Online Noninvasive Technique for Condition Monitoring of Capacitor in Linear Power Supplies

Linear power supplies (LPSs) are widely used in fields including measurement systems, radiofrequency systems, medical applications, nuclear power plants, and spacecraft electronics. Electrolytic capacitors are used in a variety of devices because of their small size, low cost, and large capacity. During the use of electrolytic capacitor, it is very common for the capacitance (C) to decrease and its equivalent series resistance (ESR) to increase, which are typical indicators of capacitor degradation. Electrolytic capacitors are both the weak link and the core component of the LPSs and play a vital role in determining the LPSs lifetime. Under the power frequency condition, the power frequency transformer plays a role in isolation and voltage reduction in the LPSs. The input and output signals of the LPSs are used for condition monitoring of capacitor, and the existence of transformer increases the difficulty of the online noninvasive technique of LPSs. The online noninvasive technique for condition monitoring of capacitor in LPSs proposed in this article can be solved only by using the input current, the magnetizing current, the input voltage, and the load current. Effect of temperature on C and ESR values is incorporated for accurate determination of the parameters of capacitor. The effectiveness of the proposed method is verified through simulations and experiments, and the data obtained are consistent with the results measured using an LCR meter.