A novel permanent magnet bias hybrid thrust magnetic bearing with extremely simple structure for high-speed rotating machinery

This paper presents a novel permanent magnet (PM) bias hybrid thrust magnetic bearing (HTMB), which can be used to replace the traditional thrust magnetic bearings (TMBs) for high-speed rotating machinery. By adding two PM rings and by reducing the number of the control coils by half, this HTMB eliminates the bias current, reduces the number of amplifiers, and minimizes the magnetic bearing’s structure complexity and power consumption. The analytical modelling method of the HTMB is presented in this paper. Mathematical models for calculating the magnetic force capacity and the stiffnesses of this bearing are derived as simplified formulae, which can be used for the design, analysis, and control of this bearing. Electromechanical characteristics of the HTMB are analyzed, which is compared to the traditional TMB to demonstrate the advantages of the HTMB. The prototype of the HTMB is designed, analyzed, and fabricated, whereas, the 2-D FEM is used to verify the design and the analytical model. Finally, an experimental setup is constructed and tested. The analytical and experimental results indicate that the proposed novel topology of this HTMB is feasible and the presented analytical model is accurate.

Development of an axial-flux self-bearing motor using two permanent magnet attractive type passive magnetic bearings

This paper introduces an axial-flux self-bearing motor (ASBM) using two permanent magnet attractive type passive magnetic bearings (PMBs). The ASBM provides both functions of a disc motor and thrust magnetic bearing, and controls motor torque and axial force by single rotational magnetic flux. The PMB consists of a cylindrical permanent magnet and an iron shaft with conical edge, and it supports the rotor in radial directions. This motor has a simple structure and control system, and it is possible to reduce the size and cost. In this paper, the structure and control method are introduced, and the results of levitation and rotation tests whose non-contact rotation speed was achieved up to 1,500 rpm are shown.

A Novel Integral 5-DOFs Hybrid Magnetic Bearing with One Permanent Magnet Ring Used for Turboexpander

We propose a novel combined five-degrees-of-freedom (5-DOFs) hybrid magnetic bearing (HMB) with only one permanent magnet ring (PMR) used for turboexpanders. It has two radial magnetic bearing (RMB) units; each has four poles and one thrust magnetic bearing (TMB) to control 5-DOFs. Based on one PMR, the bias flux of the two radial magnetic bearing units and the one thrust magnetic bearing unit is constructed. As a result, ultra-high-speed, lower power loss, small size, and low cost can be achieved. Furthermore, the equivalent magnetic circuit method and 3D finite element method (FEM) are used to model and analyze the combined 5-DOFs HMB. The force-current, force-position, torque-coil currents, the torque-angle position, and the stiffness models of the combined 5-DOFs HMB are given. Moreover, its coupling problems between the RMB units and the AMB unit are also proposed in this paper. An example is given to clarify the mathematical models and the coupling problems, and the linearized models are proposed for the follow-up controller design.