Complementary Cooperation of Dual Power Circuits to Drive Active Magnetic Bearings

Abstract

A compact-design hybrid power amplifier for AMB (active magnetic bearing) units, named as dual cooperative drive circuit (DC2), is designed and verified by intensive experiments. DC2 can operate under dual mode: either digital driving mode (DDM) or analog driving mode (ADM). By taking advantages of the complementary cooperation between DDM and ADM, the proposed DC2 manifests its superiorities mainly in three aspects: (i) Compared to a traditional 2-level PWM (pulse width modulation) drive circuit, the improvement degree of reducing the amplitudes of current ripples is up to 62%. (ii) By taking advantages of mutually complementary cooperation between DDM and ADM, the steady-state errors of output current, which is exerted to the coils of AMBs, can be much reduced by DC2. (iii) DC2 can provide a high-current slew rate so that the response of AMBs is fast and quick enough to regulate the high-speed rotor back to the neutral position within a very short time period below 0.40 ms. In addition, the proposed DC2 is particularly suitable to be compliant with digital controllers and DSPs (digital signal processors) since the commands or drive sequences are all in DC (direct current) manner.

Study on the Effect Mechanism of MRD to Rotor System

“…Active control (e.g., controllable squeeze film damper [5,6], electromagnetic bearings [7,8], shape memory alloy actuator [9], piezoelectric actuator [10][11][12]) can overcome the limitations of the passive control through adjusting its parameters to adapt to the change of the external conditions. As a kind of intelligent material, magnetorheological fluid (MRF) can rapidly change from liquid state to quasi-solid state under the action of an external magnetic field, and the change process is continuous, controllable and reversible.…”