A current-limiting circuit breaker is a type of circuit breaker with a short breaking time, sufficient to break the circuit before the peak current of the short circuit occurs. According to the current-limiting principle, this type of circuit breaker can be classified into the following four types.
The current-limiting circuit breaker is composed of a current-limiting fuse and a DC circuit breaker.
② The current-limiting circuit breaker composed of self-resetting fuses and DC circuit breakers. Its principle is to utilize the high resistance, high voltage, and high temperature plasma gas in the self-resetting fuse to limit the increase of short-circuit current. The current-limiting effect is strong, and it can significantly enhance the breaking capacity of small-capacity circuit breakers.
③ The current-limiting circuit breaker is composed of a current-limiting wire and an ordinary circuit breaker. The current-limiting wire is a kind of iron-based alloy with a high resistance coefficient, which can limit the increase of short-circuit current in the line.
④ The electrically operated expulsion circuit breaker is also a commonly used type of flow-limiting circuit breaker. It utilizes the power generated by the short-circuit current passing through the contact circuit to quickly repel the contacts, thereby cutting off the faulty circuit before the short-circuit current reaches its peak.
The DWX15 series, DZX10 series, and DZX19 series plastic encased circuit breakers are commonly used in China for current limiting. Additionally, the 3VE series and C45 series products imported from abroad also have current limiting functions.
Structure and working principle.
The structure of the current-limiting circuit breaker is basically the same as that of a regular circuit breaker. The main difference lies in the elongation of the contact circuit size and the lengthening of the parallel conductors, as well as the ability of the static contacts to move backward. The structure is shown in Figure 1. When a short-circuit current passes through, the huge electrostatic repulsion force between the parallel conductors of the static contact circuit overcomes the effect of the spring structure and working principle, forcing the static contact bracket to move backward. Before the action of the locking mechanism, the static contacts quickly repel each other, generating an arc in advance, which accelerates the locking action and introduces an arc resistance for current limiting earlier, strengthening the arc-extinguishing function of the arc extinguishing chamber, and enabling the circuit to break quickly. Since the short-circuit current does not reach a large value during this period, the current-limiting effect is achieved.
