Novel Methodology for Sensorless Control of Three Phase Variable Inductance BLDC Motor Driven Thruster for under Water Applications

This paper presents a novel methodology for sensorless control of three phase BLDC motor driven thruster utilizing variable inductance nature. The methodology proposes utilization of peaks and valleys of the phase inductance to generate commutation instants/firing sequence for sensorless control. It is shown through simulation studies of a BLDC motor incorporating position dependent inductances that the firing instants corresponds to peak or valley points in the line inductance. The same is also validated through finite element analysis and experimental studies of the motor. A sensorless control scheme is proposed based on these observations.