Radial Passive Magnetic Bearing Research Articles

Comparative study of passive magnetic bearing using four ring magnets: a critical review

Researchers on reducing energy losses caused by friction in small-scale wind turbines. This is crucial because a significant amount of energy is wasted due to friction in the main roller bearing. In order to overcome this, the concept of levitation has gained popularity. Levitation is achieved by employing the repelling forces between two opposing poles of a permanent magnet (PM), significantly reducing friction between the turbine stator and rotor. As a result, the overall energy production of the turbine increases. The use of passive permanent magnet bearings has several disadvantages, such as limited load-bearing capacity and rigidity. To address these limitations, we conducted numerical studies on four different configurations in order to enhance load-bearing capacity and stiffness. The results showed that the radial configuration outperformed the axial-type configuration in terms of stiffness and load-bearing capabilities in all four arrangements. Furthermore, it was revealed that radial passive magnetic bearings with adequate air gaps are not only more efficient but also less expensive than employing iron cores at the rear and between ring magnets for small-scale wind turbines.

Comparison of Acoustic Noise and Vibration in Ball-Bearing-Supported Motors and One-Axis Actively Positioned Single-Drive Bearingless Motor With Two Radial Permanent-Magnet Passive Magnetic Bearings

This study experimentally investigates the acoustic noise, vibration, and power consumption in a one-degree-of-freedom actively positioned single-drive bearingless motor, which has radial passive magnetic bearings (RPMBs) and compared to an identical stator part and rotor shaft with radial mechanical ball bearings. For the experiment, three test motors were set up: (a) a bearingless motor with two RPMB, (b) a motor with two ball bearings without an axial preload, and (c) a motor with two ball bearings with an axial preload. Motor (a) under test had one-axis active positioning and the radial movements were supported by RPMB made of cylindrical permanent magnets. Conversely, in motors (b) and (c), the radial and axial movements were supported by ball bearings, and there was no production of active axial force. The experimental results confirmed that the levels of acoustic noise, stator vibration, and input power consumption were significantly lower in motor (a) than those in motors (b) and (c). In the analysis section, dynamic models of the bearingless motor with RPMB and motor with ball bearings were designed and simulated using MATLAB <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\backslash$</tex-math></inline-formula> Simulink. The low radial stiffness in RPMB was found to contribute to acoustic noise and vibration reductions. Thus, this article presents an example of a one-degree-of-freedom actively positioned bearingless motor with RPMB that realizes reductions of acoustic noise, stator vibration, and input power consumption.

Passive Radial Bearing With Active Damper for Downhole Natural Gas Compressor

Design of radial passive magnetic bearings with active dampers (radial PMB-AD) and their application in a down-hole natural gas compressor (DHGC) are discussed. These compact and reliable bearings allowed noncontact suspension of a high-speed DHGC rotor spinning at 50 kr/min in a highly adverse environment more than 3 km (10 000 ft) below the ground with temperatures reaching 100 °C. The design was further complicated by the space limitations imposed by a well casing. The paper presents the design of PMB-AD modules, as well as their integration and testing as a part of a DHGC.

Research on combination of passive magnetic bearing and mechanical bearing for vertical axis wind turbine

Aiming at the “light wind start, light wind power generation” of vertical axis wind turbine, a new T-shaped radial passive magnetic bearing with high suspension characteristics is proposed. Passive magnetic bearings used in vertical axis wind turbines usually have small bearing capacity and difficult magnetization. The new T-shaped radial PMB can improve the radial bearing capacity, and the three magnetic rings all adopt simple axial magnetization. The new T-shaped radial PMB is combined with mechanical auxiliary bearing to form the suspension system of wind turbine. In the stable state, the suspension system can realize radial and axial stable suspension. The structure and working principle of the suspension system are briefly described. Through the finite element simulation, the characteristics of the new T-shaped radial PMB, the traditional double-ring PMB and the T-shaped PMBs are compared. Taking the high bearing capacity and high stiffness of the new T-shaped radial PMB as the optimization objective, the multi-objective optimization of the new T-shaped radial PMB was carried out by changing its geometric parameters (inner diameter, magnetization length and air gap). The research results show that: Under the same bearing capacity, the volume of the new T-shaped radial PMB is reduced by about 78.64%. Under the same volume, its bearing capacity increased by about 30.7%, and its stiffness increased by about 96.1%. After optimization, its radial bearing capacity increased to 101.38 N, and its stiffness increased to 202.76 N/mm.

