Causes of noise in film capacitors
Today’s power grids contain a variety of high-order harmonics, and they mainly exist in the form of current, and capacitors just like to be courteous with it. If someone nearby uses electric welding, or high-power electrical appliances with thyristor phase modulation, the electrodes of the capacitor It will vibrate and make a sound. In addition, the harmonic current has a great destructive effect on the capacitor. The electrode of the CBB capacitor is a metal film sprayed on the film. Under the action of the instantaneous high current, the part near the two ends is likely to generate ohmic heat, which causes the film to melt and cause a short circuit. Capacitors have the ability to self-heal against short circuits, but after self-healing, the ESR will become larger, making it easier to generate heat, a vicious circle, and will quickly fail completely.
Due to the low thermal conductivity of the film, the external surface temperature rise cannot be used to judge the internal instantaneous local temperature rise. Therefore, it is best to check the manufacturer’s specifications. The surge current should be limited. The unit should be the current time product, such as by second, Wait in milliseconds. It is also possible that the current is too large and it is not caused by the current limiting resistor. The xuansn capacitor manufacturer has a professional production team, the pass rate must be higher than 99%, and the quality stability of the same batch of capacitors must be controlled within 3%.