Sources of torque ripple and their influence in BLDC motor drives

Abstract

Abstract In automotive applications brushed DC motor is often used because of its simplicity and low price. It is very quiet motor, easy to control and serves as actuators with an overall short operating time. Brushless DC (BLDC) motors have less wear and probability of failure, higher efficiency, but need a more complex control algorithm than a DC motor drive. So brushless DC motor is most suitable for applications demanding long-term continuous duty like fuel pumps. Brushed DC motor is often used also in seat ventilation and in some HVAC (heating, ventilation, and air conditioning) compressors and blowers where low noise operation is required. There is an effort to replace this brushed DC motor with low-cost BLDC motor. But problem of these low-cost BLDC motors is in produced torque ripple, vibrations and acoustic noise. Therefore, sources of torque ripple and their suppression has to be identified. This article will be focused on identification of main sources of torque ripple caused by construction and control of BLDC motor. Sources such as cogging torque, waveform of Back-EMF in combination with waveform of phase currents (type of control technique), dead-time and commutation of currents will be investigated. Impact of these sources will be identified on real BLDC motor and also torque ripple, vibrations and acoustic noise will be evaluated in this article.