Miniature Circuit Breaker and Earth Leakage Circuit Breaker

Miniature circuit breaker referred to as MCB in the electrical industry, is suitable for overload and short circuit protection of AC 50/60Hz rated voltage 230/400V, rated current to 63A , Can also be used for infrequent operation conversion of the line under normal circumstances.

Residual current protection circuit breaker:

Residual current protection device (RCD for short in the electrical industry), also known as "leakage switch", is a kind of detection of the phase-to-ground leakage or electric shock current that occurs in the protected power grid, as an action trip signal, and completes Protective electrical appliances for action tripping tasks. In a low-voltage power grid equipped with a leakage protector, under normal circumstances, the phase-to-earth leakage current of the grid (unbalanced leakage current for a three-phase grid) is small and cannot reach the operating current value of the leakage protector, so The leakage protector does not operate.

When a fault such as leakage or personal electric shock occurs in the protected power grid, when the current through the leakage or electric shock action current value of the leakage protector detection element reaches its leakage or electric shock action current value, the earth leakage protector will generate an action trip command to make the master controlled The circuit switch action trips and cuts off the power supply, thus completing the task of leakage or electric shock protection. RCD has overload and short-circuit protection functions, which can be used to protect the circuit or motor from overload and short-circuit, and it can also be used for infrequent conversion and startup of the circuit under normal conditions.

What are the similarities and differences between miniature circuit breakers and residual current protection circuit breakers (leakage switches)?

Both play the role of line overload protection. The miniature circuit breaker is the on-off switch that controls the electrical circuit. If air is used as the arc extinguishing medium, it is called an air switch. Generally, it is selected by the rated current (load) and used as the main switch of the electrical circuit. The leakage switch integrates overload, short circuit and leakage protection, and can be installed independently, which is equivalent to a leakage protector plus a miniature circuit breaker or a leakage accessory plus a miniature circuit breaker.

It can be simply understood as when a miniature circuit breaker has a leakage protection function, it is called a leakage protection switch. If it is an electrical device used solely for leakage protection, it is called a leakage protector.

What is the difference between the tripping characteristics of miniature circuit breakers B, C and D? How to apply?

The instantaneous tripping current of class B is 3-5In (rated current), suitable for resistive loads; the instantaneous tripping current of class C is 5-10In, suitable for general loads; the instantaneous tripping current of class D is 10-20In , Suitable for large inductive loads.

The miniature circuit breaker can't close the handle, why?

First check whether there is a short circuit or overload in the output circuit of the miniature circuit breaker. If yes, it is enough to eliminate the fault; if not, replace the miniature circuit breaker.

What is the difference between "1P+N" miniature circuit breaker and "2P" miniature circuit breaker?

The rated voltage of the "1P+N" miniature circuit breaker is 230V AC, which can only break single-phase circuits, and the phase line and the neutral line cannot be connected wrongly; the rated voltage of the "2P" miniature circuit breaker is 400V AC, which can break double Phase/single phase circuit.

What are the main technical parameters of the leakage protector?

The main operating performance parameters are: rated leakage operating current, rated leakage operating time, and rated leakage non-operating current. Other parameters include: power frequency, rated voltage, rated current, etc.

①Rated leakage operating current The current value at which the leakage protector operates under specified conditions. For example, a 30mA protector, when the current value reaches 30mA, the protector will act to disconnect the power supply.

②Rated leakage operation time refers to the time from the sudden application of rated leakage operation current until the protection circuit is cut off. For example, for a 30mA×0.1s protector, the time from the current value reaching 30mA to the separation of the main contact does not exceed 0.1s.

③Rated non-operating leakage current Under specified conditions, the current value at which the leakage protector does not operate should generally be one-half of the leakage operating current value. For example, a leakage protector with a leakage action current of 30mA, when the current value reaches 15mA or less, the protector should not operate. Otherwise, it may malfunction due to too high sensitivity and affect the normal operation of electrical equipment.

④Other parameters such as: power frequency, rated voltage, rated current, etc., when selecting a leakage protector, it should be compatible with the line and electrical equipment used. The working voltage of the leakage protector should adapt to the rated voltage of the normal fluctuation range of the power grid. If the fluctuation is too large, it will affect the normal operation of the protector, especially for electronic products. When the power supply voltage is lower than the rated working voltage of the protector, it will refuse to operate. The rated working current of the leakage protector should also be consistent with the actual current in the loop. If the actual working current is greater than the rated current of the protector, it will cause overload and cause the protector to malfunction.

How to use the leakage protector?

After installing the wiring, press the leakage test button of the leakage protector to create a short-term artificial leakage condition to check whether the leakage protector can operate. The test button should be tested once a month to check the function of the leakage protector. In the case of ground leakage, the leakage protector will automatically trip. Before the fault has been cleared, even if the handle is pushed to the "ON" position, the circuit cannot be reconnected, which avoids artificially connecting the faulty circuit.

How to use leakage accessories?

Used in conjunction with a miniature circuit breaker for overload, short circuit and leakage protection. After installing the wiring, press the leakage test button of the leakage accessory to create a short artificial leakage condition to check whether the leakage accessory can operate. The test button should be tested once a month to check the function of the leakage accessories. In the event of overload or short circuit, the handle of the miniature circuit breaker will act, but the handle of the leakage accessory will not act. When a leakage trigger occurs, both handles move. When resetting, you must reset the leakage accessory handle first. Before the cause of leakage is eliminated, the handle of the miniature circuit breaker and the handle of the leakage accessory cannot be reset.

What are the similarities and differences between leakage switches and leakage accessories?

Both play the role of leakage protection. But the leakage switch can be installed independently, and the leakage accessories must be used in conjunction with the miniature circuit breaker.

Why is it necessary to install a leakage protector after the protection is connected to zero (grounding)?

Regardless of whether the protection is connected to zero or grounding, the protection range is always limited. For example, "protection connection to zero" is to connect the metal shell of electrical equipment with the neutral line of the power grid, and install a fuse on the power supply side. When the electrical equipment encounters a shell failure (a certain phase touches the shell), a single-phase short circuit of the relatively neutral line is formed. Due to the large short-circuit current, the fuse is quickly blown and the power supply is disconnected for protection.

Its working principle is to change the "shell-touch fault" to "single-phase short-circuit fault", so as to obtain large short-circuit current cut-off insurance. However, electrical shell collision faults on the construction site are not frequent. Leakage faults often occur, such as leakage caused by equipment damp, excessive load, excessively long lines, and aging insulation. These leakage currents are small and cannot be quickly cut off. Therefore, the fault will not be automatically eliminated and will exist for a long time. But this kind of leakage current poses a serious threat to personal safety. Therefore, it is necessary to install a more sensitive leakage protector for supplementary protection.

What is the safety of the leakage switch "30mA?s"?

The human body’s perceptual current ---- 1.1mA for males and 0.7mA for females; 16mA for males and 10.5mA for females; children are smaller than adults; the current that is life-threatening in a relatively short period of time is the causing current, from two Understanding from the aspect ---- First, the current reaching 50mA will cause ventricular fibrillation, which is life-threatening, while the current above 100mA will cause death in the center, and there will be no life-threatening below 30mA.

0.1 second: The human heart has a 0.1 second interval for every contraction and expansion. During this 0.1 second, the heart is most sensitive to current. If the current passes through the heart at this moment, even if the current is small, it will cause the heart to tremble and cause Danger.