Permanent Magnet Couplings Research Articles

3D analysis of eddy current loss in the permanent magnet coupling.

This paper first presents a 3D analytical model for analyzing the radial air-gap magnetic field between the inner and outer magnetic rotors of the permanent magnet couplings by using the Amperian current model. Based on the air-gap field analysis, the eddy current loss in the isolation cover is predicted according to the Maxwell's equations. A 3D finite element analysis model is constructed to analyze the magnetic field spatial distributions and vector eddy currents, and then the simulation results obtained are analyzed and compared with the analytical method. Finally, the current losses of two types of practical magnet couplings are measured in the experiment to compare with the theoretical results. It is concluded that the 3D analytical method of eddy current loss in the magnet coupling is viable and could be used for the eddy current loss prediction of magnet couplings.

Wireless power transfer system for a human motion energy harvester

Human motion energy harvesting as an alternative to battery powering in body worn and implanted devices is challenging during prolonged periods of inactivity. Even a buffer energy storage system will run out of power eventually if there is no external acceleration to the harvester. This paper presents a method to actuate the rotor inside a previously presented rotational piezoelectric energy harvester wirelessly via a magnetic reluctance coupling to an external driving rotor with one or more permanent magnet stacks attached. This makes it possible to recharge a battery or super-capacitor even if a patient is not moving. The use of a permanent magnet coupling has potential advantages compared to traditional inductive or ultrasonic methods, e.g. in terms of tissue damage and transmission depth. Simulation results show the achievable coupling torque for different configurations of magnet geometries and relative positions between the driving magnet stack(s) and the harvester. It is shown that using a single magnet stack yields better results than using two diametrically opposite stacks. Measurements are performed with different magnets, driving frequencies and orientations of the harvester. The results are discussed and successful energy transfer was achieved regardless of the orientation of the device with respect to gravity, which is desirable for real world applications. Lateral misalignment between the harvester and the driving magnet can also be overcome. The largest distance of power transfer reached was 32mm with the largest magnets tested, and the optimal power output into a resistive load was over 100μW at a frequency of 25Hz. The functional volume of the harvester is 1.85cm3 – similar to the size of a wristwatch.

Characteristic Analysis of Adjustable Permanent Magnetic Coupler with Slotted Conductor Disk

Characteristic Analysis of Adjustable Permanent Magnetic Coupler with Slotted Conductor Disk

Operation and Improvement of Liquid Nitrogen Pumps with Radial High- Temperature Superconductor Bearings

This paper reviews the advantages of replacing the mechanical bearings of low-temperature pumps by radial high- temperature superconductor (HTS) bearings. Radial HTS bearings have the advantage of being non-abrasive, so that the working life is increased significantly. In this article, two types of liquid nitrogen pump with radial HTS bearings are proposed. To reduce heat leakage, one pump uses a permanent magnet (PM) coupling and the other uses a long hollow pipe coupling. Successful stable operation of these two pumps means that radial HTS bearings have the potential to be applied in liquid nitrogen pumps. Test results show that the flow rate is influenced mainly by rotational speed but not by the coupling component. Further designs of the two types of pump for practical applications are described, and their characteristics are analyzed: the pump with a PM coupling has lower heat leakage, whereas the pump with a long hollow pipe coupling can solve the force creep problem of the HTS bearing. The design of the pump with a long hollow pipe coupling is based on the pump that is already in practical use, and therefore has greater feasibility for practical applications. Finally, improvements of the liquid nitrogen pump by improving the structure of the pump and the performance of the radial HTS bearing are discussed.

3-D Analysis for the Torque of Permanent Magnet Coupler

This paper first presents a 3-D analysis model for calculating the torque transmitted between the permanent radial magnet couplers based on the Coulombian model. Then, a 3-D finite-element analysis model is constructed to analyze the spatial distributions of the magnetic field and end effect of the axial length of the magnet coupler. Besides, the parametric studies of the magnet coupler are taken using the two 3-D models, respectively, and the simulation results obtained are analyzed and compared. Finally, two kinds of real applied magnet couplers are tested to compare with the results with the 3-D analysis model. It is concluded that the 3-D analytical model of the torque of the radial magnet couplers is viable and could be used for the design of magnet couplers.

