Myung-Seop Lim

Design and Verification of 150-krpm PMSM Based on Experiment Results of Prototype

This paper proposes the design process of a 2.62-kW 150-krpm high-speed surface-mounted permanent-magnet synchronous motor. To meet the required specifications, the numbers of poles and slots were determined by considering the maximum speed and the rotary stability affected by the vibration of the rotor. In addition, this paper describes not only the appropriate material selection method but also the appropriate geometry design method based on analytic approaches. Furthermore, to precisely evaluate the bearing and windage losses at a high speed, a method that combines the finite-element method and the experiment results of the prototype was used. As a result, an improved motor was designed, which had higher maximum power and speed than the prototype and a lower mass moment of inertia. Finally, tests were conducted to verify the validity of the proposed design process and the effectiveness of the motor.

Design of Saliency-Based Sensorless-Controlled IPMSM With Concentrated Winding for EV Traction

This paper investigates the influence of the geometry design parameters of an interior permanent magnet synchronous motor with concentrated winding on the saliency-based sensorless drive feasibility. To evaluate the sensorless controllability of the motors, two different methods to estimate the rotor position error are proposed. By using the methods, the geometry design parameters in the stator are analyzed to figure out which ones have a positive effect on the sensorless drive. The analysis results show that the configuration of the tooth tip is one of the major factors in reducing the estimation error. Based on the results, an optimum design parameter is selected considering both the drive feasibility and the back electromotive force. Last, a final model is proposed and manufactured for electric vehicle traction. The validity of the proposed estimation methods and the design result are verified by the experiments.

Torque Ripple Reduction of IPMSM Applying Asymmetric Rotor Shape Under Certain Load Condition

This paper proposes a new numerical formula and a design method to reduce the torque ripple while improving efficiency and the control performance of an interior permanent magnet synchronous motor. In previous studies, the inverse cosine function (ICF) has been used for torque ripple reduction by making the air gap flux density distribution sinusoidal under a no-load condition. However, in this paper, the advanced inverse cosine function (AICF) based on the ICF is proposed. It determines an asymmetric rotor shape for rendering the air gap flux density distribution sinusoidal, considering a certain load condition. In addition to the torque ripple reduction, lower peak values, the total harmonic distortion (THD) of the induced voltage, and a lower iron loss can be achieved by applying the AICF, compared to the other conventional methods. The lower peak value and THD of the induced voltage are important because they affect the control performance of the motor. The lower iron loss can also lead to a higher efficiency, particularly, in the high-speed region. To verify the validity of the proposed design method, the characteristics of 8-pole, 12-slot motors that have different rotor shapes are analyzed using finite element analysis and experiments.

Design of sensorless controlled IPMSM with concentrated winding for EV drive at low speed

The sensorless control based on the high frequency voltage signal injection method is typically used for detecting the rotor position of an interior permanent magnet synchronous motor (IPMSM). This technique is essential at zero and low speed operating region, where back electromotive force is extremely low. The sensorless-oriented machines require the same minimum value positions of the d-axis self-inductances, regardless of the rotor position. It means that the zero-crossing points of the dq-axis mutual-inductances varied with the rotor position should be constant as well. This paper introduces the design procedure of a saliency-based sensorless controlled concentrated winding IPMSM for vehicle traction, fulfilling the requirements mentioned above. The evaluating process of the sensorless drive feasibility by using finite element analysis (FEA) is proposed, with taking account of cross-coupling effect and saturation. Utilizing the evaluating method, some geometry design parameters are examined to figure out which ones have a positive effect on detecting the rotor position. Based on the influences of the parameters on the dr i ve feasibility, the design conditions for the sensorless drive concentrated winding IPMSM are determined. Finally, the proposed model applied with the geometry design conditions and the FEA results are shown. It is found that accuracy of the rotor position estimation is improved by means of the proper geometry design of the machines.

Design of an Ultra-High-Speed Permanent-Magnet Motor for an Electric Turbocharger Considering Speed Response Characteristics

This paper presents a design methodology and analysis for a 4-kW 150-krpm ultra-high-speed surface-mounted permanent-magnet synchronous motor (SPMSM) to electrically assist a turbocharger. The proposed design methodology is aimed at achieving a required torque and speed. In addition, this study seeks a fast-speed response as a design objective to eliminate turbo lag more effectively. First, an existing prototype that does not meet the target performance is presented. The loss for the prototype, which is difficult to obtain theoretically, is obtained experimentally and reflected in the design. The speed response characteristic of the machine is analyzed through the electromechanical undamped natural frequency and damping ratio. Design parameters such as the permanent-magnet (PM) grade, the turn number of coils, and the axial length of the motor are designed. The resulting improved motor achieves higher power density as well as faster speed response than the prototype. Experiments verified the effectiveness of the motor in the electrically assisted turbocharger. In system experiments with the turbocharger, the rising speed of the boost pressure is improved by 44.9% due to the designed motor.

Hysteresis Torque Estimation Method Based on Iron-Loss Analysis for Permanent Magnet Synchronous Motor

In the design process of permanent magnet synchronous motors (PMSMs), the hysteresis torque has so far been ignored under the understanding that it is already small enough. However, for some delicate applications, such as an exoskeleton wearable robot, the hysteresis torque, whose proportion increases under no-load or low-load conditions, needs to be further minimized even though the hysteresis torque has low magnitude. Conventional methods using hysteresis models to calculate the hysteresis torque require a lot of computation resources. Therefore, this paper proposes a simpler method in order to estimate the hysteresis torque using iron-loss experimental data. In the proposed method, the hysteresis torque is derived from the hysteresis loss, which is separated from the iron-loss experimental data by using the modified Steinmetz equation. Finally, the hysteresis torque of the proposed surface-mounted PMSM is measured via experiments to verify the validity of the proposed method. The hysteresis torque is obtained by subtracting the mechanical friction torque from the no-load offset torque. The experimental result is compared with the results obtained from the proposed method.

Experimental Characterization of the Slinky-Laminated Core and Iron Loss Analysis of Electrical Machine

The magnetic properties of a motor core deteriorate during the manufacturing process due to mechanical stresses in the materials. It is particularly hard to predict the characteristics of the slinky-laminated electrical machines, because stresses and strains occur simultaneously in the core. To examine the B-H curve and the iron loss of a core affected by the manufacturing process, a slinky-laminated surface-mounted permanent magnet synchronous motor (SPMSM) was proposed as an analysis model. The magnetic properties of the slinky-laminated core and the stacked core were compared as the results of material experiments, using the proposed motor core. With the examined material data, the iron loss of the slinky-laminated SPMSM was investigated via the finite-element method (FEM). Finally, the proposed motor was subjected to a no-load test and a mechanical loss test. Based on the test results, the actual iron loss of the motor was obtained through loss segregation and was then compared with the FEM results to verify the validity of the material experiment and loss analysis methods.