Short circuits occur in any electrical installations, regardless of their complexity. Even if the electrical wiring is new, lamps and sockets are good, and electrical equipment is released by the manufacturers known to the whole world, no one is insured against short circuits. And they need to be defended.

Devices for protection against emergency modes on the network

Fuses are the simplest protection devices. Previously, to eliminate emergency modes in household wiring, only them were used. In some devices, fuses are used to this day. Cause - they have high speed and are indispensable to protect semiconductor devices.

After the response, the fuse is either replaced with a new one or inside it is changing fusible insert. Inserts for the same fuse housing are available on different currents. But the need to keep on the facility or in the apartment, the stock of fuses for operational replacement is a lack of fuses.

The most common fuse in Soviet times was "traffic jam".

Fuse - "Cork"

On the change they came automatic tubes like ParThe currents of 10, 16 and 25 A. they were produced on the velocity of the plugs were reusable and had two protective elements called releasers. One defended OT. short circuits And instantly worked, the second - from overload and triggered with time delay.

The same releasers have all automatic switcheswho have replaced fuses. Instant release is called electromagnetic, Because the basis of its work is the principle of pulling the coil rod when the rated current is exceeded. The rod strikes the latch and the spring opens the contact system of the switch.

The releaser, acting with the excerpt of time called thermal. It works on the principle of the thermostat in the iron or electric heater. Bimetallic plate When passing through it, the current is heated and slowly bent to the side. The more current through it, the faster the bend occurs. Then it acts on the same latch, and the machine is turned off. If the exposure of the current has stopped, the plate cools, returns to its original position, and does not turn off.

In old electrical panels, automatic switches in the carbitone case of types A-63, A3161, or more modern AE1030, are still preserved. But all of them no longer satisfy modern requirements.

They are worn, and their mechanical part or rusted, or lost the speed. And not in each of them there is instantaneous protection against short circuit. Some devices were installed only a thermal release. Yes, and the speed of operation of the electromagnetic release in the automata of these series is lower than that of modular.

Therefore, such protective devices need to be changed to modern until they have done their inactivity.

Properties of protection

In apartment buildings, the machines are installed in the panel on the staircase. To protect the apartments of this enough. But if you have installed a personal shield when replacing electrical wiring, it is better to install a personal automatic for each consumer group. There are several reasons for that.

1. When replacing the socket, you will not need to turn off the light in the apartment and use the flashlight.
2. To protect some consumers, you will reduce the rated current of the machine, which will make their protection more sensitive.
3. When damaged in the electrical wiring, you can quickly disable the emergency area and leave the rest in operation.

In private homes, bipolar switches are used as input. This is necessary for the case of erroneous switching to the substation or line, as a result of which the phase will be on the zero place. The use of two single-pole switches for this purpose is unacceptable, since the one can turn off that in zero, and the phase will remain.

It is impractical to the use of a three-pole switch as an equivalent of three single-pole. Removing a plank that combines three poles will not help. Inside the switch there are thrust disconnecting the remaining poles when one of them is triggered.

When using the UZO, be sure to protect the same line and the circuit breaker. Uzo protects against leakage currents, but does not protect against short circuits and overloads. The function of protection against leakage and emergency modes of operation is combined in the differential machine.

Selecting automatic switches

When replacing the old circuit breaker, install the new nominal current. According to the requirements of the energy sales, the nominal switch of the switch is received, based on the maximum allowed load.

The distribution network is arranged in such a way that with the approach to the source of power supply, the nominal currents of protection devices are increasing. If your apartment is turned on through a single-phase circuit breaker 16 A, then all apartments in the entrance can be connected to a three-phase machine for 40 A and evenly distributed by phases. In the event that, with a short circuit, your automatic will not turn off, after some time, the overload will work in the accession. Each subsequent protective device reserves the previous one. Therefore, it is not necessary to overestimate the value of the rated current of the circuit breaker. It may not work (not enough current) or turn off with a group of consumers.

Modern modular circuit breakers are available with characteristics "B", "C" and "D". They differ in the multiplication of currents of the cut-off.

Be careful with the use of automata with the characteristics "D" and "B".

And remember: if short circuit does not disable, it will lead to a fire. Take care of protecting the protection, and live calmly.