Characteristics Measurement of Electric Motors by Contactless Eddy-Current Magnetic Coupler

Torque-speed characteristics measurements are essential in the design and manufacture of electric motors. Dynamometers have been widely used in motor characteristics measurements, and the coupling between the motor under test and dynamometer is a critical issue for high-power electric motors. This paper develops a contactless measurement system, which consists of a permanent magnet (PM) coupler and requires no dynamometer. The torque of the PM coupler is transmitted by the eddy-current and controlled by the air gap inside the coupler. An equivalent circuit model of the magnetic coupler is derived theoretically and then verified experimentally under different operating conditions. The capacity of the proposed measurement system can also be determined in order to provide sufficient and accurate measurement information for the tested motors. A 1.5 kW dc motor with a maximum torque of 8.15 N-m was tested as an illustrated example. The experimental results are given to show the effectiveness of the proposed approach.

Experimental Research on Energy-Saving Application of Permanent Magnet Speed Regulation Technology

Permanent magnet speed regulation is an energy-saving technology that uses magnetism coupling to realize the torque transmission of non-mechanical connection and changes the gap of the permanent magnetic coupler to adjust the speed of the load. Experimental research on the air-cooled permanent magnet speed regulation according to the actual operation parameters of 500 kw oxidation fan has been conducted in this paper. Analyses of the problems about the rupture of the load ring at the end of the load on the permanent magnetic speed regulation, large motor vibration, noise and so on appeared during the process of the test have been made and improved measures are proposed.

Torque Analysis and Experimental Testing of Axial Flux Permanent Magnet Couplings Using Analytical Field Calculations Based on Two Polar Coordinate Systems

Axial flux permanent magnet couplings (AFPMCs) are widely used in industrial applications because of their attractive feature that the torque produced by them can be transmitted without any mechanical contact. This paper presents an analysis of the characteristics of AFPMCs with axially magnetized permanent magnets (PMs), based on an approach utilizing space harmonic methods. Analytical field computation is performed by applying a magnetic vector potential and a 2-D analytical model that employs two polar coordinate systems. We thus obtain solutions for the magnetic field distribution produced by PMs that are comparatively easier than using a single polar coordinate system. AFPMC torque is obtained from the analytical solution for magnetic flux density, caused by the PMs, and a Maxwell stress tensor. The analytical results are extensively validated using the 3-D finite element analysis and experimental results.

Comparative Study of Torque Analysis for Synchronous Permanent Magnet Coupling With Parallel and Halbach Magnetized Magnets Based on Analytical Field Calculations

This paper presents a comparative study of torque analysis for synchronous permanent magnet couplings (SPMCs) with parallel- and Halbach-magnetized magnets, using analytical field calculations. On the basis of the magnetic vector potential, we derived analytical solutions for the magnetic field produced by the interaction between the inner and outer PMs for the parallel- and Halbach-magnetized cases. Then, we calculated the magnetic torque using the derived solutions and Maxwell stress tensor. Our analytical results are verified using both 2-D and 3-D finite element analysis and experimental results. We found that SPMC with Halbach-magnetized magnets exhibit dominant pull-out torque than SPMC with parallel magnetized magnets.

Optimum Design and Comparison of Slip Permanent-Magnet Couplings With Wind Energy as Case Study Application

With eddy-current couplings proposed for and applied in several industrial applications, it is essential that these types of electrical machines be more thoroughly evaluated. In this paper, the feasibility of replacing the classical eddy-current coupling topology with a toothed slip permanent magnet coupling (PMC) is investigated. The case study application in this paper for the slip PMC is for a new type of wind generator concept known as a slip synchronous permanent magnet generator. Several different slip PMC technologies are evaluated, and a number of interesting novel concepts are introduced. These different topologies are optimized by means of finite element (FE) analysis for minimum active mass. The FE results are verified with practical measurements on several different prototypes.

