• Journal of Power Electronics
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• v.9 no.2
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• pp.232-242
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• 2009

In this paper, a matrix converter with improved low frequency output performance is proposed by achieving a one-step commutation owing to a general commutation circuit applicable to n-phase to m-phase matrix converters. The commutation circuit consists of simple resister and capacitor components, leading to a very stable, reliable and robust operation. Also, it requires no extra sensing information to achieve commutation, allowing for a one-step commutation like a conventional dead time commutation. With the dead time commutation strategy applied, the distortion caused by commutation delay is analyzed and compensated, therefore leading to better output linear behavior. In this paper, detailed commutation procedures of the R-C commutation circuit are analyzed. A selection of specific semiconductor switches and commutation circuit components is also provided. Finally, the effectiveness of the proposed commutation method is verified through a two-phase to single-phase matrix converter and the feasibility of the compensation approach is shown by an open loop space vector modulated three-phase matrix converter with a passive load.

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

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.1
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• pp.57-62
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• 2013

Because of high torque and easiness of speed control, Direct Current(DC) motors have been used for a long time. But, its applications are limited in circumstance and performance, since they contained brush and commutator. The commutation characteristic gives effect to life and performance of the DC motor. Naturally, the commutation characteristic analysis is strongly required. In this paper, With the result of finite element analysis, The inductance is calculated each rotor position and applied to the voltage equations coupled with commutation equation. Also, contact resistances of brush/commutator assembly are considered using contact area and brush width converted with commutator segments. The time derivative term in the differential equation is solved in time difference method. This algorithm was applied to 2-pole shunt DC motor. We considered commutation characteristic by changing contact resistance between brush and commutator segment.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.610-614
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• 2000

Torque pulsation generated in every commutation period is the main drawback of BLDC motor which deteriorates the precision of BLDC motor. Many methods to solve this problem have been proposed. In this paper a new torque model considered with decaying phase back EMF is introduced and from it the cause of torque pulsation in commutation period is analyzed. Form this analysis new algorithms to reduce the torque pulsation by commutation time are proposed and with simulation the validity is verified.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.6
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• pp.927-935
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• 1994

Detailed analysis of the commutation circuit of the proposed wide-frequency current source inverter is given. In this inverter a spike-limit circuit and a precommutation circuit are used. The spike-limit circuit is intended to limit spike voltage which is arising during commutation time in a current source inverter, and the precommutation circuit to reuse the energy which flows from main inverter to spike-limit circuit during commutation time to aid commutation. Thus voltage stress of main thyristor is minimized. Since this inverter can be made up of thyristors for phase control, it has some advantage in high voltage and high power application.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.641-643
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• 2000

Because of high torque and easiness of speed control, Direct Current(DC) motors are used long time. But, its applications are limited in circumstance and performance, since they contained brush and commutator. The commutation characteristic gives effect to life and performance of DC motor. Naturally, the commutation characteristic analysis is strongly required. In this paper, With the result of finite element analysis. The inductance is calculated each rotor position and applied to the voltage equations coupled with commutation equation. The time derivative term in the differential equation is solved in time difference method. This algorithm was applied to 2-pole shunt DC motor. We considered commutation characteristic by changing contact resistance between brush and commutator segment.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.1
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• pp.56-63
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• 2003

This paper studies that torque model considered with decaying phase back-EMF is different In conduction and commutation period and analyzes the torque pulsation components mathematically. In this paper, it is proposed a novel method to suppress torque pulsation due to commutation time. First, it propose commutation delay time control method, which is to compensate current slope of rising phase and decaying phase to control commutation time. Current ripple is minimized at non-commutating current and torque ripple is reduced below critical speed range that dc link voltage is the same as four times of back-EMF voltage. However, torque ripple still exists due to the relation with back-EMF and commutating current and it is increased on a large scale above critical speed range, especially. Secondly, proposed method is commutation time control, which is considered with torque pulsation due to the relation of back-EMF and commutating current. Through the proposed method, the torque pulsation can be minimized in the whole speed range as well as range over critical speed.

• Journal of Advanced Marine Engineering and Technology
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• v.9 no.3
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• pp.250-256
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• 1985

With the advant of thryistors having large peak inverse voltages, current-source inverters are becoming very popular to feed induction motors. But it is very difficult to analysis the commutation. Since the actual variation of current during commutation is neither instantaneous nor linear and is effected by many parameters. Minimized bias-time of reverse voltages during commutation is expressed in term of machine parameters, capacitor voltage, load current and so on. The minimized bias-time is computed with y and z and also the commuation mechanism is tested on 2.2 kw induction motor. The computed results are compared with the experimental results, and the results give a good information for designing the commutation mechanism.

• 전기의세계
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• v.17 no.2
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• pp.6-10
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• 1968

The conversive limitation of electric energy for the thyristor inverter is analysed under the boundary conditions which the term of a negative inverse voltage is longer than that of the turn off time of the thyristor under commutation. It is clear that the maximum electric energy conversion is affected by the turn off time of the thyristor, the reactance of a commutation reactor, the capacity of a commutation condenser and the voltage of Direct current source. It is useful for design the thyrister invertor and the motor speed control to apply the above conclusion.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.2
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• pp.113-119
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• 2006

This paper studies the torque characteristics of CDTP controlled BLDCM with various back-EMF waveforms. We propose a CDTP method to suppress torque pulsation due to commutation time and point. It is adopted to control the BLDCM with real back-EMF waveforms through the Hague's method for minimizing torque ripple. Real back-EMF waveforms are produced with a magnetic fringing factor and crest width of back-EMF. The performance and characteristics of the proposed control method are analyzed by simulation and verified through experimental results.