Almost everyone in his life came across a short circuit. But most often it happened like this: a flash, cotton and that's it. This happened only because there was a short circuit protection.

Short circuit protection device

The device can be an electronic, electromechanical or simple fuse. Electronic devices are mainly used in complex electronic devices, and we will not consider them within this article. Let us dwell on the fuses and electromechanical devices. Fuses were first used to protect the household power supply. We are accustomed to see them in the form of "plugs" in the electrical protection.

There were several types of them, but all the protection was reduced to the fact that inside this "traffic jam" was a thin copper wiring, which broke out when a short circuit occurred. It was necessary to run to the store, buy a fuse or store at home, perhaps not soon the resulting stock of the fuses. It was uncomfortable. And automatic switches appeared on the light, which first looked like "plugs".

It was the simplest electromechanical circuit breaker. They were produced on different currents, but the maximum value was 16 amps. Soon, higher values \u200b\u200bwere required, and technical progress made it possible to produce automata that we now see them in most electric flaps of our homes.

How does the machine protect us?

It costs two types of protection. One type is based on induction, the second on heating. A short circuit is characterized by a large current that flows along a short-circuit chain. The machine is arranged in such a way that the current flows through the bimetallic plate and the coil of inductance. So, when a high current flows through the machine, a strong magnetic flux arises in the coil, which leads to a movement mechanism of a quilted machine. Well, the bimetallic plate is designed to flow the rated current. When the current flows on the wire, it always causes heating. But we often do not notice this, because heat has time to dispel and it seems to us that the wires are not heated. The bimetallic plate consists of two metals with different properties. When heated, these both metal are deformed (expand), but since one metal is expanding stronger than the other, the plate begins to bend. The plate is selected in such a way as to exceed the nominal value of the automaton, due to the bending, it operated the release mechanism. Thus, it turns out that one protection (inductive) operates on short circuit currents, and the second for currents, long-flowing through the cable. Since short-circuit currents are rapid character and proceed in a network short period of time, the bimetallic plate does not have time to warm up to such an extent to deform and turn off the machine.

Short Circuit Protection Scheme

In fact, nothing complicated in this scheme. The chain is set, which disables either the phase wire or the entire chain. But there are nuances. Let us dwell on them.

1. You can not put individual automata in the phase chain and the zero chain. For one simple reason. If suddenly, with a short circuit, the zero automatic will turn off, then the entire power grid will be under voltage, because the phase machine will remain on.
   
2. You can not install a smaller wire, which allows the machine. Very often in apartments with old wiring to increase power, put more powerful automata ... Alas, it is the most common cause of short circuits. This is what happens in such cases. Suppose, for clarity, there is a wire, copper, cross section of 1.5 square meters, which is able to withstand the current up to 16 A. Automatic machine 25a. We turn on the load to this network, say 4.5 kW, a current of 20.5 amps will flow along the wire. The wire will begin to warm themselves, but the machine will not turn off the network. How do you remember, the machine has two types of protection. Short-circuit protection does not work yet, because there is no short circuit, and the nominal protection will work at a value exceeding 25 amps. So it turns out that the wire is warmed up, isolation begins to melt, but the machine does not work. In the end, there is a breakdown of isolation and a short circuit appears and the automatic is finally triggered. But what would you get? The line can not be used more, it must be replaced. It is easy if the wires are laid in an open way. But if they are hidden in the wall? New repair is provided to you.
3. If the aluminum wiring is more than 15, and copper for more than 25 years, and you are going to make repairs - clearly change the new wiring. Despite the investment it will save you money. Imagine that you have already done repairs, and in some disintegration box turned out to be bad contact? This is if we talk about a copper wire (which, as a rule, it makes only an insulation or connection site over time oxidize or weakened, then begin to warm up, which further leads to the destruction of the twist). If we talk about aluminum wire, then still worse. Aluminum is a very plastic metal. When fluctuations in temperatures, compression and extension of the wire are quite significant. And if there was a microcrack (factory marriage, a technological marriage), then over time it increases, and when it becomes quite large, which means the wire in this place is thinner, then when current flows, this area begins to warm up and cool that only speeds up the process . Therefore, even if it seems to you that everything is fine with the wiring: "After all, it worked before that!", - Better, still change.
4. Swamp boxes. There are articles about it, but in short, I will walk here on them. Never make scrubs !!! Even if you make them well, this is a twist. The metal has a property to shrink and expand under the influence of temperature, and the twist is weakening. Try not to use screw clamps for the same reason. Screw clamps can be used in open wiring. Then, at least, you can periodically look in the boxes and check the condition of the wiring. Warm-type "WAGO" type screw clamps are best suited for this purpose, the "Walnut" screw clamps are best suited for power wiring (there are two plates that are tightened by four screws, in the middle another plate, Those. With the help of such clamps you can connect copper and aluminum wires). Leave the reserve of the stripped wire at least 15 cm. It pursues two goals: if there is a bad twist contact, the wire has time to dispel heat, and you have the opportunity if you remake the twist. Wires try to locate in such a way that there are no overhells between phase and zero with grounding. Wires can crossed out, but do not lie on each other. Try the twist point in such a way that the phase wire is on one side, and zero and grounding into another.

