Experimental Investigations on Self-Bearing Motors with Combined Torque and Electrodynamic Bearing Windings (original) (raw)
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The magnetic bearing is an electro-mechanical device that maintains the rotor of an equipment magnetically levitated. Besides allowing for a contact less working condition, resulting in a system without mechanical wear, this device presents other advantages, such as self-balancing, vibration control, self-monitoring, possibility of equipment encapsulation and high operation speed, with high reliability and reduced maintenance. Taking these advantages into account, magnetic bearings are becoming technologically competitive in many applications such as turbo-generators, pumps, compressors, fabrication machines, gyroscopes, centrifuges etc. It should be realized that since the absence of friction eliminates the need of lubrication, the magnetic bearings are ideal for airspace applications and for radioactive environments. Moreover, due to this same characteristic, it is an energy-saving device, which is, perhaps, the main reason for its utilization in new equipments. In order to gain a better understanding of this technology, a prototype of an integrally levitated electrical motor has been developed. The mechanical, magnetic and electric conceptions of the bearings have been already described in previous works, including the mechanical engineering considerations related to the design, fabrication and mounting of the magnetic bearings on the equipment. In this work, the successfully design and implementation of the displacement controllers are described. Simulations and experimental results show the static and dynamic performance of the bearings.
Sliding-mode control design of a slotless self-bearing motor
We encourage authors to share their published articles on social network and repositories, such as SSRN, arXiv, academia.edu, ResearchGate, RePEc, Google Scholar, Mendeley, Zenodo, Archive, Slideshare, Linkedin, Facebook, etc., 2022
Scientists have explored and are studying a slotless self-bearing motor, an electric motor with a magnetically integrated bearing function. As a single actuator, it can provide both levitation and rotation. This article will show a slotless self-bearing motor with a stator that does not have an iron core but six-phase coils. A permanent magnet and an enclosed iron yoke make up the rotor. To regulate the rotational speed and radial location of the rotor, magnetic forces created by the interaction between stator currents and the magnetic field of permanent interest are investigated. This research also includes a slotless-bearing motor mathematical model and control approach. This motor is investigated by combining an AC motor with a magnetic drive to achieve the essential design criterion and low cost. The magnetic force and moment characteristics are theoretically analyzed, and a control technique is proposed. Sliding-mode control (SMC) is a control method that is simple, effective and utilized to serve the control system for approaching the reference value, as stated in this study. It's also commonly used to manage the motor's position and speed. The findings were built and evaluated using MATLAB/Simulink confirmed analytical results to prove the recommended control approach.
Mechanical Engineering Journal
In permanent magnet motors, the presence of rotor eccentricities can alter the airgap field distribution. This results in parasitic radial detent forces that can be reduced by connecting the stator phases in parallel. As a consequence, currents are passively induced in the windings when the rotor spins in an off-centered position, yielding balancing electrodynamic forces. Specific models were developed to predict these forces, but their complexity can be prohibitive. Therefore, this paper proposes to study the effect of the rotor off-centering in permanent magnet motors using a simpler model developed for electrodynamic bearings. This model consists in a linear differential equation with only four parameters that depend neither on the spin speed nor on the rotor position. As an illustration, the paper applies this model to the study of a high-speed, slotted permanent magnet motor. To support this, the main hypotheses of the model are validated in this particular case. Then, the centering electrodynamic forces in a staticeccentricity configuration are predicted using the model and compared to finite element simulation results. Finally, a preliminary study showing the impact of the width and permeability of the stator teeth on the centering force is performed.
Design and measurement of a passive thrust magnetic bearing for a bearingless motor
IECON 2013 - 39th Annual Conference of the IEEE Industrial Electronics Society, 2013
The design and construction of a permanent magnet thrust bearing for a bearingless motor is presented and a measurement technique is proposed to characterize the bearing. Optimal design of a bearingless motor requires the machine designer to be aware of the axial bearing's performance under simultaneous axial and radial displacement. A simple, low-cost test setup which requires only two single-axis load cells is proposed and evaluated to make these measurements on the magnetic bearing stator. The measurement data are found to be in reasonable agreement with finite element calculations and to satisfy Earnshaw's theorem, where the sum of stiffnesses in the three axes must be zero. The measurement technique displayed good test-retest reliability, with repeated radial force data having an average standard deviation of 2.1% for radial displacements greater than 0.5 mm and axial force data having a typical error of 0.9%.
Analytical Model of Current-Force Characteristics of a Combined Radial-Axial Magnetic Bearing
In today's industry high-speed and high-power-density drives are attracting much interest, e.g. for applications with mesoscale gas turbine generator systems or turbocompressors for fuel cells. In all high-speed drive systems the bearing technology is a key component. Therefore, this paper presents the analysis of an active magnetic bearing suitable for a permanent magnet machine, being part of a high-speed electrical drive system. The analysis has its focus on the detailed characterization of the magnetic forces, the coupling between the different axes and the verification of the theoretical considerations by means of 3D-FEM simulations. To understand the behavior of the bearing forces is needed to implement the position control to the prototype of the bearing system, which already has been built.