Magnetic Circuit Design and Experiment of Novel Lorentz Magnetic Bearing with Double Air Gap

Abstract

A uniform magnetic density distribution in the air gap is key for the Lorentz magnetic bearing to achieve high precision control and large torque output. To overcome the small magnetic field strength in an explicit magnetic bearing and a high magnetic density fluctuation rate in an implicit Lorentz magnetic bearing, a second air gap design method is proposed based on the maximum magnetic density distribution in the winding area. A novel Lorentz bearing with a double second air gap is designed. The maximum magnetic field strength in the winding area is calculated by the finite element method, and the structure of the double second air gap is designed. To reduce the calculation error of the magnetic field strength, the division of the reluctance by the magnetic induction line is proposed. The reluctance calculation formula is given. Based on Ohm’s law, the calculation of the magnetic field strength is obtained. Finally, a prototype of the novel Lorentz magnetic bearing is made. The magnetic field strength in the winding area and the magnetic density fluctuation rate are measured with a magnetic density measurement instrument. The maximum magnetic flux density in the winding area is 0.631 T, and the magnetic field strength is 0.58%. Less difference is found between the measurement result and the finite element result.