A variable reluctance based rotational electromagnetic harvester for the high-speed smart bearing

In recent years, smart bearing technology is being developed for the purpose of prolonging the reliability and the service time of bearing by detecting the early faults and regulating the working condition. However, powering wireless monitoring devices integrated within the smart bearing is still an uphill task due to the limited power capacity and lifetime of traditional power cells. In this paper, a variable reluctance energy harvester (VREH) is proposed to scavenge the rotating energy from the bearing, which includes a toothed spacer and an m-shape electric steel with a coil and a permanent magnet on each leg. The key parameters of the proposed harvester are analyzed and discussed via the theoretical study and the finite element analysis. In comparison with the VREH without the middle magnet, the proposed harvester greatly improves the energy harvesting performance and reduces the magnetic flux leakage to the ferromagnetic environment. Simulation results show that for the air and ferromagnetic environments, the average output power improvement of the VREH with the middle magnet reaches 33.89% and 61.6%, respectively. A fabricated prototype is tested using the high-speed railway bearing testing machine. The influence of the impedance matching circuit and the coil connection on the VREH is investigated with the rotating speed varying from 600 r min⁻¹ to 1800 r min⁻¹. An energy management and storage circuit is designed and fabricated to test the energy conversion performance of the proposed harvester. Under the impedance matched condition, the optimal root mean square (RMS) output power is of 72.13–414.86 mW. It is shown that the proposed electromagnetic harvester is capable of collecting the rotational energy in the ferromagnetic environment and can be used for the high-speed smart bearing applications.