What is the time current characteristics of the machine and why they are important

During normal operation of the network through the circuit breaker current flows. But if the current passing through the machine, will increase the machine is activated by the operation of a thermal trip element.

So, the operating characteristic of the circuit breaker just shows the relationship response time tripping depending on the currents and actually has a very important value.

The complexity of the characteristics lies in the fact that its expression is required the use of graphs. After all, machines with the same nominal value, but different characteristics will be working with different time. And this difference will depend on whether current characteristic used in the product.

This allows the use of AB with an identical nominal value, but different characteristics for a variety of load types.

Indeed, in industry there is often transient increase in current strength (so-called inrush current), which is not emergency mode, which means that the tripping circuit breaker will stop the process, which allow it is impossible.

You've probably seen that on any AB there is a certain character string abbreviation, usually "B", "C", "D", which is precisely characterized by the time current characteristic of the product.

So, it is these letters, and is characterized by the multiplicity of the electromagnetic trip setpoint to nominal machine and another time current characteristic.

Let us now look at what is encrypted in the above representation of the value.

decipher values

To understand, let's consider the following example. Take a pair AB with rated breaking current of 16 amperes, but one of them will be a characteristic of «B», and the other with the «C».

In this range of the electromagnetic trip release for "B16" will be from 3 to 5 rated currents, i.e. from 48 A to 80 A.

A machine for the characteristic of "C16" operating range of the electromagnetic release is from 5 to 10 nominal values, i.e. from 80 A to 160 A.

And it turns out, if we skip through the machines amperage of 90 amps, the circuit breaker with characteristic "B" is practically shut down instantly, but the machine response time with the category "C" will be equal to a few seconds (the time it takes to heat the bimetal Plates).

Almost all private homes and even more so the apartments there is a purely resistive loads and powerful engine includes extremely rare (almost no inrush currents). Therefore, it is preferable to use the circuit breakers with the characteristic "B".

But at the moment the most used machines with characteristic "C", which are the universal solution for both the industry and the private sector.

Category machines with «D» is used only in networks where there is a very powerful engine, and therefore are often quite large inrush currents.

Looking at the above presented graph you can see that the curve is divided into three lines. So the top-most corresponds to the cold of the machine, the lowest "hot" state machine and the average (dotted) line shows the operating characteristic machines denominated 32 Ampere.

You may ask: "What do you mean" cold "and" hot "state?" And this means: it is natural that the newly included machine will have a low temperature of the internal parts, therefore, the current flow need longer reheat bimetallic plate. And it is logical that the automatic shut-off time will be longer.

If we consider the "hot" machine, the passing current will take much less time to heat the wafer, and therefore, the deactivation is performed with less time.

Where will operate the solenoid release, and where the thermal element

Let's take the example of a circuit breaker with a characteristic "C" will understand under what currents thermal element will work, and under what will fire the solenoid trip unit. Take for example the machine on the rated current of 16 Amps. And look at his time current characteristic.

Look carefully at the chart. You can see the effect of the current flowing at the time of disconnection. The X-axis indicates current fold (relative to the nominal current of the machine), resembling through automatic, and on the Y-axis shows the time off in seconds.

I highlighted in red region of the heat element (bimetallic strip), and the yellow region of the electromagnetic tripping operation.

Now let's model the following situation: Let's say the machine will proceed through the current 25 amps. This means the time of his trip is 50 minutes. In other words, if you overload the machine at 45% of face value, while it is 50 minutes off

Now let's assume that the current passes through the machine at 100 amperes. In this case, the heat will not work element and the solenoid trip unit and the trip time should be 0.01 seconds.

What machines are best used in the house

So, with features such as a more or less clear. Now let's find out what type of machine is preferable to put the home distribution board.

Of course, in the apartments and homes is better to use machines with characteristic "B", as the inrush current in a private home ownership is almost no. And the machine with characteristic "B" better protect your wiring from overheating.

Machines category "C" can also be installed in the household, but they are great to protect your network, only if the wiring in a building, all connections are high quality, but at home there is the power of Flawless line.

In the old fund, where the state of the network is poor, machines "B" is still preferable to use.

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