| In comparison with the conventional rolling element or journal bearings, active magnetic bearings( AMB), which use controllable electromagnetic force to support freely a rotor, are being widely used in rotating machinery. In the AMB system, a power amplifier which provides magnetic coil with exciting current to produce electromagnetic force, is one of the main components.The paper firstly classifies power amplifiers, and then studies the operating principles and characteristics of linear power amplifiers and switching power amplifiers. By comparing with advantages and disadvantages of various modulate techniques used in the switching power amplifiers at present, two-level PWM modulate switching power amplifier which integrates inner current-loop is designed and debugged. Characteristics of PWM power amplifier are also analyzed, and the results show that they fundamentally meet the design requirements of an AMB.Based on TMS320F240 which have fast operating capability and the event manager with flexible control capacity, hardware design project of three-level PWM modulate switching power amplifier is proposed and partially verified experimentally.On basis of various realizable technologies of high-power amplifier, their feasibility used in the AMB system is analyzed and designing guidance is given. Improved projects of two-level PWM modulate switching power amplifier and three-level switching power amplifier are also given. |
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