Modeling, analysis and optimization of magnetic gearbox using FEM finite element method

Master thesis in the field of electricity-power orientation

Abstract

Gearboxes are essential and inseparable components of power transmission systems. These machines convert torque into speed and sometimes speed into torque. The use of mechanical gearboxes in these systems has been common since a long time until now as an interface between the power generation sector and the power consumption sector. With the expansion of the use of these gearboxes, the problems and disadvantages of these machines have appeared and prompted designers to look for a suitable alternative to the mechanical gearbox. Magnetic gearboxes do not have many of the problems that plagued mechanical gearboxes due to the lack of physical contact between the internal and external rotors. Problems such as the need for lubrication and greasing of wheels, noise, the need for wheel repairs and so on.

In this thesis, we have examined magnetic gearboxes and then by choosing a sample of these gearboxes, we have sought to make changes in the direction of optimization and commercialization of this machine. The changes that have been made in this thesis on the gearbox include investigating the effect of changing the number of pairs of poles and also investigating the effect of the type of magnet used on the torque behavior of the machine. It has been well observed that the increase in pole pairs has increased the torque output from the system.

Key words: magnetic gearbox, increase in pole pairs, volume torque density and two-dimensional finite element method

Introduction

Gearboxes are one of the members of the power transmission system, and the task of the gearbox in these systems is to convert speed and torque. The gearbox has the task of changing the torque (power) and the engine speed and making it as desired by the consumer. Initially, mechanical gearboxes were made to perform this task.

Mechanical gearboxes have wide applications in industrial machines and power transmission. Although these gearboxes have many and very important features and advantages and have an undeniable role in the industry, they also have inherent and undeniable disadvantages that have made it inevitable to look for a suitable replacement for these gearboxes. Problems and disadvantages such as friction caused by the contact action mechanism, losses related to energy transfer such as heat, multiple lubrications and revolutions, and noise and auditory noises caused by the physical contact of the input and output shafts. These disadvantages increase the maintenance cost of these gearboxes and reduce the useful life of these gearboxes. Magnetic gearboxes can be a suitable solution for this problem and a suitable alternative to mechanical gearboxes[1].

Magnetic gearboxes are a new technology that has emerged quickly. The torque transmission mechanism without physical contact is the most important feature and advantage of these gearboxes. In other words, this characteristic and inherent feature separates the mechanical contact of the input and output shaft from each other, and this in turn eliminates the subsequent problems such as the problem of lubrication and cooling. The absence of physical contact also results in a significant reduction in hearing noise, increased reliability and protection against overload at maximum efficiency[2]. Extensive studies have been conducted in relation to the expansion, improvement of performance and efficiency of magnetic gearboxes, and many different models and designs have been presented in line with this goal. But all these designs have something in common. In other words, all of them have a common component, as you can see in Figure (1-1), the gearboxes consist of 3 main components: external rotor, internal rotor and fixed pole parts, the internal and external rotors are related to the high-speed shaft and the low-speed shaft, respectively. It creates a magnetic field in this layer.. According to the lens law, this field opposes the field that creates it and a field is created in the opposite direction. The poles installed in the outer rotor are coupled with the poles formed in the middle layer and rotate, which is in the opposite direction to the rotation of the inner rotor. Due to the difference in the number of internal and external poles, the rotation speed of the external rotor is lower than the internal rotor

The importance of examining magnetic gearboxes

From the past and with the invention of the steam engine, power transmission has always been one of the most important challenges facing designers and engineers. With the invention of gears and then mechanical gearboxes and the use of this new machine in the industry, the problems of using these devices have also appeared at the same time. The problems caused by the physical contact of the gears in these gearboxes.

With the advent of magnetic gearboxes and the lack of physical contact between the rotors, the biggest problem of mechanical gearboxes has been solved. These gearboxes were initially used for small purposes [1] and gradually with the advancement of technologies and the presence of chemical industries to produce better magnets, these gearboxes also entered heavy industries. In recent years, extensive studies have been conducted in the field of magnetic gearbox to increase output torque, increase efficiency and reduce torque fluctuations. A series of these works has been to prepare this new car to replace with mechanical gearboxes.

Another field of research on magnetic gearbox is trying to optimize this car. As mentioned earlier, the main components of this machine are magnetic poles made of permanent magnets. Nowadays, with the increase in the price of these permanent magnets and the exclusivity of the production of these materials for a few countries, the optimal use of these materials is necessary and inevitable.

So the necessity of research on magnetic gearboxes can be summarized in the following cases:

Increasing production torque

Increasing efficiency

Reliable and reliable torque production

Optimization

Reduction of the finished price and commercialization of the product

Applications of magnetic gearbox

Chemical industries [1]

Wind power plants[4]

Medical applications[6]

Domestic, medical and humanoid robots[6],[12]

Use in military industry[7]

Use in Pumps and pumps

Usage in cars[8]

Aviation industry[9]

Ship propulsion

Aerospace industry[11]

Abstract

Gears are inseparable and necessary parts of power transmission systems. These machines change torque into speed and sometimes they change speed into torque. Using mechanical gears in these systems has been common as a means of transforming the power from the generating motive force to the consuming section from old time up to now. By the expansion of gears usage their problems and shortcomings have arisen and made designers search for suitable replacement for these mechanical gears.

Magnetic gears, due to not having physical contact with internal and external rotors, do not have many of the problems that mechanical gears face such as periodic lubrication, greasing, noise, fixing and....   

In this thesis, we analyze magnetic gears, and then, by selecting one of them as a sample, we are to make changes for optimizing and commercializing this machine.