Design and Analysis of High-Speed Induction Machines for Submerged Cryogenic Pumps

This paper discusses the electromagnetic design and loss analysis of a 15 kW, 13500 rpm induction machine for a single-stage submerged cryogenic pump. The study starts from an existing machine driving a three-stage cryogenic pump, rated 7.5 kW at 7300 rpm. The new motor design is approached by increasing the rotating speed of the reference machine at fixed outer diameter, aiming at an optimum between efficiency and power factor. Experimental investigations are carried out on the reference machine to analyze its thermal behavior. The results allow to obtain initial values for the electrical loadability of cryogenic induction machines. The electromagnetic design of the high-speed motor is successfully carried out with the help of detailed numerical simulations, particularly devoted to a precise analysis of the losses active in the machine. Special care is given to the iron losses, estimated with two different approaches.