Design methodology for monolithic layer radial passive magnetic bearing

Passive magnetic bearings (PMBs) are considered to be one of the economical and effective methods for levitating two surfaces in relative motion. This obviates the use of lubrication, provides zero wear, and negligible friction, thereby making the operation maintenance free. Due to these advantages, the modeling and design of the PMBs were given substantial importance in many studies. However, a well-defined designing procedure to achieve desired load carrying capacity for the given space constraints for the intended PMB application is yet to be established. Prior studies were performed on PMBs for achieving maximum load carrying capacity, but no design methodology was proposed that could facilitate easier design of a PMB in lesser computational time. In the present work, a very effective and a straightforward method is proposed to design a PMB for its paramount output. For this, dimensions of PMBs from the literature are considered for analysis and a set of equations are proposed for the determination of mean radius, axial length, and clearance for a given inner and outer radii of single layer PMBs. Finally, an equation is provided for estimating the load carrying capacity for the determined dimensions of PMB from the proposed design procedure. The effectiveness of the proposed methodology is demonstrated by considering the dimensions of PMBs from 10 literature.

Multi-objective optimization of stacked radial passive magnetic bearing

Modeling, design, and optimization for performances of passive magnetic bearings (PMBs) are indispensable, as they deliver lubrication free, friction less, zero wear, and maintenance-free operations. However, single-layer PMBs has lower load-carrying capacity and stiffness necessitating development of stacked structure PMBs for maximum load and stiffness. Present work is focused on multi-objective optimization of radial PMBs to achieve maximum load-carrying capacity and stiffness in a given volume. Three-dimensional Coulombian equations are utilized for estimating load and stiffness of stacked radial PMBs. Constraints, constants, and bounds for the optimization are extracted from the available literature. Optimization is performed for force and stiffness maximization in the obtained bounds with three PMB configurations, namely (i) mono-layer, (ii) conventional (back to back), and (iii) rotational magnetized direction. The optimum dimensions required for achieving maximum load without compromising stiffness for all three configurations is investigated. For designers ease, equations to estimate the optimized values of load, stiffness, and stacked PMB variables in terms of single-layer PMB are proposed. Finally, the effectiveness of the proposed method is demonstrated by considering the PMB dimensions from the available literature.

Magnetic Suspension with Motorization to Measure the Speed of Gravity

This work aims to design a magnetic suspension for an experiment to measure gravitys velocity. Such device must rotate two objects symmetrically with the greatest mass and largest radius as possible, at the speed of [Formula: see text], which means this device falls into the high-speed machines category. The guidelines and solutions proposed in this paper constitute a contribution to this class of engineering problems and were based on an extensive literature search, contacts with experts, the tutors and author’s experience, as well as on experimental results. The main solution proposed is a hybrid bearing that combines a radial passive magnetic bearing with an axial sliding bearing, here called MPS (Magnetic Passive and Sliding) bearing.

Development of Analytical Equations for Design and Optimization of Axially Polarized Radial Passive Magnetic Bearing

In the present research work, analytical equations have been developed for design and optimization of radial axial polarized passive magnetic bearing (PMB) with single layer for facilitating easy and quick solution, obviating the need of costly software. Seven design variables: eccentricity, rotor width, stator width, rotor length, stator length, clearance, and mean radius were identified as the main factors affecting the design and were thus considered in the development of analytical equations. The results obtained from the developed analytical equations have been validated with the published results. The optimization of the bearing design, with minimization of magnet volume as the objective function, was carried out to demonstrate the accuracy and usefulness of the developed equations.

