How to choose circuit breaker (air switch) type C and type D?

How to choose the type C and D of the circuit breaker (air switch)?

There is usually a distribution box somewhere in our home, and a corresponding switch will be installed in the distribution box. There are mainly two kinds of switches installed in the distribution box: the first is the ordinary air switch and the second is the leakage protection switch.But these switches are divided into different types, how on earth do we choose? For example, now someone asks such a question: how to choose the C type and D type of the air switch?

1、What is the air switch?

Air switch is a kind of switch which uses air as arc extinguishing medium and then extinguishes arc through arc extinguishing grid.Because the electric circuit will produce an arc when it is disconnected in an instant, the arc is very dangerous, so the arc must be extinguished.The air switch uses air to extinguish the arc.

The air switch can be used as the main switch to turn on and off the circuit, so as to realize the function of turning on and off the circuit.In addition, it can also achieve the role of the distribution of our indoor circuits. The air switch also has three kinds of protection functions, namely, short-circuit protection, overload protection and under-voltage protection.

2、What are the type C and type D of the air switch?

The air switch uses the internal component tripping to achieve its due function, and the internal tripping curve is divided into different types according to different types.According to the tripping curve, the air switch can be divided into A type curve, B type curve, C type curve and D type curve. In fact, it is divided according to the sensitivity of tripping.

Reference Table for Household Selection

Wiring precautions: determine the thickness of the wire according to the current.

C-type tripping curves are common in some inductive loads and lighting circuits.In other words, the C-type curve is generally used in the household lighting distribution box, and the deconstruction interval of C-type curve is 5-10In.

D-type curve is common in some high inductive load circuits and high impact circuit circuits. The drop of this kind of circuit corresponds to the power circuit. In other words, some power distribution boxes in the basements use D-type curves. The tripping interval of D-curve is 10-14ln.

3、How to choose a household air switch

First, we need to know that household air switches belong to the C-shaped curve. So for the home air switch, we choose the C curve air switch. The air switch of C curve is our common C10A, C16A, C20A, C25A, C32A, C40A, C50A and other different models, in which the number represents the rated current, and the letter C represents the type of tripping curve.

Second, we need to know that the rated current of the air switch must be selected according to the calculated current of the load circuit of the air switch. For example, if the calculated current in the circuit is 10A, then we choose it according to 10 times 1.2, which is 12A. What is greater than 12A is the air switch of 16A, so we should choose the air switch of C16A.

4、How to configure switches for home use

The first point is the choice of master switch for home use. It is recommended that you choose the air switch of 2P. The rated current of the air switch is selected according to the calculated current when all the appliances in our home work at the same time. The common models of the master switch are C32A, C40A, C50A, and so on.

The second point is the switch selection of the shunt circuit in the home distribution box. It is recommended that you choose 2P or 1P+N leakage protection switch. The rated current of the leakage protection switch is selected according to the working current of all electrical appliances in this circuit. The common socket circuit is 16A, and the kitchen and bathroom can choose 20A or 25A. In addition, the leakage current is 30 Ma.

Basic principles for selection of air switches

Air switch rated working voltage ≥ line rated voltage, air switch rated working current ≥ calculated load current, and because air switch has overload and short-circuit protection function, so take into account the setting current of the thermal release (equal to the rated current of the control load) and the instantaneous setting current of the electromagnetic release (greater than the peak current of the normal working time of the load current).

Sometimes, the C type air switch selected according to the calculated load current will be tripped immediately, while the D type air switch with the same rated working current will not be tripped immediately, which is related to the tripping characteristic of the air switch. In a simple way, it is the ability to withstand the starting impulse current. Type C air switch k is 5-10 times, type D air switch K is 10-20 times, k is the ratio of working current to rated current of air switch.

Thus it can be seen that the ability of D-type air switch to withstand impulse current is stronger than that of C-type air switch, so it is suitable for loads with large impulse current. Therefore, although the selection of the rated current of the air switch is reasonable, because the load used has a large impulse current when starting, for the C-type air switch, it is to start the impulse current transition and lead to tripping and can not be closed. With D-type air switch, there will be no failure to close.

Although the air switch selected according to the current calculation of the line load may be tripped immediately and cut off the power supply by type C, the higher rated current of the switch can solve the phenomenon of immediate tripping, but the price is higher than that of type D air switch with the same rated current. Although the reliability of power supply has been improved, the economy and safety of power consumption have been reduced.

With regard to how to select type C and type D in air switches, JONCHN Electric analyzes the meaning of type C and D of air switches, and finally introduces the specific suggestions for the selection of household switches in detail, and give you a detailed analysis of the selection of various switches in the indoor distribution box.