   

5. Do not connect directly copper and aluminum wires. Either use the "WAGO" terminals, or the "Walnut". This is particularly relevant about wires intended for connecting electric stoves. Usually, when they make repairs and transfer the rosette for the plates, the cable is increasing. Very often it is aluminum wires that increase copper.
6. A little special. Do not save on switches, sockets (especially for electric stoves). The fact is that at the present time to find good sockets for electric plates to find quite difficult (I'm talking about small cities), so it's best to either use the "Walnut" U739m compressions, or find a good outlet.
7. When tightening the terminals on sockets, make it stronger, but do not make the thread, if it happened, it is better to change the socket at once, do not hope for "avos."
8. When laying a new electrical track, use the standards: 10-15 cm from corners, ceiling, walls (by sex), shoals, window frames, floor (over the wall). With this, you will protect yourself when installing, for example, suspended ceilings or plinths that are attached with the help of a dowels for which the hole must be pierced. If the wire is in the corner between the floor and the wall, it is very easy to get into the wire. All wires must be located strictly horizontally or vertically. So it will be easier for you to understand where you can continue the new hole, if you suddenly need to hang the shelf or picture or TV.
9. Do not connect the loop (from one to the other) more than 4 sockets. In the kitchen, I do not recommend connecting more than two at all, especially where it is planned to use the oven, kettle, dishwasher and microwave in one place.
10. The overall wardrobe is best laying out a separate line or connect it to the line from which the cooking surface feeds (for it is often consumed about 3 kW.) Not every socket is able to withstand such a load, but if another powerful consumer will be connected to it ( For example, a kettle), you risk getting a short circuit due to strong heating of the connection in the slot of the loop.
11. Try not to use extension cords to include powerful electrical appliances, such as oil heaters, or use extension cords of well-known manufacturers, and not Chinese NO NAME. Read carefully what power is able to save this extension cord, and do not use it if it costs less power than you need to be powered. When using the extension cord, try to avoid twisted wires. If the wire simply lies, it has time to dispel heat. If the wire is twisted, then heat does not have time to dissipate and the wire begins to heat up significantly, which can also lead to a short circuit.
12. Do not turn in one outlet (through a tee or extension with several sockets) at once somewhat strong consumers. A good outlet is allowed to turn on the load of 3.5 kW, for not very good up to 2 kW. In homes with aluminum wiring to any rosette no more than 2 kW, and even better on a group of sockets that feed on one machine do not include more than 2 kW.
13. Before putting into each room on the heater, make sure the rooms are seized from different automata. As the saying goes: "And the stick can sometimes shoot," as well as with automatic machines: "And the machine can sometimes not work," and the consequences of this pretty cruel. Therefore, secure yourself and loved ones.
14. Carefully contact the heating devices, make sure that the wire does not hit the heating elements.

Short circuit protection machine

Why did I undertake this separate item? Everything is simple. It is the machine that provides protection against short circuit. If you install, then it is necessary, after you need to put an automatic machine, or put immediately (this is the device two in one: Uzo and automatic). Such a device disables the network and with a short circuit, and when the nominal value of the current is exceeded, and with a leakage current, when, for example, you turned out to be energized, and electric current began to flow. Let me remind you again: the RCO does not protect against short circuit, the RCD protects you from electric shock. Of course, it may also be that the RCO will turn off the network with a short circuit, but it is not intended for this. The triggering of the UZO with a short circuit is absolutely random. And it can burn all the wiring, it can be all in the flame, and the Uzo will not turn off the network.

