and the part quality can be specified. In addition a guide line for the design of stator cores with the focus on loss reduction can be offered. Further the results of the investigations will be the basis for the determination of additional manufacturing processes for loss reduction e.g. the insertion of insulation layers at certain locations to disconnect eddy current paths. In a last step the identified loss reduction actions have to be evaluated concerning their effectiveness by measurements.