When selecting a miniature circuit breaker, the following conditions should be considered:
1) The rated voltage of the circuit breaker shall not be less than the rated voltage of the line;
2) The rated current of the circuit breaker and the current rating of the overcurrent release shall not be less than the calculated current of the line;
3) The rated short-circuit breaking capacity of the circuit breaker is not less than the maximum short-circuit current in the circuit;
4) Selective distribution circuit breakers need to consider the short-delayed short-circuit breaking capacity and delay protection level coordination;
5) The rated voltage of circuit breaker undervoltage release is equal to the rated voltage of the circuit;
6) When used for motor protection, the selection of the circuit breaker must take into account the starting current of the motor and make it inactive during the starting time; design calculations refer to "Industrial and Civil Distribution Design Manual";
7) Select circuit breakers should also consider the selective cooperation of circuit breakers and circuit breakers, circuit breakers and fuses.
Circuit Breaker: A mechanical switching device that can turn on, load, and break the current under normal circuit conditions, and can also be turned on, carry a certain amount of time, and cut off current under specified abnormal circuit conditions.
Miniature circuit breaker working principle
Miniature circuit breakers consist of operating mechanisms, contacts, protection devices (various trip units), and arc extinguishing systems. Its main contacts are either manually operated or electrically closed. After the main contact is closed, the free tripping mechanism locks the main contact in the closing position. The coil of the overcurrent release and the thermal element of the thermal release are connected in series with the main circuit, and the coil of the undervoltage release is connected in parallel with the supply. When the circuit is short-circuited or severely overloaded, the armature of the over-current release pulls in, causing the free tripping mechanism to act, and the main contact opens the main circuit. When the circuit is overloaded, the thermal element of the thermal release heats up to bend the bimetal and push the free tripping mechanism. When the circuit is under voltage, the armature of the undervoltage release releases. The free trip mechanism is also actuated.

Including rccb

There are three reasons why a Miniature Circuit breaker trips at home. The first is overload, the second is short circuit, and the third is leakage.

The first is that overloading means that too many high-power electrical appliances are used at the same time to exceed the rated current of the Miniature Circuit breaker. It is estimated that you will not calculate, and then you should try to open a few more.

Second, the short circuit may be a short circuit of an electrical appliance, it may also be a short circuit of the dark appliance wire, without any electrical equipment to try if you also jump to consider the circuit is short circuit, of course, if it is a switch with leakage protection, there may be leakage of electricity .

The third kind, if it is a switch with leakage protection, the line or appliance will trip with a little leakage, generally 30mA.

If this is the first case, you should open a little less electrical equipment. A larger circuit breaker can also be used, provided that your line cannot be too thin and it should be larger than the rated capacity of the circuit breaker.

If it is the second case, there is a short circuit inside an appliance. It is OK to repair this appliance. If you are short-circuited, you must ask the professional to check it out.

If it is the third case, an electrical leakage, then one by one plugged in to go to the power to try one by one, to jump that is the problem of which electrical appliances, if it is a hidden line leakage, non-professionals can not find out For a switch that does not have leakage protection, it is only one less safety protection.

Note: The switch with leakage protection is one block larger than the ordinary switch. It should be wider. There is a small button on the switch with leakage protection. Observe yourself to distinguish which one you belong to.

Residual current protection device RCD Residual current devices


Its core wraps around all current-carrying conductors of an electrical circuit. The magnetic flux generated in the core is related to the arithmetic sum of these conductor currents in a moment; the current flowing in one direction is assumed to be positive (I1), The current flowing in the opposite direction is negative (I2).

In the normal loop without fault, I1 + I2 = 0, there is no magnetic flux in the core, and the electromotive force in the coil is zero. The ground fault current Id flows through the core to the point of failure but returns to the power via the earth or via the protection line of the TN system.

The current through the conductors of the magnetic core is therefore no longer balanced and the current difference creates magnetic flux in the magnetic core.

This current is called the "residual" current and this principle is also considered as the "residual current" principle.

The varying magnetic flux generated in the magnetic core induces an electromotive force in the winding, so that the current I3 flows through the coil that operates the trip unit. If the residual current is greater than the value of the current that can cause the trip unit to act, whether it is direct action or via the electronic, relay action, the circuit breaker will have to trip.