Molded Case Circuit Breaker is widely used in industry, agriculture, transportation, mining, civil construction and national defense departments. It plays a great role in power transmission and distribution, circuit control and protection. It is a product with large usage and wide range. Some concepts are easy to confuse with each other because users do not have a deep or comprehensive understanding of the characteristics and technical requirements of Molded Case Circuit Breakers, and some errors and misunderstandings often occur in practical applications. In order to help users choose and use Molded Case Circuit Breakers reasonably, Kechuang Online introduced the problems that users often encountered when choosing and using Molded Case Circuit Breakers.
Circuit Breaker Shell Grade
The rated current of circuit breaker housing grade refers to the rated current of the maximum tripper that can be installed in the frame and plastic shell of the same basic size.
The rated current of circuit breaker refers to the current that the tripper in the circuit breaker can pass for a long time, also known as the rated current of the circuit breaker tripper.
In the same series, there are many kinds of rated current of shelf grade, and in the same shelf grade, there are many kinds of rated current. The volume, shape and breaking capacity of circuit breakers are different, so when choosing the circuit breaker, it is necessary to fill in the model completely, that is, the rated current of the circuit breaker within the rated current of the specific shelf grade. Rated current classification is based on (1.25) priority coefficient: on the one hand, it meets and meets the needs of the maximum rated current of lines and electrical components; on the other hand, it is for standardization, in order to achieve the best use of wires and processing benefits. Therefore, the levels specified are: 3 (6), 8, 10, 12.5, 16, 20, 25, 32, 40, 50, 63, 80, 100, 125, 160, 200, 250, 315, 400 A, 500 A, 630 A, 800 A, 1000 A, 1250 A, 1600 A, etc. Because of this regulation, when the line calculates the load of 90A, only 100A specification can be selected, so its protection performance will be affected to a certain extent.
The current setting value of the tripper means that the tripper is adjusted to the action current value. It refers to the multiple of the rated current in, which is the action current value. For example, when the overcurrent is set to 1.2, 1.3, 5, 10 times the current, it is written as Ir = 1.2In, 1.3In, 5In, 10In, etc. Nowadays, the rated current of some electronic trippers with long overload and delay is adjustable. The adjusted current is actually the rated current and the maximum current that can be passed for a long time.
The rated working current is the actual working current of the contacts when the circuit breaker is equipped with auxiliary contacts (accessories) under a certain working voltage. The current is 3A or 6A, which is used to control and protect the circuit.
Rated insulation voltage
The rated insulation voltage is the voltage value of the designed circuit breaker, and the electrical clearance and creepage distance should be determined by reference to this value. Some circuit breakers do not specify rated insulation voltage. The maximum rated working voltage should be regarded as rated insulation voltage. In any case, the maximum rated working voltage should not exceed rated insulation voltage.
The rated working voltage refers to the on-off capacity and the voltage value related to the use category. The rated working voltage of the Molded Case Circuit Breaker is mostly 50Hz and 380V, but there are also 50Hz and 600V, 380V and 50Hz rated working voltage of the Molded Case Circuit Breaker. It is absolutely not allowed to use 660V or 1140V power supply voltage.
The rated control power supply voltage is the voltage when Molded Case Circuit Breaker is equipped with shunt tripper and motor mechanism accessories. There are two kinds of voltages: AC and DC. When selecting, AC or DC must be indicated.
Rated limit short circuit sectional capacity
The rated limit short circuit breaking capacity refers to the breaking capacity under specified conditions. After operating according to the prescribed test procedure, the rated current of the circuit breaker is not considered to continue to be loaded.
The rated short-circuit breaking capacity refers to the breaking capacity under specified conditions. After following the prescribed test procedure, it is necessary to consider that the circuit breaker continues to carry its rated current.
In order to meet the needs of different users, many circuit breaker manufacturers in China now divide the short-circuit breaking capacity of rated current of the same shelf into different levels. When users select, they should meet the limit short-circuit breaking capacity of the circuit breaker, and the expected short-circuit current of the circuit can meet the requirements without adding the insurance system artificially. Number to avoid waste.
The rated short-circuit breaking capacity can be 25%, 50%, 75% and 100% of the rated limit short-circuit breaking capacity. Most of the circuit breakers are 50%-75%, and very few are 100%(Ics=Icu).