Damage and failure of electrolytic capacitor in power supply (II)

The failure, complete leakage or pulping caused by the disappearance of electrolytic capacitor capacity is the most difficult to distinguish and maintain after the failure of the capacitor in the power supply, because the measurement of capacitance devices, using the multimeter to test all normal, but after the capacitance is installed on the circuit, the capacity of the capacitor is completely lost, this is the most difficult to repair the soft reason in the circuit. One of the obstacles is that components can not withstand voltage, and the existence of a voltage can easily disappear.

Types of explosion slurry are classified into two categories: input capacitor explosion slurry and output capacitor explosion slurry. For input capacitors, it is a capacitor which is large in volume, large in size and high in rated voltage. It filters the received current. The input capacitance is related to the input current of the power supply and the quality of the capacitor itself. Excessive burr voltage, high peak voltage, current instability and so on make the capacitor overcharge and discharge too frequently, the capacitance in this kind of working environment for a long time, the internal temperature rises very quickly. Explosion will occur if the limit of the vent is exceeded. For output capacitors, the current adjusted by the power module is filtered and stored. The current has been filtered for a relatively stable time, and the possibility of bursting is relatively small. However, if the ambient temperature is too high, the capacitance is also prone to burst. There are many reasons for the electrolytic capacitor to burst the pulp, such as the current is greater than the allowed wave current, the use voltage exceeds the working voltage, the reverse voltage, the frequent charge and discharge and so on. But the most direct reason is the high temperature. We know that an important parameter of capacitance is the temperature resistance value, which refers to the boiling point of the electrolyte inside the capacitor. When the internal temperature of the capacitor reaches the boiling point of the electrolyte, the electrolyte begins to boil, the pressure inside the capacitor rises, and the pulping occurs when the pressure exceeds the limit of the vent. Therefore, temperature is the direct cause of capacitance explosion. The design life of capacitance is about 20 thousand hours, and the influence of environmental temperature is also great. The service life of the capacitor decreases with the increase of temperature. The experiment proves that the life of the capacitor will be reduced by half if the ambient temperature rises by 10 degrees. The main reason is that the temperature accelerates the chemical reaction and causes the medium to degenerate with time. In order to ensure the stability of the capacitor, the capacitor must be tested for a long time in the high temperature environment before the plug-in board. Even at 100 degrees, high quality capacitors can work for thousands of hours. At the same time, the life of the capacitor mentioned is that the capacitance of the capacitor will not exceed 10% of the standard range during the use of the capacitor. Capacitor life refers to the problem of capacitance, rather than burst after the arrival of design life. Just can't guarantee the capacitance standard of capacitance design. Therefore, in a short period of time, the normal use of the plate capacitor will explode slurry, which is the quality of capacitor. In addition, the abnormal usage may also cause capacitor explosion.