Byung-il Kwon

Commutation Torque Ripple Reduction in a Position Sensorless Brushless DC Motor Drive

This paper presents a novel method to reduce commutation torque ripple in a position sensorless brushless DC (BLDC) motor drive. To compensate the commutation torque ripple completely, conventional methods should know commutation interval, so that they need current sensors. However, the proposed method measures commutation interval from the terminal voltage of a brushless DC motor, calculates a PWM duty ratio using the measured commutation interval to suppress the commutation torque ripple, and applies to the calculated PWM duty ratio only during the next commutation. Experimental results verify that the proposed method implemented in an air-conditioner compressor controller considerably reduces not only the pulsating currents but also vibrations of a position-sensorless BLDC motor.

A Novel Starting Method of the Surface Permanent-Magnet BLDC Motors Without Position Sensor for Reciprocating Compressor

This paper describes a new position sensorless starting method, specialized for low-cost applications, of a brushless dc (BLDC) motor with a surface permanent-magnet (SPM) rotor to prevent demagnetization of permanent magnet and vibrations due to pulsating currents during the starting period. That the magnitude of peak current causes irreversible demagnetization of permanent magnet, has been measured through experimental tests. The proposed method limits the motor currents during the starting period to lower than the demagnetization currents by doing commutation depending on the level of the measured phase currents. Experimental results show that the proposed method implemented in an inverter for a BLDC motor-driven reciprocating compressor considerably reduces not only the pulsating currents but also the vibration of the compressor during starting.

Rotor Pole Design in Spoke-Type Brushless DC Motor by Response Surface Method

This paper proposes a novel rotor pole shape which consists of a uniform surface and an eccentric surface to make a sinusoidal magnetic flux density in air gap in order to reduce cogging torque, torque ripple, and harmonics of back-electromotive force waveform in spoke-type brushless DC motor. In the process of design and analysis, response surface methodology and the 2-D finite-element method are employed to obtain the rotor geometry and verify the results of the novel rotor pole shape

A Novel Dual-Stator Axial-Flux Spoke-Type Permanent Magnet Vernier Machine for Direct-Drive Applications

This paper proposes a novel double-stator axial-flux spoke-type permanent magnet vernier machine, which has a high torque density feature as well as a high-power factor at low speed for direct-drive systems. The operation principle and basic design procedure of the proposed machine are presented and discussed. The 3-D finite element method (3-D-FEM) is utilized to analyze its magnetic field and transient output performance. Furthermore, the analytical method and a simplified 2-D-FEM are also developed for the machine basic design and performance evaluation, which can effectively reduce the modeling and simulation time of the 3-D-FEM and achieve an adequate accuracy.

Material-Efficient Permanent-Magnet Shape for Torque Pulsation Minimization in SPM Motors for Automotive Applications

This paper focuses on the design and analysis of a novel material-efficient permanent-magnet (PM) shape for surface-mounted PM (SPM) motors used in automotive actuators. Most of such applications require smooth torque with minimum pulsation for an accurate position control. The proposed PM shape is designed to be sinusoidal and symmetrical in the axial direction for minimizing the amount of rare earth magnets as well as for providing balanced axial electromagnetic force, which turns out to obtain better sinusoidal electromotive force, less cogging torque, and, consequently, smooth electromagnetic torque. The contribution of the novel PM shape to motor characteristics is first estimated by 3-D finite-element method, and all of the simulation results are compared with those of SPM motors with two conventional arched PM shapes: one previously reported sinusoidal PM shape and one step skewed PM shape. Finally, some finite-element analysis results are confirmed by experimental results.

A Study on Optimal Pole Design of Spoke-Type IPMSM With Concentrated Winding for Reducing the Torque Ripple by Experiment Design Method

An optimal design procedure is proposed to effectively reduce the torque ripple by optimizing the rotor pole shape of the spoke-type IPMSM with concentrated winding. The procedure is composed of two steps. In step 1, the steepest descent method (SDM) is used with only two design variables to rapidly approach the optimal shape. From the near optimal rotor shape as a result of the step 1, the design variables are reselected, and the drawing spline curves are utilized to explain more complex shape with the Kriging model in step 2. By using an optimal design procedure, we show that the optimized rotor pole shape of the spoke-type IPMSM effectively reduces the torque ripple while still maintaining the average torque.

Finite element analysis of direct thrust-controlled linear induction motor

This paper describes the finite element analysis of a direct thrust-controlled linear induction motor (LIM). The time-stepping finite element method and the moving mesh technique are used to calculate the dynamic characteristics of the LIM during direct thrust control. Because the LIM has an end effect, a thrust correction coefficient is introduced to predict actual thrust in control. The simulation results, the thrust and the stator flux linkage are shown and the stator current is compared experiments.

Comparative Study on Novel Dual Stator Radial Flux and Axial Flux Permanent Magnet Motors With Ferrite Magnets for Traction Application

This paper proposes two novel traction motors with ferrite magnets for hybrid electric vehicles (HEVs), which have competitive torque density and efficiency as well as operating range with respect to a referenced rare earth magnet motor employed in the third-generation Toyota Prius, a commercialized HEV. The two proposed traction motors, named as dual stator radial flux permanent magnet motor (DSRFPMM) and dual stator axial flux permanent magnet motor (DSAFPMM), adopt the same design concept, which incorporates the unaligned arrangement of two stators together with the use of spoke-type magnet array and phase-group concentrated-coil windings for the purpose of increasing torque density and reducing torque ripple. A finite element method is utilized for predicting the main characteristics, such as back electromotive force, cogging torque, electromagnetic torque, iron loss, and efficiency in both of the proposed motors. Moreover, a comparative study between the proposed DSRFPMM and DSAFPMM is performed under the same operating condition. As a result, it is demonstrated that both of the proposed ferrite permanent magnet motors could be good alternatives for traction application, replacing the rare earth magnet motors.

Novel topology of unequal air gap in a single-phase brushless DC motor

Most single-phase brushless DC (BLDC) motors have unequal air gaps to eliminate the dead point where the developed torque value is zero. These unequal air gaps deteriorate the motor characteristics in cogging torque. Thus in this paper a new topology of the unequal air gaps is proposed to solve this problem. As a result, it is proved by the finite element analysis and experimental results that the proposed air gap topology is very effective in reducing the cogging torque.

Optimization of Two-Phase In-Wheel IPMSM for Wide Speed Range by Using the Kriging Model Based on Latin Hypercube Sampling

This paper introduces an optimal design process for in-wheel interior permanent magnet synchronous motor (IPMSM) to achieve wide speed range. A finite element method (FEM) was used for calculating the inductances of the d-axis and q-axis by changing the structure of rotor shape in IPMSM. After FEM analysis, optimal design process to find optimal rotor shape is processed for wide speed range. In optimal process, the Kriging method based on the Latin hypercube sampling (LHS) and a genetic algorithm (GA) are applied due to suitability to non-linear data. Using this optimal design process, an optimal rotor shape is obtained. The optimal model has an increased wide speed range with reduced cogging torque.