Application of Active Magnetic Bearing in Waste Heat Generator

Aiming at the problems of low efficiency, high cost and large volume of the traditional waste heat power generation equipment, a waste heat generator equipped with the 5-DOF (5-degree of freedom) active magnetic bearing for Organic Rankine waste heat generation system was designed. Firstly, based on the rotor diameter limit and maximum bearing capacity requirements, the structural forms of radial and axial magnetic bearings were determined. Furthermore, the dimensions and performance parameters of magnetic bearings were calculated and checked by one-dimensional magnetic circuit model and two-dimensional finite element analysis. Secondly, in order to ensure the stability margin of the magnetic bearing, a three-level PWM (pulse-width modulation) power amplifier was used to reduce the output current ripple, and an incomplete differential PID controller incorporated with unbalance compensation were used to realize the 5-DOF stable suspension. Finally, the waste heat generator equipped with magnetic bearing was applied to the actual customer site. The reliability of the waste heat generator was verified from three dimensions of stability margin, bearing capacity and shaft peak-to-peak value. The field test results show that the waste heat generator system has operated stably and reliably in all operation conditions, and can achieve full-power generation and long-term operation. The sensitivity function of the magnetic bearing system is less than 12 dB, and the peak-to-peak vibration value of the rotor of the waste heat generator is less than 53 μm, which meet the long-term stable operation requirements of ISO14839. The maximum axial bearing capacity reaches 3 600 N, which meets the requirements of actual working conditions. Copyright ©2022 JOURNAL OF SOUTHWEST JIAOTONG UNIVERSITY. All rights reserved.