Electrical engineers all believe thatModel and specifications of miniature circuit breakersOften very complex, it is not easy to fully understand this product and use it correctly. Today, I am very pleased to be able to interpret these complex specifications with the engineers from Weikewei.

Operating short-circuit breaking capacity Ics - the short-circuit current capacity of an electrical appliance to make and break under specified test procedures and parameters. After testing, it still has a certain dielectric withstand voltage capability, and it is necessary to consider continuing to withstand its rated current. Short time withstand current Icw - the short-term withstand current value that a circuit breaker can withstand without damage under specified test conditions. The short-time withstand current Icw is only applicable to electrical appliances with short-circuit short delay characteristics.When the rated current is below 600A and the short-circuit current is not large, a molded case circuit breaker can be used; When the rated current is high and the short-circuit current is also high, a universal circuit breaker should be selected.The general selection principle is: (1) The rated current of the circuit breaker is ≥ the load working current; (2) The rated voltage of the circuit breaker is greater than or equal to the rated voltage of the power supply and load; (3) The rated current of the circuit breaker release is ≥ the load working current;

(4) The maximum breaking capacity of the circuit breaker is ≥ the maximum short-circuit current of the circuit; (5) Single phase to ground short-circuit current at the end of the line/instantaneous (or short-circuit) setting current of the circuit breaker release ≥ 1.25; (6) The rated voltage of the circuit breaker undervoltage release is equal to the rated voltage of the circuit.

If there are other parameters that exceed the standard, how can we avoid them?

a. Add other protective devices (such as fuses) as backup protection on the power side of the circuit breaker

b. By using a current limiting circuit breaker, the corresponding product can be selected based on the allowable current characteristics or current limiting coefficient (i.e. the ratio of the actual breaking current peak to the expected short circuit current peak) provided by the manufacturer

c. You can choose a circuit breaker with a large capacity. All types of short circuit protection circuit breakers must be able to carry unrestricted short circuit current transient values in the closed position, and must also be able to carry short circuit current within the specific delay range. Circuit breaker product samples, the rated peak with stand current and the rated short-term with stand current (1s current) of the product are generally given When it is an alternating current, the short-time withstand current should be based on the effective value of the periodic component of the unrestricted short-circuit current.

d. The selected circuit breaker for sensitivity coefficient verification should also go under sensitivity coefficient verification based on short circuit current. Sensitivity coefficient coefficients to the ratio of the minimum short circuit current in the circuit (usually taking as the two-phase or single phase short circuit current at the motor terminal or distribution line end) to the immediate or delayed release setting current of the circuit breaker The sensitivity coefficient during two-phase short circuit should not be less than 2, and the sensitivity coefficient during single-phase short circuit can be taken as 1.5 for DZ type circuit breakers and 2 for other types of circuit breakers. If the sensitivity coefficient does not meet the above requirements after verification, in addition to adjusting the set current, a delay release can also be used as a backup protection.

6. The parameter determination of the shunt and undervoltage release should be equal to the rated voltage of the line, and the power source category (AC, DC) should be determined according to the control line situation. The rated control power supply voltage series specified by the national standard are DC (24), (48), 110, 125, 220, and 250V; Communication (24), (36), (48), 110, 127, 220V, the data in parentheses is not recommended.

There will be more professional technical seminars in the future, and we will continue to discuss and exchange ideas with the engineers at Weikewei.