Brushless permanent magnet motor for use in remote locations

Abstract

A brushless permanent magnet motor for use within a electric submergible pumping system is controlled without utilizing rotor position sensors, by sampling the voltage of the motor's windings. The operation of the motor is governed by control circuits that provide signals representative of the winding EMFs. The control circuits utilize an integrator, a offset corrector, and a crossover detector to simulate outputs received from Hall effect devices. Outputs from the control circuits are used to sequentially gate an array of commutation transistors to apply power to the different windings. These outputs are also used to develop a tachometer signal to regulate the speed of the motor, by controlling the supply voltage to the commutation transistors. Prior to starting the motor, the output bus voltage is permitted to rise from zero volts to a predetermined level. Then, the rotor rotates to a predetermined home position with regard to the stator. During this time, integrators are precharged to assist crossover detectors in establishing the initial timing relationship between the three motor phases. As the motor begins to rotate, the motor control is performed by detecting and processing winding EMFs, and operating the motor in a brushless D.C. mode.