Rotating Cryocooler for Superconducting Motor

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A single‐stage coaxial pulse tube refrigerator has been designed for HTS (High Temperature Superconductor) motor application. This paper discusses a practical realization of an advanced cooling method for superconducting rotor, on‐board cryocooler. When a cryocooler is considered to be mounted on the superconducting rotor, the following two factors must be satisfied for practical application. First, the on‐board cryocooler should not disturb the high‐speed revolution of the rotor. Second, at the same time, the high‐speed revolution of the rotor should not deteriorate the cooling performance of the cryocooler. These mutual technical demands restrict the type of cryocooler suitable for high‐speed rotating environment. We select a Stirling‐type coaxial pulse tube cryocooler and incorporate it on the 1800‐rpm superconducting motor mock‐up. The pulse tube cryocooler is designed with an adiabatic model and a various loss mechanism analysis. The no‐load temperature is approximately 100 K with less than 150 W electric input power. The axisymmetric configuration of the fabricated cryocooler does not produce any undesirable effect at high‐speed rotation. Even if the thermal performance of the rotating pulse tube cryocooler is not satisfactory, the feasibility of simple on‐board cooling method for superconducting rotor is confirmed in this paper.