Torque Analysis for Rotational Devices with Nonmagnetic Rotor Driven by Magnetic Fluid Filled in Air Gap

Hong-Soon Choi,Gui-Hwan Kim

doi:10.3390/en14154669

Abstract

In magnetomechanical applications, it is necessary to calculate the magnetic force or torque of specific objects. If the magnetic fluid is involved, the force and torque also include the effect of pressure caused by the fluid. The standard method is to solve the Navier–Stokes equation. However, obtaining magnetic body force density is still under controversy. To resolve this problem, this paper shows that the calculation of the torque of these applications should not only use the magnetic force calculation method, but also consider the mechanical pressure using an indirect approach, such as the virtual work principle. To illustrate this, we use an experimental motor made of a nonmagnetic rotor immersed in a magnetic fluid. Then, we show that the virtual work principle in appropriate approach can calculate the output torque of the nonmagnetic rotor due to pressure of the magnetic fluid. Numerical analysis and experimental results show the validity of this approach. In addition, we also explain how the magnetic fluid transmits its magnetic force to the stator and rotor, respectively.

Highlights

IntroductionThere have been steady attempts to implement certain functions or improve performance using magnetic fluids in electric devices
Is same torque of the experimental is increased by is four times. This is the sameThis as the solid torque of of the themotor experimental motor is increased by four four times
The Navier–Stokes equation directly raises used as a forcing term, solving the Navier–Stokes equation directly raises a problem of reliability because the most important forcing term, the magnetic force density, is still under reliability because the most important term, the force density, still un- of the torque controversy

Summary

Introduction

There have been steady attempts to implement certain functions or improve performance using magnetic fluids in electric devices. Magnetic fluid has various mechanical, magnetic, and other properties and can be used in various devices and applications [1,2,3,4,5]. There are two main application categories: one is that it can move similar to a liquid by receiving magnetic force from a magnetic field. This is the basic principle of numerous magnetic fluid application microdevices, such as drug transport [6,7], micropumps [8], sensors [9], and actuators [10]. Several researchers are using this phenomenon to improve the efficiency and torque of various rotating machines, for example, induction machines [11,12], a linear motor [13], and an interior permanent magnet synchronous motor [14]

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Results

Conclusion