Research on Overloading Protection of Permanent Magnetic Coupler in Coal Mine

In this paper, with simulations and experiments analysed by the software of Ansoft Maxwell, research on overloading protection of permanent magnetic coupler in coal mine is carried out and the conclusive curves of mechanical characteristics are plotted through experimental data. The conclusion can be gained from mechanical characteristic curves: when the output value of torque reaches the maximum torque of magnetic coupler, the output torque and speed will drop along with increases of the slip, and the input power value of motor is less than the power value at the time when the motor torque value is at the maximum. It explains that the magnetic coupler has the function for overloading protection.

Parametric Analysis and Experimental Testing of Radial Flux Type Synchronous Permanent Magnet Coupling Based on Analytical Torque Calculations

This paper presents the torque calculation and parametric analysis of synchronous permanent magnet couplings (SPMCs). Based on a magnetic vector potential, we obtained the analytical magnetic field solutions produced by permanent magnets (PMs). Then, the analytical solutions for a magnetic torque were obtained. All analytical results were extensively validated with the non-linear a two-dimensional (2D) finite element analysis (FEA). In particular, test results such as torque measurements are presented that confirm the analysis. Finally, using the derived analytical magnetic torque solutions, we carried out a parametric analysis to determine the influence of the design parameters on the SPMC's behavior.

THREE-DIMENSIONAL ANALYTICAL MODEL FOR AN AXIAL-FIELD MAGNETIC COUPLING

In this paper, we propose an analytical method for modeling a permanent magnets axial fleld magnetic coupling. The three-dimensional model takes into account the radial fringing efiects of the coupler. The analytical solution requires resolving the Laplace equation in low permeability subdomains. The magnetic fleld calculation allows the determination of global quantities like axial force and torque. 3D flnite element computations as well as measurements validate the proposed model.

Transmission Characteristics of Axial Asynchronous Permanent Magnet Couplings

In order to study the transmission characteristics of a new-type axial asynchronous permanent magnet coupling with 18 poles and 16 slots, the theoretical calculation method of the torque is obtained by theory of layered model firstly; then the distribution of 3D transient air gap field and the influence of different working parameters on torque characteristics are obtained; lastly, the 3D air gap field and torque in different working conditions are measured by the measure system of three-dimensional magnetic field and magnetic drive experimental platform, and the relationship curves between different working parameters and torque or efficiency are achieved. The results of simulation and experiment show that: the maximum magnetic flux density occurs at the magnetrotor, the magnetic flux density of the yoke iron attached to magnetic poles is also large; the axial flux density is the main component of air gap flux density; the axial flux density and the torque increase when the air gap thickness decreases;while the slip ratio and input speed increase respectively, the torque increases but the axial flux density decreases; the slip ratio increases slightly in a linear way firstly and then quickly with the increasing of the output torque, while the transmission efficiency firstly increases but then decreases slightly, particularly,at the 3% slip ratio the efficiency is up to the maximum; under the given 6% slip ratio the efficiency almost keeps about 94% when the input power increases, which verifies the law that the summation of slip and efficiency is constant 1; the efficiency keeps about 95% and the slip ratio is between 2% to 6% when the torque is between 26 and 48 N·m, by which excellent transmission characteristics and high efficiency could be proved in the heavy load working condition.

Design and Demonstration of a Test-Rig for Static Performance-Studies of Permanent Magnet Couplings

The design and construction of an easy-to-use test-rig for permanent magnet couplings is presented. Static torque of permanent magnet couplings as a function of angular displacement is measured of permanent magnet couplings through an semi-automated test system. The test-rig is capable of measuring torque up to 240 Nm (in increments of 0.1 Nm) at a angular step of 0.0011 degrees (mechanical). Axial, radial, and angular misalignment can be imposed on the coupling in order to study abnormal and faulty operating conditions. This can also be used to assess installation tolerances. Measured data is stored in a USB thumb-drive, and no additional software or hardware is needed to operate the test-rig. Tests of the aligned static torque performance of two different cylindrical couplings are presented along with radial and axial misalignment-tests of one. The results demonstrates the diversity and usefulness of the the designed test-rig. Furthermore, the coupling-performance shows a clear influence of end-effects for axially short couplings, and are found to be very robust to small misalignment.

