Development of mountable electromagnetic induction type MEMS generator

This paper proposes a three-phase type MEMS air turbine generator. The developed generator is combined with a silicon air turbine and a ceramic magnetic circuit. The magnetic circuit for an electromagnetic induction type generator is fabricated by the multilayer ceramic technology. The fabricated multilayer circuit realizes a three-dimensional coil structure inside the monolithic ceramic structure. Moreover, the circuit shows low internal DC resistance because Ni-Cu-Zn ferrite and silver conductor are used for the magnetic material and the coil pattern. The miniature air turbine is fabricated by the MEMS process. To achieve the high rotational speed, the miniature ball-bearing is used, and the rim-shape rotor is used. In this generator, the distance between the magnet and the magnetic circuit is important factor. The magnet is held by the shaft through the ball-bearing and rim-type rotor, and it showed narrow distance to the magnetic circuit. Dimensions of the fabricated MEMS generator were 6.17 mm, 5.62 mm and 7.12 mm, length, width and height. The maximum rotational speed of the fabricated electromagnetic induction type MEMS air turbine generator was 228,484 rpm, when the flow rate was 2.9 l/min and the pressure was 0.3 MPa. The maximum three-phase output power was 3.01 mVA at load resistance of 3 ohm. The achieved value was 42 % of the theoretical power. The reason is alignment error of the coil pattern. To achieve more high output power, the alignment pattern will be introducing to suppress the assembled error.