Have you ever observed the top of an electrolytic capacitor? Many electrolytic capacitors have a cross at the top. Is this design for aesthetic purposes? Actually, it is not. This is the design of the capacitor for safety reasons. When an electrolytic capacitor is working, it will get hot for a long time because of the liquid electrolyte inside. Then with the accumulation of heat, some capacitors will expand or bulge open. When the capacitor quality is poor, the voltage is too high over the capacitor's withstand voltage value leading to breakdown, or the polarity is wrongly connected during installation, the capacitor can easily explode and cause danger. For this reason, capacitors are designed with insurance devices and cross-shaped grooves on the top, which can release pressure when the pressure is high and the top is cracked to avoid explosion.

In addition to the cross groove, some capacitors in order to compare the pressure generated by the explosion, will be designed trident-shaped groove, or K-shaped groove,. As shown in the figure below, a certain pressure is reached, the K-shaped explosion-proof groove can be arched away to avoid an explosion.