The difference between molded case circuit breaker and air switch, how to choose the appropriate air switch?

Low-voltage circuit breaker can be divided into "low-pressure molded case circuit breaker" and "low-voltage frame circuit breaker", the former for low-voltage small current, the latter for low-voltage large current, the low-pressure molded case circuit breaker commonly known as "automatic air switch".

The main difference between air opening and plastic case:

1, molded case circuit breaker is also "air circuit breaker". Commonly used air circuit breakers are frame circuit breakers and molded case circuit breakers. The former has large capacity, large rated breaking current and large volume, so there is no plastic case, and the parts of the breaker are mounted on a steel frame. The latter is relatively small capacity, rated breaking current is also small, so the volume is small, the whole circuit breaker is protected by a plastic case. General frame circuit breakers are used for power circuits with high current, while molded case circuit breakers are used for load circuits.

2, air switch in small current circuit mainly play the role of "isolation" and "protection device", also called automatic switch, also called air circuit breaker;

3, circuit breaker has a good ability to extinguish arc, in the case of short circuit and large current, automatic trip; In the high voltage, high current circuit, commonly used for power outage, power, switch on, disconnect load operating electrical appliances;

4, current grade: plastic case circuit breaker is generally 630A below, air circuit breaker is generally 630A above, micro circuit breaker is generally 63A below;

5, the difference between the voltage level: the general air switch used voltage level is below 500V, and the circuit breaker can usually be used for more than 220V of the voltage level;

6, the ability of the current is different: the general circuit breaker can withstand the load and short circuit current is larger;

7, the difference between arcing medium and mode: the arcing medium and mode of circuit breaker not only have air circuit breaker, but also vacuum circuit breaker, more oil circuit breaker, less oil circuit breaker, sulfur hexafluoride circuit breaker, etc.;

8, the difference between supporting equipment: generally speaking, the measurement of circuit breaker is relative to the air switch, and the supporting equipment of the logical and executive departments is more complex.

Circuit breaker vacuum circuit breaker and SF6 circuit breaker and other models, its breaking current is larger than the ordinary air switch, the breaking capacity is also larger, vacuum circuit breaker is generally used for 6KV system, SF6 circuit breaker for 500KV substation, both with DC 110V as the control power supply, triggered by the control signal will act, The general air switch used in 380/220 system, equivalent to a knife switch.

Air open option:

1, the first is the main brake: you can use 25-40A, which is calculated according to the maximum power of the family. This power should consider a few electric appliances that add later, if do not consider, the likelihood can exceed set current because of load, frequent trip. Total brake = maximum power /220V.

2. If the maximum power of the family is 8000W, the total brake =8000/220= 36.4A. Commonly used specifications 10, 16, 20, 25, 32, 40, 63A, in the short-circuit or circuit breaker display as C10, C16, C20, C25, C32, C40, C63, you need to choose 40A 2P (bipolar, zero live wire double short) short-circuit as the main brake. All branches have conditions to choose 1P leakage protector, no conditional lighting can choose 1P circuit breaker. Water heater, air conditioner, precision appliances, kitchen appliances, lighting, one way. Hop floor can also be divided by floor partition.

3, lighting generally choose 10A, air conditioning and water heater can use 16-25A according to the power, appropriate amplification point, do not start the moment the current is too large and trip. Precision appliances 20A, kitchen appliances 20-25A.

Note:

1. The rated current of air switch is determined by the calculation current of the line.

2. The short-circuit setting current of the air switch should avoid the normal working starting current of the line.

3. Check the breaking capacity of air switch according to the maximum short-circuit current of the line.

4, according to the minimum short-circuit current of the line to verify the sensitivity of the air switch action, that is, the minimum short-circuit current of the line should not be less than 1.3 times of the air switch short-circuit setting current.

5, according to the short-circuit impact current on the line (i.e. the maximum instantaneous value of short-circuit full current) to check the rated short-circuit connecting capacity of the air switch (maximum expected peak current), that is, the latter should be greater than the former.