How To Choose A, B, C, And D Types of Miniature Circuit Breakers?(1)
1. Selection of A, B, C, and D types of miniature circuit breakers
There are four general tripping characteristics of circuit breakers: A, B, C, and D. So how do we choose?
1) A-type circuit breaker: 2 times the rated current, rarely used, generally used for semiconductor protection (generally, fuses are used).
The so-called multiple currents are the anti-impulse current. The switch will not trip for a certain duration. Its characteristic is to avoid the inrush current.
Selection of the release of low-voltage circuit breakers:
The types of release of circuit breakers include overcurrent release, under-voltage release, shunt release, etc.
Overcurrent release can also be divided into overload release and short-circuit current release, and there is a long delay, short delay, and instantaneous points, overcurrent release is the most commonly used.
The setting value of the operating current of the overcurrent release can be fixed or adjustable, and it is usually adjusted by rotating or adjusting the lever. The electromagnetic overcurrent release also has two kinds fixed and adjustable. The electronic overcurrent release is generally adjustable.
The breaking capacity of the circuit breaker refers to the ability to withstand the maximum short-circuit current, so the breaking capacity of the rotating circuit breaker must be greater than the short-circuit current of its protective equipment.
According to the installation method, the overcurrent release can be divided into fixed installation or module installation. Fixed installation is that the release and circuit breaker are processed into one body at the factory, and the rated current of the release is not adjustable once it leaves the factory. The modular installation release, as an installation module of the circuit breaker, can be adjusted at any time and has strong flexibility.
Instantaneous type: 0.02S, for short circuit protection.
Short delay type: 0.1-0.4S, used for short circuit and overload protection.
Long delay type: less than 10S, used for overload protection.
At present, the commonly used DZ series air switches (miniature circuit breakers with leakage protection), the common specifications are: C16, C25, C32, C40, C60, C80, C100, etc., where C represents the tripping current characteristic is C, that is, the tripping current. For example, C20 means that the starting current is 20A, and the tripping characteristic is the C curve. Generally, the circuit breaker of C20 should be selected for the installation of a 3500W water heater, and the circuit breaker of C32 should be used for the installation of a 6500W water heater.
Circuit breakers are used to protect wires and prevent fires, so they should be selected according to the size of the wire rather than the electrical power.
If the circuit breaker is too large, it will not protect the wire. When the wire is overloaded, the circuit breaker will not trip, which will bring hidden dangers to the safety of the family.
2) Type B circuit breaker: 2-3 times the rated current, generally used for pure resistive loads and low-voltage lighting circuits. It is often used in the distribution box of households to protect household appliances and personal safety and is currently used less.
3) C-type circuit breaker: 5-10 times the rated current, it needs to trip within 0.1 seconds. Circuit breakers with this characteristic are most commonly used to protect distribution lines and lighting lines with high on-current.
4) D-type circuit breaker: 10-20 times the rated current. Mainly in the environment where the instantaneous current of electrical appliances is large. It is also rarely used in general households. It is suitable for systems with high inductive loads and large inrush currents and is often used to protect equipment with high inrush currents.
