| Two kinds of novel switching power amplifiers for magnetic bearings are studied in this paper separately using 3-leg and 4-leg topologies as main power circuits. These two topologies have smaller size and higher intergration rate than traditional power amplifiers for magnetic bearings. They can also be used as ordinary three-phase inverters, which overcome the drawback of traditional power amplifiers which have only one function. In this paper, three-leg switching power amplifier is controlled by SVPWM. The principle of SVPWM is discussed in detail and three kinds of switching pattern of SVPWM are analyzed and compared. Node Potential Modulation, a new control method based on the characteristics of 4-leg power amplifier, is proposed. This method has the virtues of simple structure and is easy to realize, having the same effect as SVPWM. The 3-leg switching power amplifier and the 4-leg power amplifier both have the advantages of small current ripple and high utilization ratio of voltage. Prototypes of 3-leg and 4-leg switching power amplifiers controlled by DSP are constructed based on emulation models. Simulation results and experimental results validate the high quality of the novel power amplifiers.
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