Performance Comparison of Tri-level Switching AMB Power Amplifiers Based on Different Current Sensors and Control Methods

Active magnetic bearings are advanced bearing components for High Temperature Gas-cooled Reactors. As an important part of active magnetic bearings, switching power amplifiers are designed to accurately convert a command signal to a real bearing coil current. Current ripples of the power amplifiers can be reduced effectively based on different tri-level control methods. Their performances are different. Even when the same control method is used, the performances of amplifiers using electrical circuits with different hardware components are different. To reduce current ripples of amplifiers, the performance of amplifier circuits with different current sensors and different control methods were studied. With the same control method, three kinds of current sensors were used in a power amplifier and their performances were compared. It was shown that hardware delay caused the performance difference. With the same current sensor, a tri-level Sampling-Hold method and a Pulse-Width Modulation (PWM) method were used to control the same amplifier driver. The accuracy of the tri-level PWM amplifier was better. The reason for the performance difference between the two methods was discussed. The experimental results were provided.