Automatic differential current switch: device and principle of operation of the difavtomat

Once upon a time, one-time fuses served as protection against overload in the electrical network - plugs, switching off of which was often ignored by consumers, then they began to install automatic switches. But the problem of comprehensive protection was not solved. The automatic residual current switch simultaneously protects the network from overload and from electric shock.

Device and principle of operation

Differential machine, or differential, is a modular device that combines the functions of several equipment: machines that protect the network from overload and short circuit, residual current device (RCD), which protects people from contact with an open or damaged wire.

All working parts of the diff are assembled in a dielectric case designed for installation in an electrical panel. These are the parts:

1. Release mechanism.
2. Release. A device consisting of an inductor and a metal core. The core is connected to a mechanism that provides closure during normal operation.
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3. A thermal release that opens an electrical circuit when a slightly higher current flows through it.
4. Reset rail.

The protective part is also a differential protection module, which is triggered when there is a current in the ground wires. In case of exceeding the norm, it gives a signal about the reason for the operation of the machine. The design of the module is represented by the following parts:

• differential transformer;
• amplifier;
• reset coil;
• control of the serviceability of the machine.

On top of the case there is a button for checking the device. To check the readiness of the dif for protection, you need to press the button, thereby provoking a trigger. The circuit is closed and the protection reacts to leakage current.

Current leakage can occur if the insulation of the electrical appliance is damaged. When using grounding, there is no increased voltage in relation to the ground on the machine case. When current passes through the ground wire, the resistance increases up to breakage. If the device is not grounded, there is a danger of electric shock.

The disadvantage of grounding is that it cannot control the integrity of the insulating wire. The principle of operation of the difavtomat is precisely that such control is carried out. Its protective part works on the principle of electromagnetic induction. An instrument transformer, which is used as a sensor, reacts to the difference in electrical currents at the input and output.

Parts of this device are also two windings connected towards each other. When a magnetic flux arises in the core, it provokes the appearance of a current in the secondary winding - this gives a signal to the protective mechanism, which opens the differential contacts.

Types of differential machines

Today, a large number of difavtomats are produced by various enterprises. In order to choose the right option, you need to know their classification according to their current characteristics. This will make it possible to compare them with each other and save your time.

Leakage current all residual current switches are divided into such groups:

1. Speaker type. The machine of this group is capable of responding to alternating current leakage. It appears in an instant or gradually. When the threshold value is exceeded, the difavtomat should work, and the protected line should be broken. In Europe, this type is almost never used. Any device is used in Russia.
2. Type A. These switches are more expensive than the first ones, as they are equipped with additional control of ripple currents. They are the most widespread and are recommended by specialists.
3. Type B. Differential switches belonging to this type are triggered by DC, AC or rectified current leakage, despite the threshold value. In most cases, they are used at industrial facilities.

By the time of the current trip, the difavtomatic circuit breakers belong to one of three classes. Each of them shows how many times the tripping current exceeds the rated current when the device is turned off. According to Russian standards, there are three such classes:

1. V. Class B devices turn off when the voltage rises 4-6 times in comparison with the nominal.
2. WITH. Devices with this designation are triggered when the norm is exceeded by 4-9 times.
3. D. The residual current circuit breaker of this group reacts when the rated current is increased by 10-20 times.

But no matter how quickly the releasers react, it lasts for some time. When the contacts are opened mechanically, an electric arc occurs for a time until the contact distance increases so much that the arc is no longer formed.

This data is very important for the normal operation of the electrical wiring. The dif works here like a circuit breaker, which protects the insulation from high heating of the wires. In this category there are three classes:

• Class 1 devices extinguish the arc for more than 10 ms;
• Class 2 devices have an arc extinction time of 4-9 ms;
• Differential class 3 produces blanking in 3-7 ms.

Differential switches are classified according to climatic data, nominal frequency and other characteristics. They are also electronic and electromechanical. Electronic ones are much more compact, but if there is no supply voltage on the board, they are inactive. This happens when the neutral wire breaks.

In this case, you need to turn off the power supply, but only an electromechanical type of device can help here. Outwardly, the devices are almost the same. You can find out with the help of the Krona battery: if you connect it without a differential transformer, an electromechanical automatic machine will work, but an electronic one will not.

Circuit breaker installation and scope

Installing a residual current circuit breaker is straightforward. First of all, you need to inspect the purchased device, whether there are any scratches or damage to the case. In the presence of cracks or other malfunctions, full protection will not be provided.

It is then attached to the Din-rail of the electrical panel using a latch located on the back of the enclosure. It is imperative to make grounding. After that, you need to check if the installed device is working. Under load, the "Test" button is pressed, and the switch should trip.

The main thing is to select the required number of amperes and make the correct calculation of the load on the network in order to avoid overload. Connection is possible according to the following schemes:

1. Difautomat is connected at the input. Such a connection will help to ensure the protection of all groups of the electrical circuit. In addition, this arrangement does not require a lot of space and is therefore inexpensive. But there is one drawback: when the machine is turned off, the current disappears in the entire network.
2. A separate differential is mounted on each circuit, which can protect all elements connected to it. Unlike the first scheme, only one group will be disconnected, which is much more convenient.

The use of differential switches is related to their purpose. A properly installed difavtomat by an electrician give a chance:

1. Ensure safety when the wire insulation is broken or a short circuit occurs.
2. Provide reliable protection against electric shock if a person accidentally touches open or damaged wires.
3. Prevent overheating and fire of damaged insulation in some places.
4. Provide guaranteed protection to the power supply system against the failure of its individual elements during overloads and short circuits.

One of the most reliable and popular brands in the market, ABB difavtomat is used to protect low-voltage household networks from overloads due to voltage surges and short circuits, which arise due to the large number of connections of powerful electrical appliances. The ABB circuit breaker provides protection even with prolonged exposure to leakage currents.