RCD: what it is, the device, the operating principle, selection and connection

We can not imagine life without electricity. He gives us heat, shineAnd, most importantly, it creates a comfortable environment. On the other hand, almost everyone knows that the electrical current under certain circumstances is very dangerous to life. How can you protect yourself? For this there are special automatic device, whose task is to turn off the electric current in case of any troubleshooting in the electrical network or human touch uninsulated parts of the circuit. To one of such devices and related "apparatus breakers" for short - RCD. What is it try to find out in this review.

RCD: what it is, device and function

RCD - an automatic device designed to protect the human or animal body by action of the electric current. This device stops the supply of electric current in case of:

• disruption of the power supply,
• any damage to electrical appliances,
• Insulation violations
• Accidental touching uninsulated electrical parts.

The main operating element of the RCD is a sensor, which is a transformer with a toroidal core. Trip threshold is set at magnetoelectric relay current. This relay has the function of supervisory authority and has high sensitivity.

Note! The new models instead uses special electronic circuitry. Such schemes are structurally electronic boards.

The third is a constructive part of the actuator RCD. Explained in detail what it is. The actuator - a device consisting of a coil spring and the contact group. The design provides self-test mechanism is its efficiency. "Test" button is displayed for this panel. By clicking on the button in the circuit creates an abnormal mode, which is captured by the current sensor, the impulse is then transmitted to the controlling relay and already it gives a command to the executive body on the functioning of the device, ie. e. power outage. Such self-examination should be carried out not less than 1 time per month.

Now let's see how this works:

• Normal mode. The electrical network is loaded, for the phase and the neutral conductor passes load, damage to circuit no current there are no leaks. Under these conditions, the current flowing in phase and the neutral conductor, the magnetic fluxes are generated which are directed oppositely to each other. These flows are equal in magnitude but opposite in sign. Consequently, the opposite direction flows will offset each other. Thus, the secondary side current of the transformer will also be zero. In the absence of the load controls the relay will not operate. This unit operation is called the initial mode.

• Abnormal RCD mode - what it is and when there? Such a regime can occur in the following cases:

1. accidental human contact with uninsulated portion electrical network energized;
2. in case of damage to insulation in household appliances, followed by closure of the housing;
3. decrease in insulation of electrical networks to dangerous quantities.

When abnormality in the mains mode appears capacitive, inductive or active current leakage. These currents produce phase currents that differ in size. The sum of these flows is different from zero. Therefore, these two streams do not compensate each other. This leads to the fact that part of the magnetic flux induces a voltage of the third winding of the transformer. Since this coil is closed to the controlling relay, then it starts to coil current flows, which will trigger the relay. When triggered, the relay contacts are closed and it will be given a selenoid pulse to the actuator. Selenoid release the lock latch trigger. The trigger releases the spring, and this will result in the opening of the main contacts and the cessation of the passage of electric current across the network.

RCD or differential Machine: how to distinguish and to choose

Most people uninitiated in the intricacies of human protection against electric shock, do not know the difference from a differential RCD machine. Thus, even some young professionals are not always able to explain it. We try to figure out the difference between ouzo and the differential machine.

As already noted, the RCD is established primarily to protect people from electric current actions. It interrupts passage of an electric current in the event of its leakage. The apparatus may also control the state of the insulation in the electric network. When certain settings it can respond to the decrease in the insulation to dangerous quantities. But it is not designed to react if a short circuit or overload occur on the network. In order not to cause a fire or damage to the equipment during process Abuse mains, should be from the power source to set automatic switches. