Dual‐mode power drive for active magnetic bearings

Abstract

A compact-design hybrid power amplifier for Active Magnetic Bearing (AMB) units, named as Dual Cooperative Drive Circuit (DC 2), is designed and verified by intensive experiments. DC 2 can operate under dual mode: either Digital Driving Mode (DDM) or Analogue Driving Mode (ADM). By taking advantages of the complementary cooperation between DDM and ADM, the proposed DC 2 manifests its superiorities mainly in three aspects. (i) Compared to a traditional 2-level 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 DC 2. (iii) DC 2 can provide high current slew rate so that the response of AMBs is pretty 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 DC 2 is particularly suitable to be complied with digital controllers and Digital Signal Processors since the commands or drive sequences are all in Direct Current manner.

Power Amplifiers and Their Feedback Mechanisms for AMB—A Comprehensive Review

“…Unlike conventional mechanical bearings that rely on physical contact between components, AMB employs electromagnetic forces to suspend and control the position of a rotor. Applications include annular suspension and pointing systems [3], non-contact gyros, high-speed compressors [4], diary industries, high precision [4], machine tools, blood pumps [5][6], artificial heart pumps [7], [8], turbomolecular pumps [9], jet engines, bearing less motors [10] [11] etc. Initially, the rotor, which remains non-rotating, is elevated into the air by the AMB, effectively functioning as a pure bearing.…”

“…An AMB stator typically consists of two opposing electric coils, though four coils are common for radial bearings [4].…”

“…Researchers in [18] investigated the factors influencing the inherent current ripple in SPA, while a dual-mode power drive hybrid power amplifier was designed in [4] to simultaneously reduce current ripple and enhance the current response rate, considering both transient and steady states in the AMB system. In [19], authors proposed a current predictive control method based on proportional-differential current-sensing resistor networks, which improved current tracking accuracy and reduced current ripple in SPA.…”

“…The large-signal path, responsible for generating significant driving forces, employs a switching amplifier for higher efficiency and power handling capabilities [80].…”

Evaluation of Switching Power Amplifier Topology for Active Magnetic Bearings

“…Regarding the accuracy characteristic of the output current of SPAs, Xin Cheng et al [6] studied the main factors affecting the inherent current ripple. To reduce the current ripple and improve the current response rate simultaneously, Hsin-Lin Chiu et al [7] designed a dual-mode power drive as the hybrid power amplifier under the consideration of both the transient and steady state of the AMB system and showed its superiorities in their experiment. Yuan Ren et al [8] proposed a current predictive control method based on proportional-differential current-sensing resistor networks to solve the problem of digital control delay in traditional linear predictive control in SPAs, which improved the current tracking accuracy and reduced the current ripple.…”