Similar materials.

Presented design protection for the power supply of any type. This protection scheme can work together with any power supply - network, pulse and DC batteries.

A schematic disunity of such a protection block is relative and consists of several components.

The power part is a powerful field transistor - during the work does not overheat, therefore does not need it in the heat sink either.

The scheme is simultaneously protected from measuring reversal, overload and KZ. At the output, the triggering current can be selected by the selection of resistance of the shunt resistor, in my case the current is 8amper, 6 resistors 5 watts 0.1 ohms parallel to connected.

Shunt You can also be made from 1-3 watt resistors.

More precise protection can be adjusted by selecting the resistance of the trim resistor.

When CW and overloading the output of the block, the protection instantly will work, turning off the power supply. The LED indicator will inform about the protection of protection. Even with a CZ exit for a couple of tens of seconds, the field transistor remains cold.

The field transistor is not critical, any keys with a current of 15-20 and above ampere and with a working voltage of 20-60 volts are suitable. Excellent line keys IRFZ24, IRFZ40, IRFZ44, IRFZ46, IRFZ48 or more powerful - IRF3205, IRL3705, IRL2505 And they are similar.

This scheme is also perfect as the protection of the charger for car batteries, if the polarity of the connection suddenly was confused, then nothing terrible with the charger will occur, the defense will save the device in such situations.

Thanks to fast protection, it can be successfully applied for pulse schemes, with short-circuit protection will work faster than the power keys of the pulse power supply unit will have to burn. Schematics will also be suitable for pulse inverters, as current protection. When overloading or KZ in the secondary chain of the inverter, the power transistors of the inverter fly through the moment, and such protection will not give it to happen.

Regards - Aka Kasyan

Many homemade blocks have such a disadvantage as the lack of protection against meals. Even an experienced person can interpret the polarity of food. And there is a high probability that after that the charger will be unusable.

This article will consider 3 options for stir protectionthat work reliability and do not require any adjustment.

Option 1

This protection is most simple and differs from similar in that it does not use any transistors or chips. Relay, diode alert - that's all its components.

The scheme works as follows. Minus in the general scheme, therefore a plus chain will be considered.

If the battery is not connected to the input, the relay is in open condition. When connecting the battery, the plus comes through the VD2 diode on the relay winding, as a result of which the relay contact closes, and the main charge current proceeds to the battery.

At the same time the green LED indicator lights up, indicating that the connection is correct.

And if you remove the battery now, then the output of the circuit will be the voltage, since the current from the charger will continue to arrive through the VD2 diode on the relay winding.

If you confuse the polarity of the connection, then the VD2 diode will be locked and no power will be switched to the relay winding. The relay will not work.

In this case, the red LED will light up, which is deliberately connected in the wrong way. It will indicate that the polarity of the battery connection is broken.

The VD1 diode protects the chain from self-induction that occurs when the relay is turned off.

In case of introducing such protection in , It is worth taking the relay on 12 V. The allowable current relay depends only on power . On average, it is worth using a relay by 15-20 A.

This scheme still has no analogues in many parameters. It simultaneously protects both the power cords and from short circuit.

The principle of operation of this scheme is next. Upon normal operation, plus from the power source through the LED and the R9 resistor opens the field transistor, and minus through the Open Transition of the Bevelika enters the output of the circuit to the battery.

When reformed or short circuit, the current in the circuit increases sharply, as a result of which the voltage drop on the "wildfather" is formed and at shunt. Such a drop voltage is enough to trigger a low-power transistor VT2. Opening, the latter locks the field transistor, a closing shutter with a mass. At the same time, the LED lights up, since the power is provided to the open transistor VT2 transistor.

Due to the high response rate, this scheme is guaranteed to protect With any problem at the output.

The scheme is very reliable in operation and is able to remain in a state of protection indefinitely for a long time.

This is a particularly simple scheme that is even difficult to name the scheme, since it uses only 2 components. This is a powerful diode and fuse. This option is quite viable and even applied on an industrial scale.

