Investigation of AC Copper Loss Considering Effect of Field and Armature Excitation on IPMSM With Hairpin Winding

As the torque density of traction motors for electric vehicles (EVs) increases, winding technology with a large conductor area, such as hairpin winding, is widely used. However, it has a disadvantage of large AC copper loss affected by the skin and proximity effect. Therefore, the AC copper loss should be considered for deriving characteristics of interior permanent magnet synchronous motors (IPMSMs). This article deals with the maximum torque per ampere (MTPA) and flux-weakening control characteristics of the IPMSM considering AC copper loss. As the AC copper loss is caused by armature and field excitation, a separation process of AC copper loss by each cause is proposed. By using the process, the separated AC copper loss can be analyzed according to the current vector and rotational speed. However, it is inefficient to calculate the AC copper loss according to rotational speed using transient analysis. Therefore, a computationally efficient method of calculating AC copper loss based on magneto-static analysis is presented. In addition, advanced d, q-axis equivalent model considering AC copper loss is proposed to analyze MTPA and flux-weakening control characteristics of IPMSM. By using the proposed d, q-axis equivalent model, the IPMSM can be designed considering the AC copper loss efficiently and accurately.