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

• Journal of Power Electronics
• /
• v.18 no.4
• /
• pp.1086-1098
• /
• 2018

This study presents a new sensorless commutation method for brushless direct current motors to replace Hall sensor signals with virtual Hall signals. The importance of the proposed method lies in the simultaneous elimination of the phase shifter and the low-pass filters, which makes the method simple and cost-effective. The method removes high ripple switching noises from motor terminals, thereby decreasing motor losses. The proposed method utilizes unfiltered line voltages with notches caused by current commutation. Hence, specific sign signals are defined to compensate for the effects of commutation noise. The proposed method is free from phase delay that originates from low-pass filters. The method directly produces virtual Hall signals, and thus, it can be interfaced with low-cost commercial commutation integrated circuits based on Hall sensors. Simulation and experimental results show the effectiveness and validity of the proposed method.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.48 no.9
• /
• pp.490-497
• /
• 1999

This paper presents a novel current control method to reduce the current ripple due to commutation in brushless DC motor fed with unipolar PWM voltage source inverter. The proposed current control method can reduce the current ripple due to commutation in high speed range where the DC link voltage of the inverter is less than four times of the phase back-emf. The effectiveness of the proposed current control method is verified with digital simulations and experiments on the 250W brushless DC motor drive systems.

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

• The Transactions of the Korean Institute of Power Electronics
• /
• v.8 no.1
• /
• pp.56-63
• /
• 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 Industrial Technology
• /
• v.24 no.A
• /
• pp.109-117
• /
• 2004

This paper presents a current control strategy to reduce torque ripple of Brushless DC Motor in commutation period with PWM pattern. The torque ripple is mainly caused by the inequality in the rate of change between rising current and decaying one during commutation. And also it is influenced by the shape of real back EMF. Therefore, in the proposed control strategy, considering real back EMF a compensation voltage is generated to equalize the rate of change in these commutating currents. And then, by providing the compensation voltage in commutation period with PWM pattern, the torque ripple can be reduced. The simulation and experimental results verify that the proposed method can reduce the torque and the current ripples significantly.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.11 no.5
• /
• pp.431-439
• /
• 2006

This paper proposes a new commutation circuit for a PWM Cuk AC-AC converter. The proposed commutation circuit utilizes a modified Undeland snubber as a commutation aid. The snubber circuit has some good features such as reduction of voltage/current stress of the main switches and improved efficiency. The experiment results show the adaptability and feasibility of the proposed commutation circuit.

• Proceedings of the KIEE Conference
• /
• 1988.07a
• /
• pp.117-120
• /
• 1988

A new current source inverter (CSl) with dc-side commutation and load-side energy recovery circuit is proposed with analysis and explanation of the circuit operation. Proposed inverter overcomes the most drawbacks of the conventional CSI's - high device voltage stress, low operating frequency range, large commutation capacitance, etc. - by employing simultaneous recovery and commutation concept. The new CSI employs only one commutation capacitor and it can be built with considerably low cost. The commutation energies are temporarily stored into a large dc capacitor and recovered to the load side, thus the device voltage stress is low and the efficiency is high in the proposed inverter. Computer simulation results are given at the steady state, and a guideline determining the commutation circuit is given.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.49 no.1
• /
• pp.1-8
• /
• 2000

Switched reluctance motor(SRM) has simple magnetic structure, and requires simple power electronic driving circuit. It is very useful for wide range adjustable speed drive system. But, SRM drive generates large vibration and acoustic noise because it is commutated individually by step pulse m.m.f of each phase pole. In the vibration and acoustic noise characteristics. The considerable vibration and noise is induced by radial deforming of stator, so the frequency of dominant vibration and noise is coincident with the frequency of natural mode frequency of mechanical structure. This radial vibration force is generated in the phase commutation region. This paper suggests the new electromagnetic structure of SRM with auxiliary commutation winding which is excited by direct current. This phase and commutation winding are coupled magnetically between one phase winding and the other. Therefore, the switch-off phase current is absorbed by the another phase winding. By this interaction of phase and commutation winding in commutation mechanism, vibration and noise is reduced. And this reduction effect is examined by the test of prototype machine. As a result, SRM with DC exciting commutation winding is very useful to reduce vibration and acoustic noise.

• 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.