Design of Cryogenic Induction Motor Submerged in Liquefied Natural Gas

This paper presents the design of cryogenic induction motor submerged in liquefied natural gas (LNG) for operating LNG spray pump. In cryogenic environment of -163 °C, the torque characteristics of induction motor differ greatly from the operating conditions at room temperature. So, in order to obtain the operating characteristics corresponded with design specifications of the induction motor in cryogenic environment, it is necessary to redesign motor dimensions from the result of conventional design by reflecting the changes of material properties under the very low temperature (VLT). This paper focused on the design of cryogenic induction motor considering the variation of resistivity for the stator windings and rotor bars. Also, the distribution of magnetic flux density and magnetic saturation effect on the steel core are analyzed by using 2-D finite-element method for ac sinusoidal time varying excitations under the VLT. The result of proposed method considered the magnetic and electric characteristics of matters in VLT successfully, so that the motor performances at the cryogenic temperature fit well with expected. The designed motor was fabricated and torque performance measured in VLT agreed well with design goals.