An essential tool in the electrical system that helps to guard the line from defects including short circuit and overload is the molded case circuit breaker The safe and steady running of the electrical system depend on the proper choice of molded case circuit breakers. To guarantee that the chosen molded case circuit breaker can satisfy real needs and has the traits of dependability, stability and economy, it is advisable to thoroughly analyze elements including technical parameters, type, brand and quality, and accessory selection. Some ideas are readily confused with one another since users do not have a thorough knowledge of the features and technical requirements of molded case circuit breakers; so, some deviations and misunderstandings usually arise in actual implementations. This article offers a thorough introduction to the crucial factors consumers should be aware of when choosing and operating molded case circuit breakers so as to enable users fairly decide to use molded case circuit breakers.
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01 Classification and function of circuit breakers
Based on their construction, circuit breakers fall into both plastic shell and universal type. Among them, molded case circuit breakers fit as protective equipment for transformers, motors, capacitors, etc. or as distribution system rated voltage of 690V, frequency of 50/60Hz, and rated current of 16 to 1600A. It mostly distributes electric energy and shields every branch and electrical equipment from undervoltage, short circuit, overload, and leakage. It can also be applied for occasional conversion of electrical equipment and lines. It is extensively applied in industry, agriculture, transportation, mining, civil construction and national defense; it also greatly helps to transmit and distribute electricity, control and protection of circuits. This is a rather widely used and broadly used product.
02 Selection principles of molded case circuit breakers
Common electrical protection device utilized extensively in many different electrical systems are molded case circuit breakers. One should take into account the following ideas while choosing:
The rated voltage and rated current of the electrical system will help one choose an appropriate molded case circuit breaker. To guarantee that the circuit breaker can operate as intended, its rated current should, all things considered, be somewhat more than that of the electrical system. At the same time, the rated voltage of the circuit breaker should also conform to the rated voltage of the electrical system to ensure that it can withstand voltage fluctuations and overvoltages in the system.
One should give the circuit breaker’s short-circuit capacity some thought. In the case of a short circuit, short-circuit capacity is the highest current the circuit breaker can handle. To guarantee that it can withstand the short-circuit current in the electrical system and prevent equipment damage and personal injury caused by short circuits, one must choose an appropriate circuit breaker depending on the short-circuit current of the electrical system.
One has to take into account the circuit breaker’s short-circuit capacity. In the case of a short circuit, short-circuit capacity is the highest current the circuit breaker can handle. Selecting a proper circuit breaker depends on the short-circuit current of the electrical system to guarantee that it can withstand the short-circuit current in the system and prevent equipment damage and personal injury resulting from short circuits.
Third, the rated operating current and rated number of operations of the circuit breaker need to be considered. The rated operating current is the maximum current the circuit breaker can generally switch; the rated number of operations is the maximum number of times the circuit breaker can normally switch. To guarantee that the electrical system can operate normally and have a sufficient life, one must choose an appropriate circuit breaker depending on the load conditions and frequency of use.
The environmental conditions and installation methods of the circuit breaker need to be considered. The circuit breaker’s environmental surroundings cover elements including temperature, humidity, and corrosion. One should choose an appropriate circuit breaker based on the real circumstances. Simultaneously, one must also take into account the circuit breaker’s installation technique—that of fastening, wiring, etc.—to guarantee that it may operate consistently and safely.
Choosing an appropriate molded case circuit breaker calls for weighing several elements, including the rated voltage and rated current of the electrical system, short-circuit capacity, rated operating current and rated number of operations, environmental conditions and installation techniques. The most appropriate circuit breaker can only be chosen by fully analyzing the real circumstances to guarantee the safe and dependable running of the electrical system.
03 Matters needing attention when selecting molded case circuit breakers
The rated current of the circuit breaker frame grade is the rated current of the maximum trip unit that can be fitted in the frame and plastic shell of equal basic dimensions.
The rated current of the circuit breaker is the current the trip unit of the circuit breaker can pass for a lengthy period of time, also referred to as the rated current of the circuit breaker trip unit.
The same series comprises several frame grade rated currents as well as several rated currents in the same frame grade rated current. The DZ20 series contains, for instance, frame ratings of 100, 225, 400, 630, 800, 1250, and 100 frame ratings of 16A, 20A, 25A, 32A, 40A, 50A, 63A, 80A, and 100A; the 225A frame ratings are 100A, 125A, 160A, 180A, 200A, and 225A.
Though the size and breaking capability of the circuit breakers vary, DZ20-100 and DZ20-225 frame ratings have 100A rated currents. Consequently, while choosing, the model should be filled in totally, that is, the rated current of the circuit breaker inside the particular frame rating. The selected rated current classification is based on the (1.25) priority coefficient: on the one hand, it meets and satisfies the needs of the maximum line and electrical component rated current; on the other hand, it is for standardizing to acquire the most correct use of wires and processing advantages.
Therefore, the levels it specifies are: 3 (6), 8, 10, 12.5, 16, 20, 25, 32, 40, 50, 63, 80, 100, 125, 160, 200, 250, 315, 400A, etc. This control means that only the 100A specification can be used when the calculated load is 90A, therefore somewhat influencing the protection performance.
04 Selection of molded case circuit breakers
Demand study indicates that you should consider the following factors in order to choose a fitting molded case circuit breaker:
Choose a reasonable rated current depending on the size of the circuit. Usually, one chooses a circuit breaker somewhat bigger than the circuit current.
To guarantee that the circuit breaker operates within a safe range, choose one based on the voltage level of the circuit such that it has a sufficient maximum voltage.
Choose a circuit breaker with plenty of opening and closing times to guarantee its service lifetime.
Operating mechanism: Select a circuit breaker with a simple and stable operating mechanism to facilitate maintenance and replacement.
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When choosing a molded case circuit breaker, pay attention to the following points:
1. Choose products produced by regular manufacturers to ensure quality and safety performance.
2. Avoid choosing circuit breakers that are too small or too large to avoid affecting the circuit protection effect or causing waste.
3. Pay attention to the maintenance and replacement costs of the circuit breaker for long-term maintenance and care.
4. During installation and use, strictly abide by relevant regulations and operating procedures to ensure safety and reliability.
Post time: 7 月-18-2024