Abstract
For thrust magnetic bearings (TMB), the stators and thrust disks are commonly made of nonlaminated material. Therefore, eddy currents are inevitable in solid ferromagnetic cores. However, the mechanisms of eddy-current effects on switching power amplifiers have never been investigated. Firstly, the fractional-order model of effective reluctance of a nonlaminated TMB is built. And the time domain solution of current ripples of switching power amplifiers is calculated. Then we define the effective inductance and present the equivalent circuit of current drive mode. Through model reduction, the main impact factor of eddy currents is found, and the simplified model as well as simplified equivalent circuit is obtained. Furthermore, the effects of eddy currents on two current control modes and control parameter design are analyzed. Through finite element method (FEM) and experiments, the established models are verified, and the current tracking performance is compared between laminated and nonlaminated TMB with different control parameters, which demonstrates the theoretical results.
Highlights
Active magnetic bearings (AMB) are attractive options for rotor shaft support because they offer contactless operation, which leads to high power density, high efficiency and low maintenance demand [1], [2]
In order for small eddy current losses, lamination configuration has been commonly used in radial magnetic bearings (RMB)
It can be concluded that, since for smaller values of effective inductances derived from eddy currents, the current tracking rates of nonlaminated thrust magnetic bearings (TMB) are improved
Summary
Active magnetic bearings (AMB) are attractive options for rotor shaft support because they offer contactless operation, which leads to high power density, high efficiency and low maintenance demand [1], [2]. Based on the principle of effective reluctance, an accurate analytical model including eddy current effects and leakage effects was proposed for a 3-DOF magnetic bearing [10], and an optimal design method with multi-objective of minimum length and air friction loss was presented in [11]. Zhou and Li [14] extended the previous works and examined the modeling of a solid-core AMB under current drive as well as voltage drive They determined the effects of eddy current on system dynamics. The mechanisms of eddy-current effects on switching power amplifiers are researched in this paper. Rapidity and precision performance of switching power amplifiers is analyzed with consideration of eddy-current effects in this paper. Effects of eddy currents on current ripples are analyzed
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