A wide range speed control method of compact high speed BLDCM using PLL approach

High speed compact BLDCM (Brushless DC Motor) is much used for a robot and medical application because of the high torque and high speed characteristics. This paper presents a simple PLL based speed control scheme for a high speed compact BLDCM. Without any complex calculation of actual speed and design of speed controller, a simple phase difference between reference and actual hall sensor signal is used for calculation current reference which is proportional to output torque of BLDCM. And the current reference acts for keeping the phase delay of two signals. So, the actual speed can keep the reference speed. Meanwhile, additional DC-link voltage controller, which adjusts link voltage of VSI inverter according to reference speed, can reduce current ripple in a wide speed range. The proposed control scheme is very simple and does not use any complex calculation. The proposed control scheme is verified by the experimental results of 40,000 rpm compact BLDCM.