High Efficiency Operation of Brushless DC Motor Drive using Optimized Harmonic Minimization based Switching Technique

 Abstract

This paper presents a new switching technique to minimize losses in a trapezoidal brushless DC motor (BLDCM) drive. Based on the analysis, a pulse width modulation (PWM) strategy with selective harmonics elimination (SHE) is projected for motor phase current for dynamic loss minimization of BLDC motor drive system. The proposed control technique uses SHEPWM to optimize pulse width modulation to minimize different losses at different loads and motor speeds based on a predefined look-up table. The efficacy of the control methodology is presented using proper simulation results in MATLAB/Simulink environment. The control methodology is also validated with an experimental prototype of 350W BLDCM drive system.

Index Terms

Brushless DC Motor (BLDCM), Loss Minimization.

Block Diagram:

Fig. 1. Circuit diagram of a three phase VSI fed BLDCM drive.

Expected Simulation Results:

Fig. 2. Simulated results using conventional control (a) Phase current,

                                                (b) Phase back emf and (c) FFT of phase current.

Fig. 3. Simulation result using proposed control (a) Phase current, and

                                                           (b) Phase current FFT waveform.

Fig. 4. Change of phase current with change in load (a) Simulated and (b)

Experimental waveform (5A/div).

Fig. 5. Speed and current change with constant rated load @ 350W BLDC Motor (a) Simulation and (b) experimental waveforms.

CONCLUSION

In the present work, SHE based PWM is used to eliminate dominant current harmonics, which enables to achieve better BLDCM drive efficiency with minimized losses. The motor losses have been minimized by eliminating lower order harmonics in phase current waveform. This has been achieved with an appropriate look-up table based on predicted transient current slope of the motor. The method can be applicable for both 120o and 180o inverter drive switching techniques. Suitability of the proposed loss minimization scheme is verified both through simulation and suitable experiments.

REFERENCES
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