Fuse cutouts fuse arc extinguishing measures
When the fused core fused, the fuse will immediately produce an arc. This does not count, the fused core fused metal vapor generated after the more intensified the intensity of the arc, making the arc burning more intense.
Let’s look at the circuit diagram in the figure for normal operation, when the fuse is operating normally, the current of the system I = E/R, and the voltage drop of the fuse Uh = 0. This point is located at the E/R point on the current axis. If the fuse is completely disconnected, the current is equal to zero at this time, and the voltage across the fuse is E. This point is located at point E on the voltage axis. We connect point E with the point E/R with a straight line, which is called the DC load line. We look at Figure 7 of the fuse protection fuse instantaneous circuit diagram, the fuse has been fused in the figure, the arc in the fused score. The arc voltammetric curve has a negative resistance, that is the greater the current flowing through the arc, the lower the arc voltage drop Uh, the higher the temperature of the arc. We superimposed the arc voltammetric curve H1 on the DC load line, see Figure. We see that the arc voltammetric curve and DC load line have two points of intersection, the stable burning point of the arc must be in point 1 or point 2. Theoretical and practical evidence, the stable burning point of the arc is located in point 2. arc is very nasty, it will burn the fuse, and may affect other appliances because of the arc ejected, so we expect to quickly extinguish the arc. From Figure 7 we see that to extinguish the arc can increase the resistance R, so that the current axis of the E / R point to the left, the DC load line from the arc voltammetric characteristic curve, the arc is naturally extinguished; at the same time, we can also stretch the arc length of the arc, so that the arc temperature drops rapidly, resulting in the arc extinguished, which is the method of extinguishing the arc fence. For the fuse, it has a special arc extinguishing method, which is the use of fine sand around the fuse core copper piece. When the arc appears, the sand immediately buried fractures, the arc also cooled and extinguished. Therefore, the fused core filled with fine sand has a very special ability called current-limiting ability.