Fig 8 - uploaded by Changsheng Zhu
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Failure phenomenon caused by narrow pulses loss Considering three kinds of setting deviation of the threshold voltage and the narrow pulses loss at the same time, power amplifier current waveforms were shown in Figure 9.
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The switching power amplifiers with high efficiency are often required in active magnetic bearings, but they have some problems due to the switching process. In fact, the control current in the switching power amplifiers is superimposed with a considerable number of higher harmonics. The three-level PWM modulation was proposed to obtain smaller cur...
Context in source publication
Context 1
... the same as the theoretical analysis, when U err1 =U err1 and U err1 >U err2 , there is no current waveform distortion; when U err1 <U err1 , The current waveform becomes trapezoid. The effect of the narrow pulses loss on current waveform is shown in Figure 8. The periods of three-level current ripple is integer multiples of switching frequency which was the same as the results of experiment as shown in figure 6(b). ...
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Citations
Active magnetic bearings (AMB) have gained significant attention in recent years due to their superior performance in various industrial applications. One crucial component of an AMB system is the discrete power amplifier, which plays a vital role in driving the magnetic coils and controlling the position and stability of the rotor. This article provides a comprehensive review of power amplifier technologies in combination with the H bridge converter and feedback sensing circuits used in AMB. In addition, it discusses the design considerations, operational principles, and performance metrics of power amplifiers. Finally, challenges and potential future directions in power amplifier technology for AMB along with conclusions are highlighted.
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Magnetic bearing system of five DOF needs five H-bridge switching power amplifiers, in order to enhance integrated level and power density of the power amplifier, a five-phase six-leg topology was adopted in this paper. A hybrid current control method was introduced, in which the control of neutral leg and phase leg was independent. In this control strategy, the control strategy of the neutral leg was the improved maximum current error modulator, it could reduce the couple of five output currents to the largest extent by adding a current error polarity judgment module. The control strategy of other legs was an improved sample-hold modulator, which can satisfy different load conditions varying in a wide range. The simulation and experiment results indicate that the five-phase six-leg switching power amplifier based on the new hybrid current control method has the advantages of low current ripple, fast dynamic response, least association with load parameters, high integrated level, simple logic interfaces and so on.
The current mode switching power amplifier is an essential component in magnetic bearing system which works in the nonlinear switching state. At present, the characteristics of the power amplifier can be revealed partially by establishing first order inertial element model. In order to accurately investigate the actual working characteristics of the current mode power amplifier, a precise mathematical model of switching power amplifier is proposed based on the circuit principle and Fourier series analysis method. In the analysis of the current forming principle for three-level Pulse Width Modulation (PWM) power amplifier, the load coil voltage is deduced by Fourier series method. The steady state current model and ripple current model are established, respectively. Compared with the model simulation and experiment, the results show that the characteristics of the ripple current, steady state and dynamic state are basically consistent. We found that the model predictions results are in excellent agreement with the actual experiments data, indicating the numerical simulations model is feasible and effective for the design of power amplifier system.
This paper presents the concept and the practical implementation of a switch-mode power driver for the use in Active Magnetic Bearings (AMB). The switch-mode driver consists of a full-bridge capable of operating in 2-level, 3-level, or phase-shifted PWM mode. An optimal digital current-programmed mode controller lays out the foundations to a proximate-optimal, robust, large-signal dynamic response of the system under extreme cases of loading and parameters variations. In particular, the developed power driver is capable of following the desired reference for large inductance variations (due to displacement). The power stage combines a newly developed, efficient, passive-based current sensor that is capable of sensing bi-directional and near-zero currents, while being robust to external disturbances and maintaining simple and efficient structure. Performance evaluation of the power driver has been verified experimentally on a closed-loop design for a single-axis AMB platform using a dual channel prototype, controlled using a single 16-bit, low-cost microcontroller.
