Design and performance of a new technique for sensorless control of a downhole brushless PM motor

A new technique for sensorless control of a downhole brushless PM motor connected through a long cable has been described. The cable was assumed to be represented by an RL equivalent circuit. The position estimator structure is simple because its avoids the problems of integration and differentiation of voltage and current signals. The practical implementation of the technique using a DSP system revealed that the noise on the estimated position makes it is necessary to retune the drive, to reduce the response time of its speed control system. Without any special starting procedure, which requires control of the switching of the inverter devices, the motor starting and reversing performance is not satisfactory. Work is in progress to improve the starting and reversing performance of the drive.