Determination of operating conditions of submersible induction motors

Adjustable-speed operations of induction motors are required to maintain their maximum efficiency levels. This can be achieved by constant slip operation of induction motors. In applications like submersible motor pumps, variable speed operation is also needed to obtain maximum efficiency at all loads. To maintain a constant slip operation of induction motors, it is necessary to monitor the motor´s speed from its shaft. Speed monitored by these sensors is fed back to maintain constant slip operation in scalar control schemes. However, such speed sensing and transmission of speed information to change the motor´s speed may become prohibitive in certain applications. A new method to determine a submersible induction motor´s speed from its terminal voltage and current is presented