High Efficiency Linear Power Amplifier for Active Magnetic Bearings

To improve the overall efficiency of a transconductance amplifier loaded by the high inductance and low resistance typical of the magnetic bearing coils, a modified class G amplifier has been de veloped. A simple theoretical characterization has been used to provide some diagrams to optimize the power efficiency as a function of a non constant load such as that due to a rotor unbalance. Experimental results are reported showing a more than satisfactory agreement with the developed theory.