Mechanism Analysis of Eddy-Current Effects on Switching Power Amplifier of a Nonlaminated Magnetic Bearing

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.