Interaction magnetic force calculation of radial passive magnetic bearing using magnetization charges and discretization technique

Calculation of the interaction magnetic force between two ring permanent magnets with radial magnetization is presented in the paper. Such configuration corresponds to a radial passive magnetic bearing. The simple and fast analytical approach is used for this calculation based on magnetization charges and discretization technique. The results for interaction magnetic force obtained using proposed approach are compared with finite element method (FEM). The advantage of presented approach is its simplicity and time efficiency since only complete elliptic integrals of the second kind are used and other additional integrations are avoided in this calculation.

Second-Order Model of the Radial Passive Magnetic Bearing with Halbach's Array

In the paper is presented model of the passive magnetic bearing. The response of bearing is approximate by second order model. There are presented the damping and stiffness coefficient of suspension. The coefficients derived from Biot-Savards law, Ohms law and Lorenzs force. There is presented loop with molecular current as a model of magnet, final formula of damping and stiffness coefficients and static characteristic of passive magnetic bearing.

Study on axial unbalance mechanism of radial passive magnetic bearings and its effects

Study on axial unbalance mechanism of radial passive magnetic bearings and its effects

High Efficiency Radial Passive Magnetic Bearing

Passive magnetic bearing with Halbach array is presented in this paper. The array uses permanent magnets with radial and axial magnetization to augment the magnetic field on one side of the array and cancel it on the other side. The design of the bearing consists of ring-shaped magnets of 60x70 mm and 75x85 mm with different orientation of magnetization. The designed passive magnetic bearing has air gap of 2.5 mm, stiffness 129297 N/m and maximal value of load 200 N. The bearing ensures magnetic levitation and stabilization of rotor in a work point. The paper presents the design of the passive magnetic bearing as well as the experimental setup together with investigation results.

Mathematical model of radial passive magnetic bearing

Mathematical model of radial passive magnetic bearingIn the article a mathematical model of radial passive magnetic bearings applicable to ocean engineering units has been presented. The application of the bearings in ship thrusters should increase durability of propulsion systems and give lower maintenance costs. The rotor of thruster's electric motor is suspended in magnetic field generated by radial passive magnetic bearings. However the maintaining of axial direction of the rotor must be controlled with electromagnets equipped with a high-dynamic controller. The risk of application of the magnetic bearings results from very low stiffness of the unit in comparison with rolling bearings. Also construction of the bearing should be different due to gyroscope effect and high forces generated during ship manoeuvring. The physical model performs correctly if electromagnets are controlled properly; and, technological problem with sealing system seems more significant than power supply to electromagnets winding. The equations presented in the article are necessary to build algorithms of a digital controller intended for on-line controlling magnetic bearing in axial direction.

HALBACH STRUCTURES FOR PERMANENT MAGNETS BEARINGS

This paper is the third part of a series dealing with permanent magnet passive magnetic bearings. It presents analytical expressions of the axial force and stifiness in radial passive magnetic bearings made of ring permanent magnets with perpendicular polarizations: the inner ring polarization is perpendicular to the outer ring one. The main goal of this paper is to present a simple analytical model which can be easily implemented in Matlab or Mathematica so as to carry out parametric studies. This paper flrst compares the axial force and stifiness in bearings with axial, radial and perpendicular polarizations. Then, bearings made of stacked ring magnets with alternate polarizations are studied for the three kinds of polarizations, axial, radial and perpendicular. The latter correspond to Halbach structures. These calculations are useful for identifying the structures required for having great axial forces and the ones allowing to get great axial stifinesses.

A large scale approach of bulk HTS to the electric utility area

On the basis of a novel industrial-like YBCO seedless functional melt texture grain alignment process, various HTS devices for superconducting magnetic bearings (SMB) and high-current leads for transport and limiting purposes are fabricated. Critical shielding currents of 30 kA/cm/sup 2/ at 77 K are utilized to construct radial-passive magnetic bearings for 20 kg loads or to suspend and spin a O 4 cm rotor safely to 120000 rpm. Stiffnesses between 40 to 140 N/mm are measured. Multi-grain YBCO rods up to 20 cm length are tested for more than 6 kA/cm/sup 2/ transport currents. The connections to the copper braids are improved to less than 0.4 micro-ohm at 1000 Amperes and 77 K. The experiments show the practical potential of melt textured YBCO with macroscopic orientation of the grain structure for electric power purposes.