• The Transactions of the Korean Institute of Power Electronics
• /
• v.3 no.1
• /
• pp.46-52
• /
• 1998

This paper describes a current-shaping method for the production of constant torque of SRM under the nonlinear magnetic saturation condition. A current detection technique in the inductance increasing region and an approximation technique for modeling of nonlinear inductance profile are adopted. In the proposed system, a single switching angle control and voltage control is used to shape the current waveform for the generation of flat torque at any given load condition. Finally the validity of the proposed method was verified using a constructed 3HP 6/4 SRM.

• Proceedings of the KIPE Conference
• /
• 2002.11a
• /
• pp.21-24
• /
• 2002

The vector control system of an induction motor is the high performance drive system to achieve the instantaneous torque control. The vector control system is greatly divided into the direct control, and the indirect control that the most widely is used, The indirect vector control needs the rotor time constant, which changes widely according to the temperature, frequency, and current amplitude. The incorrect time constant leads to the saturation of magnetic flux or under-excitation phenomena. As a result, that deteriorate the control performance. Therefore, in this paper, the effect of time constant variation is investigated and its on-line tuning algorithm is proposed. The time constant using the torque angles was calculated and that of the validity of algorithm proposed was proved through the computer simulation and the experiment.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.14 no.4
• /
• pp.268-277
• /
• 2009

This paper presents an DTC-PWM (Direct Torque Control-Pulse Width Modulation) of PMSM (Permanent Magnet Synchronous Motor). The proposed DTC-PWM method combines a conventional DTC and PWM approach for switching signal generation. The actual torque is estimated by the torque estimator in conventional method, but the switching signal is generated by PWM method according to the switching rules and torque error. A effective voltage vector and zero vector are used to generate the switching signals and asymmetric switching method is applied. A simple calculation of PWM without any complex determination of space vector can assure the constant switching frequency with an constant torque and flux. The proposed torque control scheme for PMSM is verified by experimental results.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.55 no.1
• /
• pp.9-15
• /
• 2006

The conventional hysterysis band DTC(Direct Torque Control) strategy have relatively high torque ripple at low speed and variable switching frequency according to motor speed even though it provides a fast torque response with very simple scheme consisted with only two hysteresis band comparators and a switching table for torque and flux control. In this paper, author proposed a new DTC scheme based on the torque slope and reference voltage control. The new scheme can maintain the minimized torque ripple and constant switching frequency. Experimental tests carried out with an 1.5kW induction motor drive system show improved dynamic characteristics and prove the feasibility of proposed strategy.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.52 no.1
• /
• pp.1-8
• /
• 2003

The paper proposes instantaneous torque control of IPMSM for maximum torque drive of torque and current plane. The control scheme is based on the mathematical model of the motor and is applicable to the constant torque and field weakening operations. The scheme allows the motor to be driven with maximum torque per ampere(MTPA) characteristic below base speed and it maintains the maximum voltage limit of the motor wide field weakening and the motor current limit under all conditions of operation accurately. For each control mode, a condition that determines the optimal d-axis current $^id$ for maximum torque operation is derived. The proposed control algorithm is applied to IPMSM drive system for drive of wide speed range, the operating characteristics controlled that maximum torque control are examined in detail by simulation.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.50 no.1
• /
• pp.23-29
• /
• 2001

A BLDC motor has a serious drawback that torque pulsation is generated in every commutation period though it has many advatages compared to the conventional DC Motor. In this paper, the influence of commutation time on torque pulsation is studied. Generally in calculating the torque of BLDC motor, it is assumed that the decaying phase back EMF is constant, but the torque model considering decaying phase back EMF is introduced here. Through it, the torque in commutation period has torque pulsation component caused by commutation itself and it cannot be removed perfectly even if there is no current pulsation. To reduce the torque pulsation, a new method is proposed, which controls a point of commutation and the optimal point of commutation is found. Simulation shows that proposed method reduces the torque pulsation considerately.

• Proceedings of the KIPE Conference
• /
• 2007.11a
• /
• pp.148-150
• /
• 2007

A novel torque sharing function (TSF) is presented. To improve efficiency and to reduce torque ripple in commutation region, only a phase torque under commutation is regulated to produce a uniform torque. And the torque developed by the other phase remains with the previous state under a current limit of the motor and drive. If the minimum change of a phase torque reference can not satisfy the total reference torque, two-phase changing mode is used. Since a phase torque is constant and the other phase torque is changed at each rotor position, total torque error can be reduced within a phase torque error limit. And the total torque error is dependent on the change of phase torque. To consider non-linear torque characteristics and to suppress a tail current at the end of commutation region, the incoming phase current is changed to torque increasing direction, but the outgoing phase current is changed to torque decreasing direction. So, the torque sharing of the outgoing phase and incoming phase can be smoothly changed with a minimum current cross over. The proposed control scheme is verified by some computer simulations and experimental results.

• Proceedings of the KIEE Conference
• /
• 2007.10c
• /
• pp.138-140
• /
• 2007

A novel non-linear logical torque sharing function (TSF) is presented. To improve efficiency and to reduce torque ripple in commutation region, only a phase torque under commutation is regulated to produce a uniform torque. And the torque developed by the other phase remains with the previous state under a current limit of the motor and drive. If the minimum change of a phase torque reference can not satisfy the total reference torque, two-phase changing mode is used. Since a phase torque is constant and the other phase torque is changed at each rotor position, total torque error can be reduced within a phase torque error limit. And the total torque error is dependent on the change of phase torque. To consider non-linear torque characteristics and to suppress a tail current at the end of commutation region, the incoming phase current is changed to torque increasing direction, but the outgoing phase current is changed to torque decreasing direction. So, the torque sharing of the outgoing phase and incoming phase can be smoothly changed with a minimum current cross over. The proposed control scheme is verified by some computer simulations and experimental results.

• Proceedings of the KIEE Conference
• /
• 1994.07a
• /
• pp.298-302
• /
• 1994

Brushless DC motors have a trapezoidal back EMF wave form and are fed with rectangular stator currents. Under these conditions, the torque produced is theoretcally constant. However, in practice, torque ripple may exist, one major cause of which conies from phase current commutation. In this paper we propose an improved method of reducing the torque ripple due to phase current commutation of indirectly restricting the uncommutated current through control of the other phase currents. Simulation results are present.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.4 no.2
• /
• pp.201-208
• /
• 1999

This paper presents the degradation of the system performance according to the vmiation of the rotor time constant. The algorithm for the on-line estimation of rotor time constant is proposed. which is applied to the consistent relationship between the tangent torque angle of the synchronous reference frame and that of stationary reference f frame. For the purpose of the validity of proposed algorithm. the computer simulation and the experiments have been p performed.