For what automatic cuts are necessary?
The Automatic Cut (AC) is not similar at all on normal which is located in each room of your cozy dwelling for inclusion and switching off of light. Its task consists a little in another. It is intended for protection of electric circuits against the short circuit, voltage variation, overloads and other violations of operating modes of the chain and also for manual shutdown and switching off of lines and consumers of electricity.
Presently, when technical progress does not stand still, AV from bulky, a little inconvenient the switching device turned in compact (as far as it is possible).
Automatic machines (as it is accepted to call this device) most often are installed on the entrance to the house or to the apartment. Also try to place them in special boxes (boards) which can be both metal, and plastic.
There are many versions AV. Some of them serve only as switches of the chain and for protection of network from the overload, and some have additional functions, for example protection against currents of the lowered loading.
All AV on response time on inadmissible tension are subdivided into three look:
- the selection;
Response time of the normal automatic machine fluctuates from 0,02 to 0,1 pages. In the selection AV this same time. High-speed AV work a little quicker: at them this size is only 0,005 pages.
All AV are put into the plastic unbreakable body with special fastening on the back party. It is very easy to install the automatic machine on this fastening, it is enough to insert of it on the rail in the board before click. It is so simple to remove the automatic machine – having pulled the screw-driver for the special ear. On the workmanship AV happen the different look, from single-pole to quadripolar, to different modifications.
In the automatic machine the so-called stuffing, that is its main safety devices – the electromagnetic and thermal releaser is located.
Main requirements to AV
In all automatic machines the main contact system has to:
- To provide, without overheating and without being oxidized, the long operating mode at rated current intensity.
- Without being damaged, to disconnect the chain at KZ currents.
Principle of work
For short circuit protection in AV there is the electromagnetic releaser. Electric current proceeds through the magnet coil. If current intensity exceeds the established value, the electromagnet attracts to itself contact which puts the disconnecting mechanism in action. High-speed releasers react to current of bigger force at KZ.
For overload protection the thermal releaser is provided. It represents the bimetallic plate which heats up when on it current proceeds. If current is too big, the plate overheats and deformed, thereby disconnecting the electric circuit. Releasers of this type work not at once, and with the delay. Current of KZ is capable to destroy this device.
Distinctions of AV
Automatic machines are distinguished on sensitivity degree to shutdown operation. In the most widespread standard models AV with the threshold value approximately equal of 140% of rated are most often applied.
AV is distinguished also by quantity of poles. What does it mean? In one automatic machine can be several electric lines independent from each other which are connected among themselves by the general mechanism of shutdown. For example, bipolar or triple-pole automatic machines (about what it was already mentioned above).
AV have distinctions and on other not less important indicators. They differ on the threshold current intensity which they pass through themselves. That the automatic machine could work and in the emergency to switch-off the power supply network, it has to be ready for the certain threshold of sensitivity. Such setup is usually made by the manufacturer and therefore on the automatic machine write numerical value of this threshold at once.
For domestic needs use automatic machines with indicators 3, 6, 10, 13, 16, 20, 25, 32, 40, 50, 63, 80, 100, 125 and 160 And. These digits mean the total power of all consumers of electric current who will be connected to the chain. The sensitivity of the automatic machine needs to be calculated not only on the total power of expected power consumers, but also wiring, and wiring products – switches and sockets. The table of types of automatic machines is included below.
Ranges of currents of instant unhooking of automatic machines of different types
Here the number of schedules which will be interesting to you is given (letters B, C, D designate areas of currents of instant unhooking).
Type B – over 3 I to 5 I inclusive.
Type C – over 5 I to 10 I inclusive.
Type D – over 10 I to 20 I inclusive.
Certain producers have additional curve shutdowns:
Type A – over 2 I to 3 I inclusive.
Type K – over 8 I to 14 I inclusive.
Type Z – over 2 I to 4 I inclusive.
The rated current (the I number) is understood as the current established by the manufacturer which the automatic machine is capable to carry out in the long mode at the control temperature of 30 °C.
The choice like AV
At the choice of the automatic machine recognize that its rated voltage has to be higher or to equally rated voltage of network. Determine (by means of mathematical calculations) the maximum current intensity of KZ in the protection zone, and choose the maximum permissible current intensity of AV more than this size.
Rated current intensity of the releaser has to be slightly more value of current intensity of the long maximum load, otherwise the automatic machine will disconnect the chain not only at disconnection of current intensity from the preset value, but also at the standard duty of work (if to tell simply, will work from each your sneeze).
It is also necessary to provide selectivity (selectivity) of operation of the automatic machine. It has to disconnect the protected object earlier, than other automatic machines of protection located closer to the power source. Protection is considered selective if characteristics of operation of devices of protection of the highest and lowest step of network taking into account zones of dispersion of characteristics are not crossed. The schedule where at the highest and lowest step automatic machines are located is included below.
As you see according to the schedule, in this case apply at the highest step (digit 1) of AV network with the increased adjustable response time (dotted curve) or at the lowest step of network current-limiting AV (dotted curve).
Purchase of AV
Several councils how to get AV in shop are competent:
- Buy AV in specialized shops, but not in the markets (you remember that the avarice is inappropriate here).
- Before purchase ask the seller to turn on the automatic machine, and let it will close upper and lower contacts of the automatic machine probes from the tester. At the same time the tester has to be included on the sound signal. If you heard the sound, so the automatic machine working. It is necessary accidentally not to buy the rejected automatic machine.
- Pay special attention that on the body there were no cracks and chips.
- On AV there has to be the sign of Rostest.
- There shall be the marking, and it has to be located exactly as industrially marking is put by the machine.
- Many producers release AV with the possibility of connection of additional contacts and with the possibility of connection of phase combs from above now.
- Rated voltage in volts shall be specified.
- The maximum disconnecting ability in amperes has to be specified.
- The selectivity class has to be specified.
- If you buy products of the German production or products made according to the German license, pay attention to signs which have to be specified AV. Designations which to you can meet are given in article.
In conclusion – the number of useful tables.Top