A submersible motor with an advanced delta modulated inverter driver

The delta modulator can provide constant voltage over frequency (constant v/f) control up to the motor base speed and smooth transition to constant voltage mode of operation beyond the base speed. The proposed delta modulator optimizes the slope of the feedback signal, window width and magnitude of the DM reference signal. It has been found that a proper selection of these parameters play a vital role on the design of a 3-phase IGBT based VSI for superior performance of submersible induction motor. Since tacho feedback or other traditional speed sensing means is not permissible in a sealed motor or the pump, a novel method is used to monitor the motor speed from the terminal quantities like voltage, current and motor input power factor. A semi closed loop operation of the motor is proposed