Novel torque boost technique for brushless DC motor drives without current sensor

The paper contributes to the presentation of a compensation technique for brushless DC motor drives. The presented technique overcomes the time delay issue caused by the time constant of stator windings of brushless DC motor. The time delay issue results in phase shift between back-EMF and phase current; and thereby reducing the output torque and efficiency. The basic idea for the presented technique is to shift the commutation instant forward such that the back-EMF and the current can be in phase even under the influence of time delay caused by stator windings. It will be shown that no current sensor is required for the presented torque compensation technique. Comparison results derived from experimental system with and without torque compensation technique are presented to support our claims. It will be shown that the presented technique increases efficiency in the whole output range.