Power from a charger through a fuse enters the battery. The fuse is selected based on the maximum charging current. For example, if a current is 10 A, then the fuse is needed by 12-15 A.

The diode is connected in parallel and closed at normal operation. But if you confuse polarity, the diode will open and happen short circuit.

A fuse is a weak link in this scheme that burns into the same moment. His after that will have to change.

The diode should be chosen on a datashet based on the fact that its maximum short-term current was several times the fuse's combustion current.

Such a scheme does not provide one hundred percent protection, since there were cases when the charger burned the fuse faster.

Outcome

From the point of view of the efficiency, the first scheme is better than others. But from the point of view of universality and response rate, the best option is a circuit 2. Well, the third option is often used on an industrial scale. This option can be seen, for example, on any car radio.

All schemes, besides the last, have a feature of self-restoration, that is, the work will be restored as soon as the short circuit will be removed or the polarity of the battery connection will change.

Attached files:

How to make a simple turn bank with your own hands: Scheme of homemade Power Bank

Presented design protection for the power supply of any type. This protection scheme can work together with any power supply - network, pulse and DC batteries. A schematic disunity of such a protection block is relative and consists of several components.

Power Supply Scheme

The power part is a powerful field transistor - during the work does not overheat, therefore does not need it in the heat sink either. The scheme is simultaneously protected from supplying the power supply, overload and KZ at the output, the trigger current can be selected by selecting the resistance of the shunt resistor, in my case the current is 8 amps, 6 resistors are 5 watts 0.1 ohms parallel to connected. The shunt can also be made of resistors with a capacity of 1-3 watts.

More precise protection can be adjusted by selecting the resistance of the trim resistor. Power supply protection circuit, current limit control circuit protection diagram, current limit control

~~~ with a CW and overloading of the block output, the protection instantly will work, turning off the power supply. The LED indicator will inform about the protection of protection. Even with a CZ exit for a couple of dozen seconds, the field transistor remains cold

~~~ The field transistor is not critical, any keys with a current of 15-20 and above ampere and with a working voltage of 20-60 volts are suitable. The keys from the IRFZ24, IRFZ46, IRFZ44, IRFZ46, IRFZ48 or more powerful - IRF3205, IRL3705, IRL2505 and them are similar are excellent.

~~~ This scheme is also great as the protection of a charger for automotive batteries, if the polarity of the connection suddenly was confused, then nothing terrible with the charger will occur, the defense will save the device in such situations.

~~~ Thanks to rapid protection, it can be successfully applied for pulse schemes, with a short-circuit protection will work faster than they will have to burn the power keys of the pulse power supply. Schematics will also be suitable for pulse inverters, as current protection. When overloading or KZ in the secondary chain of the inverter, the power transistors of the inverter fly through the moment, and such protection will not give it to happen.

Comments
Short circuit protection, surprise polarnosi and overload is assembled on a separate board. The power transistor was used by the IRFZ44 series, but if desired, it can be replaced with a more powerful IRF3205 or any other power key that has close parameters. You can use the keys from the IRFZ24 line, IRFZ40, IRFZ46, IRFZ48 and other keys with a current of more than 20 amps. During the work, the field transistor remains ice,. Therefore, the heat sink does not need.

The second transistor is also not critical, in my case a high-voltage bipolar transistor of the MJE13003 series is used, but the choice is large. The protection current is selected based on the resistance of the shunt - in my case 6 resistors in 0.1Ω parallel, the protection is triggered with a load of 6-7 amps. You can more accurately configure the rotation of the variable resistor, so I set up a trigger current in the region of 5 amps.

The power of the power supply is quite decent, the output current comes to 6-7 amps, which is enough to charge the car battery.
Schunts resistors chose 5 watts with a capacity, but it is possible for 2-3 watts.

If everything is done correctly, the unit begins to work immediately, closure the output, the LED indicator of the protection will light up, which will be lit until the output wires are in the KZ mode.
If everything works as needed, then proceed on. We collect the scheme of the indicator.

The scheme is drawn from the battery charger. The red indicator suggests that there is an output voltage at the output of the BP, the green indicator shows the charging process. With such a layout of the components, the green indicator will gradually swell and will finally go out when the voltage on the battery will be 12.2-12.4 volts, when the battery is disabled, the indicator will not burn.