1. Firstly, the rated voltage should be selected according to the rated voltage, and the rated voltage should be the same.

2. The rated current of the circuit breaker should be greater than or equal to the rated current of the circuit used.

3. The rated interrupting current of circuit breaker should be greater than or equal to the short circuit current of the circuit used.

4. Choose circuit breakers according to environmental conditions, such as altitude, temperature and humidity.

5. Choose circuit breakers with high quality and cost performance according to the brand.

6. Check the circuit breaker for special interruption.

However, different types of circuit breakers should be selected for different loads. The most common loads are distribution lines, motors and household and similar household (lighting, household appliances, etc.).

Corresponding to this, there are distribution protection type, motor protection type and household and similar household protection type circuit breakers. These three types of circuit breakers have different protection properties and characteristics.

For distribution circuit breakers, they are classified as A and B.

Category A is non-selective and Category B is selective. The so-called selective type refers to the circuit breaker.

General selection principles:

Choose the type and pole number of circuit breaker according to its use.

The rated current of the circuit breaker is selected according to the maximum working current.

Choose the type of release, the type and specification of accessories according to the need.

Specific requirements are:

The rated operating voltage of circuit breaker is greater than or equal to the rated line voltage.

(2) The rated short-circuit breaking capacity of circuit breakers is greater than or equal to the calculated load current of the circuit.

(3) The rated short-circuit breaking capacity of circuit breakers is greater than the maximum short-circuit current that may occur in the circuit (generally calculated according to the RMS).

(4) The single relative ground short circuit current at the end of the line is more than 1.25 times the instantaneous (or short delay) tripping setting current of the circuit breaker.

The rated voltage of undervoltage tripper of circuit breaker is equal to the rated voltage of line.

The rated voltage of the shunt tripper of the circuit breaker is equal to the voltage of the control power supply.