ABSTRACT:
This
paper presents a simple dc-link voltage modulation scheme to minimize the
commutation torque ripple in a Permanent Magnet Brushless DC Motor (PMBLDCM).
Maintaining a constant current in the non-commutating (NC) phase helps to
minimize the torque ripple, which can be achieved by boosting the motor input
voltage whenever two phase currents are undergoing commutation. At low speeds,
since the required ac voltage at commutation is also less than nominal, the
standard PWM operation of inverter with the nominal dc-link voltage suffices.
However, at higher speeds, a momentary (only during the commutation interval)
boost in the dc-link voltage (above the nominal level) is needed to ensure
boost in motor voltage, hence a steady current in the NC phase. In the proposed
scheme, the dc voltage boost at higher speeds is obtained by connecting two
capacitors in series which are normally connected in parallel across the
dc-link. The proposed scheme is verified for a 1hp PMBLDCM drive through
simulations and experiments in the laboratory. Results exhibit a notable
improvement in reducing the torque ripple.
KEYWORDS:
1.
Dc-link
voltage modulation
2.
Permanent
magnet brushless dc motor
3.
Commutation
torque ripple
A
simple capacitor switching based dc-link voltage modulation scheme to minimize
the commutation torque ripple in a PMBLDCM is presented in this paper.
Maintaining a steady value of the NC phase current by altering the dc-link
voltage can effectively minimize the torque ripple. PWM control of inverter at
low speed range and PWM control along with dc-link voltage modulation at high
speed range (proposed scheme) ensure a low torque ripple. A simple additional
circuitry is employed to momentarily boost the dc voltage to the inverter in
the high speed range. The DVM scheme offers a significant diminution in torque
ripple and a smooth and noise free operation of the PMBLDC machine.
REFERENCES:
[1] R. Krishnan, “Electric Motor Drives Modeling, Analysis and Control”, PHI Learning Private Limited, 2001.
[2] P. Pillay and R. Krishnan, “Modeling, simulation, and analysis of permanent-magnet motor drives, Part II: The permanent magnet synchronous drive,” IEEE Trans. Ind. Appl., vol. IA-25, no. 2, pp.265–273, Mar./Apr. 1989.
[3] R. Carlson, L.-M. Milchel, and J. C. Fagundes, “Analysis of torque ripple due to phase commutation in brushless dc machines,” IEEE Trans. Ind.Appl., vol. 28, no. 3, pp. 632–638, May/Jun. 1992.
[4] H. Lu, L. Zhang, and W. Qu, “A new torque control method for torque ripple minimization of BLDC motors with un-ideal back EMF,” IEEETrans. Power Electron., vol. 23, no. 2, pp. 950–958, Mar. 2008.
[5] J. Shi and T. C. Li, “New method to eliminate commutation torque ripple of brushless DC motor with minimum commutation time,” IEEE Trans.Ind. Electron., vol. 60, no. 6, pp. 2139–2146, Jun. 2013
