High temperature operation of multi-watt, axial-flux, permanent-magnet microgenerators

This paper presents the characterization and modeling of a permanent-magnet (PM) microgenerator operating at high temperatures. Due to the thermal dependence of the relevant properties of the conductor and magnetic materials, degradation of the output electrical power with increased temperature is expected. Each material of the PM microgenerator is magnetically or electrically characterized up to 375 °C. For a rotor designed for high temperature operation using SmCo magnets, 2.7 W of DC power has been obtained at 100 °C and 210,000 rpm, which is a 35% drop as compared to the output power at room temperature. This result is in good agreement with theory. Calculations showed that this PM generator is capable of 2.4 W of DC output power at an operating temperature of 300 °C if the rotational speed is increased up to the 300,000 rpm, as achieved with previous room temperature devices. This work demonstrates that MEMS-based permanent-magnet microgenerators are good candidates as a component of a heat-engine-driven electrical power generation system.