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Differences and applications of miniature circuit breakers

Author: Site Editor     Publish Time: 2023-03-07      Origin: Site

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Differences and applications of miniature circuit breakers

For miniature circuit breakers, 1pn, 1p and 2p are usually used for switch control of single-phase electrical equipment;



In order to reduce costs, 1p can be used, but advanced circuit breakers must have leakage tripping functions. In order to prevent accidents caused by the confusion of the live line and the neutral line during the maintenance process, the superior power supply must be cut off;

To avoid this problem during overhaul, 1pn can be used;

In the case of the same 18mm modular circuit breaker, there are differences between 1p and 1pn installed inside. In the short-circuit accident state, the former must have a higher "ultimate breaking capacity" than the latter. After all, space is an important factor affecting breaking capacity.

Therefore, for more critical, more frequent maintenance and operations, and for power circuits prone to failure, 2p is better (higher cost).

When using 1p, the lighting distribution box must have a leakage trip function, and at least the incoming line (or the upper layer of the outgoing line) should use a leakage circuit breaker.

It is perfectly fine to use 1P+N for ordinary socket circuits, but it will not work if you want to add leakage, because 1P+N circuit breakers cannot be assembled with leakage protection accessories and other electrical accessories.

Three-phase circuit breakers are generally divided into three types, namely 3P, 3PN and 4P


3P: Pure three-phase electrical equipment only uses three wirings. In the case of no single-phase load, it will trip when a short circuit occurs to ground or between phases. Otherwise, when one-phase N-wire loads, the N-wire circuit breaker will act as a leakage current;

3PN: After the four-wire l1l2l3n passes through the transformer coil, three-phase power or single-phase power can be used. Regardless of whether the three-phase load is balanced or not, the leakage switch does not operate; it only operates when there is leakage, that is, single-phase grounding or phase-to-phase short circuit;

4P: The use of four-wire L12L3 passing through the transformer coil is the same as that of 3PN, the difference is that 4P breaks the N wire, and 3P keeps the N wire.


Four-pole circuit breakers are divided into four types: A, B, C and D:

A: The N poles are not equipped with an overcurrent release, and the N poles are always connected together, and are not closed or disconnected from the other three poles.

B: There is no overcurrent release for the N pole, and the N pole is connected and opened with the other 3 poles.

C: The N pole is equipped with an over-current release, and the N pole is connected to the other 3 poles.

D: The N pole is equipped with an overcurrent release device, and the N pole is always connected, not closed or disconnected from the other three poles.


In the case of using four poles, it is necessary to point out which product to choose, because it is the same as four poles, but whether to install an overcurrent release device on the n line has different functions and uses.

The overcurrent release is installed on the n-wire, which can be used in three-phase four-wire distribution lines with single-phase load as the main component, and can also be used in non-linear loads that generate a large number of harmonics, such as gas discharge lamps, thyristor dimming , speed control lines and other occasions with special requirements. In general, an n-wire circuit breaker without an overcurrent release can be selected for the equipment circuit.

In fact, although A and D are called four-pole circuit breakers, their N poles are always connected and will not be closed or disconnected with the other three poles. Therefore, this commonly known as "false four-pole" molded case circuit breaker is 3PN, which is not essentially different from a three-pole molded case circuit breaker. The only thing more useful than a 3-pole molded case circuit breaker is that wiring access may be easier in a packaged cabinet. Therefore, this circuit breaker can only be used for three-phase loads, and only a small number of single-phase loads (if there is a control power supply, use a complete 220V system).

If the A, B, C, and D types of circuit breakers are selected incorrectly, not only will they fail to protect, but will cause major problems. This is the most confusing problem in design and use at present, and it should be paid attention to.

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