Circuit breakers are energy storage after closing.
After the main contacts are closed, the free release mechanism locks the main contacts in the closed position. The coil of the overcurrent striker and the thermal element of the thermal striker are connected in series with the main circuit, and the coil of the undervoltage striker is connected in parallel with the power supply. When the circuit is short-circuited or severely overloaded, the armature of the overcurrent striker suctions, causing the free release mechanism to operate and the main contact to disconnect the main circuit.
When the circuit is overloaded, the thermal element of the thermal striker heats up to bend on the bimetal, pushing the free release mechanism to act. When the circuit undervoltage, undervoltage detent armature release. Also make the free release mechanism action.
Shared excitation detent is used as a remote control, in normal operation, its coil is de-energized, in the need for distance control, press the start button, make the coil energized.
Low-voltage circuit breakers have a variety of protection functions (overload, short-circuit, under-voltage protection, etc.), adjustable action value, high breaking capacity, easy to operate, safety and other advantages, so they are widely used. Structure and working principle of low-voltage circuit breaker by the operating mechanism, contacts, protection devices (various off-trigger), arc extinguishing system and other components.
Expanded Information
Generally speaking, the circuit breaker with three protection functions of overload long delay, short circuit short delay and short circuit instantaneous can realize selective protection, and most of the main lines (including the outgoing end of the transformer) adopt it as the main protection switch.
No short-circuit short-delay circuit-breakers (only overload long-delay and short-circuit instantaneous two-part protection), can not be selective protection, they can only be used in the branch circuit, IEC92 "Marine Electricity" pointed out that: with three-part protection circuit-breakers, in favor of its operational short-circuit breaking capacity value, and used in the branch line of the circuit-breaker, should ensure that it has a sufficient value of the limit of the short-circuit breaking capacity.
No matter which kind of circuit breaker, although all have Icu and Ics these two important technical indicators. However, as a circuit breaker used on the branch line, it can just meet the rated ultimate short-circuit breaking capacity.
The more common bias is rather take the big, not take the right fit, that take the big insurance. But get too big, will cause unnecessary waste (the same type of circuit breaker, its H-type - high breaking type, than the S-type - ordinary type of price is 1.3 times to 1.8 times more expensive). Therefore, there is no need for the circuit breaker on the branch line to pursue its operational short-circuit breaking capacity index.
And for the main line on the use of circuit breakers, not only to meet the requirements of the rated limit of short-circuit breaking capacity, but also should meet the requirements of the rated operating short-circuit breaking capacity, if only to the rated limit of short-circuit breaking capacity Icu to measure the breaking capacity of qualified or not, it will bring the user unsafe hidden danger.
Baidu Encyclopedia - Circuit Breakers