What is a difavtomat, what is it used for, diagrams, how to connect

From the article you will learn what a difavtomat is and what it is used for, what it is, the device and the principle of operation of the device, a circuit diagram, decoding of the symbols on the case, how to connect.

Safety is important

When designing and laying a low-voltage electrical network, one of the main tasks for specialists is to protect against short circuits and ensure the maximum level of safety.

To solve it, special devices are used, one of which is a differential automaton (difavtomat).

Consider the following questions below:

• What is this product?
• What is it used for, and what types of difavtomatov are there?
• What elements does it consist of, and how does it work?
• How to decipher the designations and connect the difavtomat?
• What are the reasons for triggering?

Definition difavtomata

A differential machine is a protective device that is installed in a low-voltage network to ensure its comprehensive protection.

In one device, two functions are combined – an automatic switch (cut-off) and an RCD.

Due to its advanced features, the product is in great demand in everyday life and at work.

Scope

Difavtomat is used to solve the following tasks:

• Protection of a certain section of the network from the flow of increased currents that occur in the event of a short circuit or overload.
• Prevent fire or people from getting under the influence of voltage due to the appearance of a leak that occurs due to poor-quality insulation of wires or failure of household appliances.

In the first case, the differential machine works as a circuit breaker, and in the second – as an RCD (residual current device).

What kinds are there?

The differential machine is a universal device that can be easily used in single- and three-phase networks.

In the first case, products with two poles are used, and in the second – with four.

Design features, principle of operation and diagram of the difavtomat

Considering the designation of the device according to GOST, it is easy to single out the structural elements of the protective apparatus.

The main ones should include:

• Differential transformer;
• Release group (thermal and electromagnetic).

Each of the elements performs certain tasks. Let’s consider them in more detail.

A differential transformer is a device with several windings, the number of which directly depends on the number of poles.

Its task is to compare the load currents in each of the conductors. In the event of a discrepancy between the indicators, a leakage current appears, which is sent to the starting body.

If the parameter is above a certain level, the device turns off the electrical circuit by separating the power contacts of the difavtomat.

To check the performance, a special button is provided, most often signed as “TEST”. It is connected through a resistance, which is connected in two ways:

• Parallel to one of the existing windings;
• Separate winding on the transformer.

After the button is triggered, the user artificially generates an unbalance current. If the difavtomat is working, it should turn off the circuit. Otherwise, conclusions are drawn about the malfunction of the device.

The next element of the difavtomat is an electric release. Structurally, it looks like an electric magnet with a core.

The purpose of the element is to act on the tripping mechanism. The operation of the electromagnet occurs when the load current increases above the set level.

Most often this happens when a short circuit occurs in a low-voltage network. The feature of the release is that it operates without a time delay. It takes a fraction of a second to turn off the power.

Unlike the electromagnetic one, the thermal release does not protect against short circuits in the circuit, but from overloads. The node is based on a bimetallic plate through which the load current flows.

If it is higher than the permissible value (nominal current of the difavtomat), a gradual deformation of this element occurs. At a certain moment, the bimetal plate gradually bends.

At a certain moment, it acts on the tripping element of the protective device. The time delay of the thermal release depends on the current and temperature at the installation location. As a rule, this dependence is directly proportional.

The lower limit is written on the casing of the difavtomat (indicated in mA). In addition to the leakage current, the rated current of the release is also indicated. We will talk in more detail about the labeling of the device below.

How to decipher the designations on the case?

It has already been noted above that all the necessary information can be found on the body of the differential machine.

Having studied the main parameters, it is easier to make a decision – whether the device is suitable for solving specific problems.

The most important notations include:

• RCBO is an abbreviation, an abbreviated version of the full name (“residual current circuit breaker”).
• C25 is the nominal current parameter. Here C is a characteristic of the dependence of time and current, and 25 is the limiting current of the difavtomat, the excess of which is unacceptable.
• 230 V is the rated voltage at which the device can be used (for a household network).
• In 30mA is the leakage current parameter. When 30 mA is reached, the RCD operates.
• A special sign that confirms the presence of the RCD function and the type of RCBO. By the presence of the designation, a conclusion is made about the ability of the differential machine to respond to direct or alternating pulsating current.

Also on the body of the protective product is a circuit diagram. She may not tell anything to the average layman, so it is not necessary to pay attention to her.

Also on the outside of the device there is a button “TEST”, which is necessary for periodic monitoring of the health of the device in terms of the RCD. We have already talked about the features of checking using this element above.

How to connect the device?

Before connecting a difavtomat, it is worth understanding the type of electrical wiring.

