| In comparison with the conventional rolling element or journal bearings, active magnetic bearings (AMB's), which use 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 studies the operating principles and characteristics of switching power amplifiers. Mechanical parameters are introduced in the AMB coil's inductance to indicate the dependence of the current harmonics on mechanical parameter, and the influence of mechanical parameters on current harmonics of the switching power amplifiers is analyzed. By comparing with advantages and disadvantages of various modulate techniques used in the switching power amplifiers at present, a PWM modulate technique is adopted due to its practicality. Considering the difficulty to design the control logic's hardware of three-level voltage switching power amplifier, a hardware design project of three-level voltage switching power amplifier is proposed and partially verified experimentally based on TMS320F240 which have fast operating capability and the event manager with flexible control capacity. Moreover, the two-level and three-level switching power amplifiers are designed and debugged. A complete hardware design from front input to H-bridge output is also presented. On basis of various realizable technologies of high-power amplifier, their feasibility used in the AMB system is analyzed and designing guidance is given.The two-level voltage power amplifier and the three-level voltage power amplifier are designed and results show that they fundamentally meet the design requirements of an AMB. |
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