Efficiency Improvement for Submersible Motors by Optimizing the Ratio of Diameter to Shaft Length

Aiming to improve the efficiency of the water-filled submersible motor, the method of optimizing the ratio of diameter to shaft length and air-gap length of the motor is proposed to reduce the water friction loss of the water-filled submersible motor. By analyzing the composition of the mechanical loss and the research status of the water friction loss of the water-filled submersible motor, the optimization methods of the water-filled submersible motor efficiency are determined. For the accurate estimation of electromagnetic performance of the submersible motor, 2-D time-harmonic field solutions are employed, which cost less time and computational resources compared to the transient solution. By fitting the curves of water friction loss and electromagnetic losses with the optimized parameters, the influence of the ratio of diameter to shaft length and the length of the air-gap on the efficiency of the motor is analyzed. Finally, the parameters of the motor are determined, with the consideration of the influence of the radial to axial ratio and the air-gap length on the performance parameters of the motor and the requirements of actual working conditions. The results show that the two methods can effectively reduce the water friction loss of the water-filled submersible motor and improve the efficiency of the water-filled submersible motor in the motor design stage.