• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.227-229
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• 1997

The torque of SRM is developed by phase currents and inductance variation. The inductance of torque generation region is nonlinearly varied according to phase current. By this nonlinear characteristics, torque ripple can be generated on the condition of constant current. Otherwise, phase current should be controlled instantaneously in accordance with inductance to reduce torque ripple. In this paper, the control system with neural network that can reduce torque ripple is suggested. In this control system, instantaneous inductance and optimal current waveform for smallest torque ripple is obtained by neural network. And this required optimal current waveform is regulated by voltage control.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.142-145
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• 2001

In this paper the electromagnetic torque developed in IPMSM(Interior Permanent Magnet Synchronous Motor) is analyzed. If flux distributions in the motor are not sinusoidal, a sinusoidal current produces important torque ripple. Torque ripple causes vibration and noise of motors. The optimized current waveforms for ripple free is able to be obtained by analysis of Back-EMF and torque equation. The method to find the optimal current is based on numerical predetermination. In this paper proposes current waveform which can eliminate the torque ripple, and the validity is verified through the simulation.

• Journal of Power Electronics
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• v.11 no.2
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• pp.148-155
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• 2011

Direct torque control(DTC) of induction machines is known to offer fast instantaneous torque and flux control with a simple control structure. However, this scheme has two major disadvantageous, namely, a variable inverter switching frequency and a high torque ripple. These problems occur due to the use of hysteresis comparators in conventional DTC schemes, particularly in controlling the output torque. This paper reviews the utilization of constant frequency torque controllers (CFTC) in DTC to solve these problems while retaining the simple control structure of DTC. Some extensions of the work in utilizing a CFTC will be carried out in this paper which can further reduce the torque ripple. This is particularly useful for a system which has a limited/low sampling frequency. The feasibility of a CFTC with an extended carrier frequency in minimizing the torque ripple is verified through experimental results.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.6
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• pp.620-631
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• 2000

A torque ripple reduction technique of direct torque control(DTC) for high power induction motors driven by 3-level inverters with the inverter switching frequency limited around 0.5-1.0kHz level is presented. It is noted that conventional DTC algorithms to reduce torque ripple are devised for applications with relatively high switching frequency above 2-3kHz. Such conventional algorithms can not accomplish satisfactory torque ripple reduction for 3-level inverter systems with lower switching frequency. A new DTC algorithm, especially for low switching frequency inverter system, illustrates relatively reduced torque ripple characteristics all over the operating speed region. Simulation and experimental results show the effectiveness of the proposed control algorithm.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.9
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• pp.530-536
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• 2002

In this paper, a new torque ripple compensator is proposed. The proposed torque ripple compensator utilizes only speed information, so it can be easily applied to an existing motor drive system by including the algorithm. The stability analysis is discussed. From the discussion, the proper gain selection method, which makes the compensator stable and fast convergent, is also presented. The experimental results are presented and show the torque ripple reduction capability of the proposed scheme.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.580-582
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• 2002

A major problems of Switched Reluctance Motor(SRM) is torque ripple which causes undesirable acoustic noise and vibration. To reduce the torque ripple two different approaches are used. One is to modify a motor geometry, the other is to manipulate motor current to improve performance. This paper presents modifications of the rotor pole shape which reduces the torque ripple.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.337-341
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• 1998

Brushless DC motors have trapezoidal back emf waveform. Generally, because it is drived by a voltage source inverter, the ideal rectangular phase current is not available and therefore produce torque ripple. In this paper, the torque ripple due to commutation is analysed and the practical method that can reduce the torque ripple is proposed. Simulation and experimental results show the effectiveness of the proposed method.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.342-346
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• 1998

The brushless DC motor with trapezoidal back emfs has torque ripple due to phase commutation. The torque ripple generates noise and vibration and cause errors in position control so this makes the brushless DC motor less suitable for high performance servo applications. In this paper, we propose a new current control method to reduce the torque ripple due to commutation, when the unipolar PWM method is applied for the phase current control of brushless DC motor.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2289-2297
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• 2017

Applying a periodic load torque to an AC motor generates a ripple, which is synchronized to the frequency of the periodic load torque, at the speed of the motor. Consequently, numerous studies have focused on reducing the speed ripple caused by the load torque. However, it is difficult to reduce the speed ripple when there is a time delay in acquiring speed information, such as that from a sensorless control. Therefore, we propose a speed control method for reducing speed ripples caused by a periodic load torque when there is a time delay in acquiring the speed information. The proposed method is verified by conducting simulations using the Simulink program from MATLAB, and by applying the method to an actual motor in which speed ripples occur due to a periodic load torque that is synchronized with the speed of the motor.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.203-206
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• 2000

This paper presents a torque ripple reduction technique of direct torque control(DTC) for high power induction motors driven by 3-level inverters with the inverter switching frequency limited around 0.5-1kHz level. It is noted that conventional DTC algorithms to reduce torque ripple are devised for applications with relatively high switching frequency above 2-3kHz. A new DTC algorithms especially for low switching frequency inverter system illustrates relatively reduced torque ripple are devised for applications with relatively high switching frequency above 2-3kHz. Anew DTC algorithm especially for low switching frequency inverter system illustrates relatively reduced torque ripple characteristics Simulation and experimental results show the effectiveness of the proposed control algorithm