Effect of Manufacturing Processes on Electrical Machine’s Performance

Abstract

This thesis focuses on the effects of manufacturing processes on electrical machine performance. The effects of cutting, welding, and shrink fitting are considered and the effects of cutting are studied more thoroughly in this thesis. A 37 kW induction motor is used as a test machine. A cutting loss model is proposed based on Epstein frame measurements of non-oriented strips of different cutting lengths. The loss model is validated with core loss measurements of the strips and stators manufactured with wire electric discharge machining and laser cutting. The proposed cutting loss model is also evaluated with grain-oriented strips cut with punching, water jet and laser cutting. Furthermore, two different finite element approaches based on higher and mixed-order elements are proposed for computationally efficient modelling of the cutting effects. The effect of welding is analysed with measurements of the ring cores of loose and welded sheets of stator laminations. In addition, stator core losses are measured with and without the frame to quantify the shrink fitting effects. Different approaches are proposed to include the effects of welding and shrink fitting in the finite element analysis of an electrical machine. A dummy blocked rotor test setup is designed and manufactured to measure the effect of different manufacturing processes on the stator core losses. As a result of manufacturing processes, the stator core losses of the induction machine increased by 23 % at the rated flux (400 V, 50 Hz). The contributions of cutting, welding, and shrink fitting are observed to be about 10 %, 7 %, and 6 % respectively. The presented loss models are found to predict the corresponding effects of manufacturing processes accurately.