This paper proposes a drive circuit for single-phase brushless direct current (BLDC) fan motors to reduce their acoustic noise. First, the torque ripple of a single-phase BLDC motor is analysed theoretically. Then, a drive circuit that is capable of regulating the DC-link voltage during commutation to weaken the negative effect of current lag is proposed to reduce the acoustic noise of single-phase BLDC fan motors. Furthermore, the characteristics of the proposed drive circuit are discussed theoretically using a deduced analytical model of the proposed drive circuit. Additionally, simulations based on the finite element method and experiments are performed. The torque ripple and acoustic noise generated by the conventional and proposed drive circuits are compared. The simulation results show that the torque ripple is reduced by 16.1% when the proposed drive circuit is used, and the experimental results illustrate that the acoustic noise generated by the second harmonic of the torque ripple is reduced by 7.3%. Ultimately, the effectiveness of the proposed drive circuit is verified.
The composite material flywheel rotor of a flywheel energy storage system (FESS) has a low natural frequency. When the system suffers from noise interference, the magnetic bearing generates a force with the same frequency as the natural frequency and causes vibration to occur. Thus, it is necessary to suppress the natural vibration of the magnetic suspended (MS) FESS. The LMS adaptive notch filter is generally adopted for vibration suppression. The vibration suppression performance of the system is different when the insertion position of the notch filter is different. This paper analyzes the influence of the notch filter in different insertion positions of the control system. Through the transfer function from noise to magnetic bearing force, theoretical analysis of the influence of different positions of the notch filter is performed. Corresponding experiments are performed in a 500 kW MS FESS prototype. The theoretical analysis is verified experimentally.
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