In this article, the electromagnetic force and vibration characteristics of 10-pole 12-slot and 14-pole 12-slot permanent magnet synchronous motors (PMSMs) are examined considering the tooth modulation effect. In contrast to the conventional electromagnetic force analysis process which considers only the radial force of the lowest spatial harmonic order, the radial and tangential forces include low and high spatial harmonic orders which can be modulated with a lower spatial harmonic order, are analyzed. Then, a structural finite-element (FE) model is developed, and vibration analysis is performed by applying a modulated force and moment. In the analysis, the amplitude and phase of the modulated radial force, tangential force, and moment are considered. The vibration analysis result shows that the 10-pole 12-slot PMSM is disadvantageous with respect to vibration when compared to the 14-pole 12-slot PMSM owing to the large modulated force. Also, it is confirmed that the effect of modulated tangential force and moment cannot be neglected, and the phase difference between modulated radial, tangential force and moment is also an important factor in vibration. Finally, the two motors are fabricated, and the validity of the FE analysis results is verified using the test results.

Electric vehicle (EV) systems require a high energy-efficiency traction motor so that the motors for EV traction should achieve high efficiency and power density. Hence, a permanent magnet synchronous motor (PMSM) for EV traction using a maximum slot occupation (MSO) coil has been investigated in this study. By applying the MSO coil, high torque density was achieved, but an additional loss, which decreases the efficiency, was incurred through alternating current (AC) resistance. To reduce the AC resistance of the MSO coil, the following process was performed: First, by investigation using the analytical method, pole/slot numbers, current density and number of parallel circuits affecting the frequency, the shape and number of conductors were chosen as important variables. Resistances of the MSO coil with a stator core were analyzed according to the chosen variables above. From the results, MSO coil applied PMSM with proper pole/slot numbers, current density, and parallel circuits was determined to improve the efficiencies at the base and maximum speeds. To accurately estimate the efficiency of the determined model, loss evaluation methods were explained. Subsequently, the determined MSO coil applied model was compared with the conventional model having round wires, and the improvements were verified by load testing.

The accuracy of motor characteristics prediction according to driving cycle can be improved by taking temperature change of motor into account. From this point of view, this paper proposes a fast and accurate coupled analysis method. To calculate motor circuit parameters, electromagnetic finite element analysis (FEA) is used. The proposed method consists of two stages to exclude the time consuming FEA from repetitive process. In pre-process stage, the circuit parameters are stored as look-up tables (LUTs) considering motor temperature. Further, a technique that allows reducing the number of analyses is developed to consider a wide operating temperature range with less time consumption. In main process stage, the torque and voltage equations are solved using the circuit parameter LUTs. Among the solved motor characteristics, losses are applied to lumped parameter thermal network (LPTN) as heat sources to figure out thermal characteristics. Here, techniques including loss separation and thermal parameter tuning are introduced to improve both accuracy and speed of the LPTN. Since the computation of the characteristic equations and LPTN are fast, the iterative analysis at entire time steps of the driving cycle is facilitated. An example of the proposed method is presented using worldwide harmonized light vehicle test procedure (WLTP). Thereafter, the effectiveness of the method is discussed by comparison with conventional methods. Finally, the experimental verifications are conducted to validate the electromagnetic FEA and LPTN used in this study.

The propulsion system of the electric-powered vertical take-off and landing aircraft requires a high level of performances, including power density, efficiency, noise vibration and harshness, and fault tolerance. Among many types of conventional electric motor, the outer rotor surface-mounted permanent magnet synchronous motor (SPMSM) is widely used for its high power density and low torque pulsation. However, these advantages are degraded when the multiphase winding is applied to secure the fault-tolerance characteristics. To overcome the limit of conventional motor topology, the dual stator permanent magnet synchronous motor with separately controlled dual three-phase winding is proposed. The advantages of the proposed topology are resulted from the feature of mechanical, electrical, and magnetic isolation. To maximize the distinctive feature, a design process considering separated current vector control (SCVC) method is established. A design example is presented to demonstrate the impacts of the proposed design process considering SCVC on the power density maximization, torque harmonic reduction, and efficiency improvement. Finally, the experimental verification is presented to validate the proposed design and control techniques.

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.

This paper proposes an indirect method for predicting mechanical loss by considering the eddy current loss of permanent magnets (PMs) and conductors under the no-load condition. The mechanical loss has been conventionally predicted indirectly through experiments and numerical methods. The conventional method uses the no-load loss measured through experiments and the no-load iron loss calculated through a numerical method. With the increase in the demand for high power density motors, the PMs with high energy density and winding technology with high fill-factor are required. Thus, the proportion of eddy current losses of PMs and conductors is increasing among the electromagnetic losses. Therefore, we propose an indirect method for predicting the mechanical loss considering the eddy current losses. The accuracy of the proposed method is higher than that of the conventional method. Moreover, the proposed method is verified by comparing the estimated efficiency of the specimen obtained by using this method with the measured efficiency.