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While the electromagnetic aspects of hairpin windings are actively being investigated and discussed in recent literature, including the design rules together with the loss calculation and reduction techniques, the thermal performance and modeling aspects have received less attention to date. In hairpin windings, the conductors (pins) are comparatively larger and arranged as separate components in parallel within the slot. In contrast, conductors randomly overlap and contact each other for traditional random windings. The differences in the aforementioned winding physical characteristics result into a different methodology to develop the thermal network. This paper presents a 3D Lumped Parameter Thermal Network (LPTN) approach for an oil-spray cooled hairpin winding, which includes the slot thermal model configuration, the end-winding connections, together with different methodologies of analyzing the end-winding sprayed-oil characteristics. The aforesaid thermal model captures unique features related to the winding technology and cooling mechanism, such as the non-uniform endwinding temperature caused by the uneven oil spray cooling effects. Finally, taking an existing propulsion drive hairpin stator and a bespoke-designed test setup, the presented steady state thermal modelling approach is experimentally validated covering various experimental tests, including different spray conditions.

This paper presents a comparison between hairpin and random distributed winding in electrical machines for automotive applications. Indeed, the overall performance of an electrical drive system is seriously affected by its winding design. The considered electrical machine has a peak power of 115kW and a maximum operating speed of 12000 rpm. Both cost and manufacturing aspects are here discussed in detail. Two different machine topologies have been investigated and Finite Element Analysis (FEA) results are presented and discussed. Then, the comparison between hairpin and random winding configuration in terms of AC copper losses are presented for the selected geometry. The accurate AC losses estimation can be done by modelling each single conductor. In order to significantly reduce the simulation time, a domain model reduction has been adopted. Based on two different driving cycles, Urban Dynamometer Driving Schedule (UDDS) and Highway Fuel Economy Test (HWFET), the AC losses have been evaluated. The main outcome of this work is the considerable reduction of AC losses by using a segmented hairpin winding.

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In motor drive system, the inverter working in discrete and impulse state generate the common mode voltage (CMV) in the terminal of stator winding neutral point. The high frequency CMV can induce the leakage current and commonmode (CM) electromagnetic interference (EMI) which is a potential threat to personal safety and system stability. The conventional single three-phase inverter is proved powerless to eliminate the CMV, while the two paralleled inverters can effectively eliminate the CMV theoretically, but the three coupled inductors (CIs) should be added in the motor drive system which reduces the power density and efficiency of the system. A novel method which associates the special designed dual-segment three-phase motor with the CMV elimination modulation algorithm can be utilized to cancel the extra CIs without degrading the function of leakage current and CM EMI suppression. Design of the dual-segment three-phase PMSM is introduced, with the identical back-EMFs for two groups of windings but little magnetic coupling between them. Simulation and experimental results are provided to verify the validity of proposed method in CM related reduction and CI cancellation. Compared with previous work of zero-CM PWM for paralleled inverters, the proposed dual-segment three-phase motor drive can achieve better power density by removing the coupled inductors.