Definition of IH and IT by self-recovery fuse.
IH (holding current)-the maximum working current of self-recovery fuse at 25℃;
IT (trip current)-the inimum current for starting protection of self-recovery fuse at 25℃;
In practice, everyone wants to know if the self-recovery fuse will be protected between IH and IT when the current flows through it. What will be its running time? Usually, in the product specification, only IT(2 times or 3 times running time under IH conditions) is given.
When the current flowing through the self-recovery fuse is less than Ih, the self-recovery fuse is always in a low resistance state, and when the current flowing through the self-recovery fuse is greater than It, the self-recovery fuse is in a high resistance state (i.e., protection state) within a certain time range. As we all know, the working principle of self-recovery fuse follows the relationship of q = 0.24rt. Under the same q value, the current changes according to the square relation, and t is the time required to generate the heat. when the current is larger, the action time (time required for protection) becomes smaller, and t = q/0.24ir ..
