As commonly used forced convection air cooling devices in electronics, cooling fans are crucial for guaranteeing the reliability of electronic systems. In a cooling fan assembly, fan bearing failure is a major failure mode that causes excessive vibration, noise, reduction in rotation speed, locked rotor, failure to start, and other problems; therefore, it is necessary to conduct research on the health assessment of cooling fan bearings. This paper presents a vibration-based fan bearing health evaluation method using comblet filtering and exponentially weighted moving average. A new health condition indicator (HCI) for fan bearing degradation assessment is proposed. In order to collect the vibration data for validation of the proposed method, a cooling fan accelerated life test was conducted to simulate the lubricant starvation of fan bearings. A comparison between the proposed method and methods in previous studies (i.e., root mean square, kurtosis, and fault growth parameter) was carried out to assess the performance of the HCI. The analysis results suggest that the HCI can identify incipient fan bearing failures and describe the bearing degradation process. Overall, the work presented in this paper provides a promising method for fan bearing health evaluation and prognosis.

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The 170 GHz gyrotron presented in this article has an operating voltage of 75 kV and a beam current up to 45 A, which requires the cathode emission temperature to reach above 1000°C. At such a high temperature, it is bound to cause the cathode of the electron gun to undergo thermal expansion and generate a certain amount of deformation, which may cause a large change in the performance parameters of the electron gun. This article uses thermal analysis simulation software ANSYS Workbench and COMSOL Multiphysics to perform thermal analysis processing on the electron gun. The thermal analysis results show that the temperature difference of the magnetron injection gun (MIG) cathode emission band is 4.6°C, and the total deformation is about 0.054 mm. The magnitude of the deformation is within an acceptable range and has little effect on the performance of the MIG. Comparing the thermal analysis results obtained by the two software, the simulation results agree well.

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