Realization and Development of Radial-Flux Permanent Magnet Micromotor Utilizing MEMS 3D Solenoid Coils With Iron Core

Electromagnetic (EM) motors fabricated using a micro-electromechanical system (MEMS) have a broad application prospect as miniature actuators owing to their high power density. However, size and structural limitations, exist because the testing technology for micro motors is still immature, and the existing test data only focus on a few indicators, such as motor speed. In this study, the radial-flux permanent magnet (PM) micromotor with three-dimensional (3D) iron-core MEMS silicon-embedded coils of high aspect ratio (coil height/line width = 14) is tested systematically, including static performance, electrical parameters, temperature tolerance, and output parameters. The micromotor is in the form of a hexagonal prism with a thickness of 1.6 mm. The total weight of the micromotor is 3.552 g. The average resistance of the coils is $0.39~\Omega $ , with an average inductance of $1.060~\mu \text{H}$ . The tested results confirm that the back electromotive force (EMF) waveform is sinusoidal, with a back EMF coefficient of $2.89\times 10^{\text {-{4}}}\text{V}\cdot \text{s}$ /rad. With the internal heating power of 3.29 W, surface temperature of the micromotor is 78°C in the state of natural convection. The micromotor can be maintained at 582 rpm under 0.5 A input current and no-load condition. The complete test scheme proposed in this work is in favor of the test for millimeter-scale micromotors under development.