Filtering Suppression for Large Peak Conducted EMI From High-Speed Axial Flow Fan

An axial flow fan is widely used for heat dissipation in aviation and aerospace electronic devices. Due to its frequent speed regulation to adapt to the change in heat load, the fan will produce significant electromagnetic interference (EMI). This article presents a conducted EMI filtering suppression for a high-speed pulsewidth modulation axial flow fan. The conducted EMI of the fan is first measured to identify some large peak voltages much exceeding the specified limitation; then, a time-domain circuit simulation model of the fan driving system is created to predict the insertion loss of the designed filter. By analyzing the mechanism of conducted EMI and its propagation path, the dominant parameters are identified, and the topology structure and key parameters of the filter are optimized. The results show that the insertion loss of filter suppression for EMI is improved from the predicted 5.65 dB to the measured 50.1 dB without affecting the effective signal.