Cryogenic Characterization of Copper-Wound Linear Tubular Actuators

Electrical machine power density can be increased by liquid nitrogen (LN) cooling, since these machines operate at low resistivity and have a high heat transfer coefficient. This paper describes the experiments carried out on a short stroke tubular linear permanent magnet machine with copper windings and LN cooling. A cryogenic test rig for linear actuators was designed and built, and tests were carried out aimed at highlighting inherent current limiting capability, electric parameter variation in the fall from room to cryogenic temperatures, and actuator high thrust density. Shear stress reaches 17.8
$\hbox{kN/m}^{2}$
, and thrust-to-copper-loss ratio is 4
$\hbox{N W}^{-1/2}$
, which are significantly better compared to conventional actuators.