The following options are possible here:

• Network type – single-phase or three-phase. In the first case, the nominal voltage will be 220 volts, and in the second – 380.
• The presence of grounding – there are networks with or without grounding.
• Place for installation. Most often, RCBO is installed in an apartment, but installation on each individual group of conductors is possible.

Taking into account the conditions considered, it is necessary to decide how to connect the protective device. It is worth remembering that the difavtomat may have a number of design differences.

Consider the main connection methods in the shield:

1. The simplest version. A popular way is to install one differential machine that protects the entire chain. When choosing this option, it is advisable to buy a difavtomat with a large rated current in order to take into account the load of all consumers in the apartment. The main disadvantage of the circuit is the difficulty in finding the fault location when the protection is triggered. In fact, the problem may be hiding in any of the wiring sections.In the above diagram, it can be seen that the “ground” goes separately and is combined with the ground bus. All conductors (PE) from electrical appliances are connected to it. Of key importance is the connection of “zero”, which is withdrawn from the difavtomat. Its association with other “zeros” of the electrical network is prohibited. This is due to the difference in the magnitude of the currents passing through each of the neutral conductors, due to which the differential machine can work.
2. Reliable protection. This is an improved option for connecting a protective device, thanks to which it is possible to increase the reliability of the network and simplify the task of finding damage. The peculiarity lies in the installation of a separate difavtomat for each group of wires. Therefore, the protective device will only work in the situation when a problem occurs in the controlled section of the circuit. Other sections will continue to operate as usual. Unlike the previous scheme, it is much easier to find a malfunction in the event of a short circuit, a leak or an overload in the network. But there is also a drawback – the large financial costs associated with the need to purchase several difavtomatov.
3. Circuit without grounding. The options for connecting a difavtomat discussed above imply the presence of a protective “ground”. But in some houses or in a summer cottage, there is no ground loop at all. In such networks, a single-phase network is used, where there is only a phase and “zero”. In this situation, the protective device (AVDP) is connected according to a different principle. If you also do not have a “ground” in the low-voltage network, it is advisable to completely change the wiring in the house before installing the difavtomat. Otherwise, there may be a leakage current in the network, due to which the RCD will operate.
4. Scheme for a 3-phase network. In cases where the installation of a differential device in a three-phase circuit is required (for example, in a modern apartment, in a house or in a garage), an appropriate ARFS is required. The principle of construction here is the same as in the previous case. The difference is that four wires must be connected at the input and output.

For what reasons can a difavtomat work?

During the operation of a protective device, it is important to understand in which cases it can work.

Taking into account these nuances, it is worth deciding on the cause of the problem (short circuit, leakage current, etc.).

Let’s consider each of the options in more detail:

Operation without load.

In older, poorly wired houses, there are serious insulation problems.

The latter is worn out and there is a high risk of leakage currents, the magnitude of which can vary depending on many parameters – the presence of humidity levels near animals, and so on.

In such a situation, the AVDP may work falsely.

The cause of the problem may be:

• Damaged insulation;
• The presence of twists;
• Miscalculations in the location of distribution boxes;
• Electrical accessories.

A wiring revision is required to identify the cause. It is necessary to start with the diagnosis of the damage site.

For example, if the difavtomat knocks out when the light is turned on, the problem must be sought in the lighting circuit.

If the AVDP works after connecting any device to the outlet, you should make sure that this device is working properly.

When closing “zero” and “ground”.

If, for any reason, the N and PE wires touch each other, the risk of tripping the differential machine is high. Common places of short circuits are in the junction box or in the box for the outlet.

Read on the topic – effective ways to protect electrical appliances using special devices.

The triggering logic is built on the principle of the device. If “zero” and “ground” are combined, the current is divided between the two conductors. Accordingly, there is no equality of currents in the differential transformer, and it perceives this fact as a leak.

The problem is often faced by novice craftsmen who do not have the proper experience in maintaining a difavtomat.

1. When the load is turned on. If the ARFS operates when the load is connected, the problem must be sought in isolation. Using wiring with such a malfunction is unsafe, so it is recommended to call a specialist and deal with the problem. If it is ignored, there is a high risk of one of the family members getting under voltage or a fire.
2. With power surges. The difavtomat logic is designed in such a way that a shutdown can occur in the event of an increase in voltage. True, not all devices have this option, but only those with an electronic circuit. In addition, the protection can work with a short circuit inside the consumer, because the difavtomat can turn off in this type of accident.

Read on the topic – how does electric current affect the human body.

Results

A differential machine is a useful device that can protect against short circuits and leakage currents in a low-voltage network.

For its correct use, it is important to know the rules for connecting and operating, as well as the features of diagnosing a malfunction in the event of an operation of the device. It is useful to read – how to install electrical wiring in a wooden house.