How to choose circuit breakers

Update date:2018-02-28 Source:MAXGE

How to choose circuit breakers

   The basic principle of the circuit breaker is that when the normal operating current flows through the circuit breaker, as time goes by, the calorific value detected by the protective measurement and control device in the circuit breaker is not large and does not exceed the heat generation threshold limit value, and the circuit breaker of course does not The circuit breaker performs the tripping operation; when the non-normal large current flows through the circuit breaker, the protection and control device in the circuit breaker detects the larger heating value and crosses the calorific value threshold, and the circuit breaker performs the tripping operation.

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   Circuit breaker options mainly look at the following aspects

     1. Rated voltage, that is, the molded case circuit breaker where the distribution system voltage level is, the common low-voltage power distribution system is 400V, as we ordinary people living in the district, power distribution room distribution transformer ratio is 10 / 0.4kV, the general use of TN-CS or TN-S system, the transformer neutral ground directly; of course, does not rule out 690V, such as wind farm low voltage distribution is generally 690V. So the rated voltage of the molded case circuit breaker Adapt to the system voltage, the limit breaking capacity and breaking capacity of molded case circuit breakers are closely related to the rated voltage.

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     2. Rated ultimate short-circuit breaking current Icu, according to GB14048.2 low-voltage circuit breaker standard, refers to the circuit breaker breaking a short-circuit current does not require it to carry the rated current breaking capacity; rated short-circuit breaking current Ics, is broken circuit breaker After a short circuit current also need to continue to carry the rated current breaking capacity, which is generally 25,50,75,100 percent of the former.

     3. The rated current of the circuit-breaker, the rated current of the circuit-breaker, is equal to the rated uninterruptible current Iu and is equal to the free-air heating current Ith, which means that the circuit-breaker can carry continuously without exceeding the temperature rise current. Circuit breaker circuit breaker current refers to the circuit breaker can hold the maximum overcurrent release rated current,


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