The Torque Research for Permanent Magnet Coupling Based on Ansoft Maxwell Transient Analysis

We simulated the output torque relation and transient magnetic field for permanent magnet coupling in different states using Ansoft Maxwell 3D software, we can conclude that the design device can obtain large and smooth torque output and be suitable for mine working environment. We tested and verified the conclusion with experiment at the same time,and analysed deviation ,this provided the basis for conformation optimization and function analysis for permanent magnet coupling.

Design and Analysis of Axial Permanent Magnet Couplings Based on 3D FEM

Magnetic couplings are of considerable interest for many industrial applications because they can transmit torque from a primary driver to a follower, without mechanical contact. In particular, as they allow torque to be transmitted across a separation wall, axial permanent magnetic couplings (APMCs) are well suited for use in isolated systems such as vacuums or high-pressure vessels. This paper deals with the design and analysis of APMCs based on 3D finite element (FE) analysis. Finally, confirming that 3D FE results for the torque of the designed APMCs are validated extensively with the measured results, the validity of the design of the APMCs that satisfies the required specifications is confirmed. With the many advantages mentioned above, a permanent magnet coupling can be applied to a variety of industries.

Torque Analysis and Measurements of Cylindrical Air-Gap Synchronous Permanent Magnet Couplings Based on Analytical Magnetic Field Calculations

This paper presents the torque analysis and measurements of cylindrical air-gap synchronous permanent magnet couplings based on analytical magnetic field calculations. Employing a magnetic vector potential and a 2-D analytical model with two polar coordinate systems, we obtain the magnetic fields produced by permanent magnets. Then, the analytical torque solutions are derived using these magnetic field solutions and a Maxwell stress tensor method. The analytical results are validated by nonlinear 2-D and 3-D finite element results. Finally, torque measurements are presented to show the effectiveness of the analysis.

Numerical calculation of the outer thickness of double-solid rotor asynchronous permanent magnetic coupling by finite element method

Double-solid rotor magnetic coupling is a new type of asynchronous permanent magnetic coupling developed on the Electromagnetic Induction Theory. The rare permanent magnets are laid on the outer rotor only. The new-type magnetic coupling can effectively solve the problem of the former magnetic pump's failure to carry high-temperature medium, and thus possesses higher economic value and brighter prospects. The working performance of magnetic coupling depends on the thickness of the outer layer of the inner rotor. The double-solid rotor asynchronous magnetic coupling is analysed using the software ANSYS, and the veracity is demonstrated by experiment.

Design and fabrication of magnetic couplings in vacuum robots

PurposeThe purpose of this paper is to discuss the design and fabrication of magnetic couplings to use for vacuum robots. The permanent magnetic coupling (PMC) is appropriate for torque transmission in ultrahigh vacuum and highly clean environments. However, conventional structures of PMC are always unsuitable to use for vacuum robots.Design/methodology/approachTwo types of design scheme for radial magnetic couplings are introduced and compared. The major characteristic of the novel design scheme is that the inner part uses a nonmagnetic mantle to enclose the magnets and yoke, and the outer part uses two end closures to position magnets. The locating groove on the end closure may be manufactured as T‐shape or dovetail shape.FindingsThe 3D finite element analysis simulation results and experimental studies have demonstrated that the proposed Design B had a lower contamination rate and a higher transmission efficiency than the Design A.Research limitations/implicationsThe limitation of the research to date is that issues of control, path‐planning, and communication have not yet been addressed.Practical implicationsThe proposed PMC is successfully applied in vacuum robots which uses combined direct drive techniques and magnetic transmit techniques.Originality/valueThese results suggest that the proposed PMC is suitable for using in vacuum robots.