Thermal Analysis of a Novel Linear Oscillating Machine Based on Direct Oil-Cooling Windings

High-frequency electromagnetic linear machine is one major component for linear eletro-hydraulic actuator that in turn is extrimely important for the flight control of more-electrical or all-electrical aircrafts. The employment of high-frequency linear machine helps to achieve high reliability and dynamic performance of the actuators. However, the capability of heat dissipation of the linear machine unavoidably constrains the input current, which in turn depresses its output performance. Therefore, this paper proposes a novel electromagnetic linear machine based on the self-powered direct oil-cooling windings. Specifically, the windings are immersed into the oil directly, which helps to decrease the temperature of the linear machine significantly and thus increase its output performance. In addition, the oil is pushed by the motion of the mover itself. No additional pump is required any more. Thus, the system can be simplified greatly. The design concept of high-frequency electromagnetic linear machine along with its operating principle is presented. A high-precision three-dimensional (3D) piecewise modeling method is proposed to simultaneously consider axial, radial and circumferential equivalent thermal circuits. Numerical simulation is conduced to validated the analytical model. A research prototype of the linear oscillating machine based on direct oil-cooling windings is developed and empolyed for experimental study, and the experimental result verifies the mathematical model of the thermal field well.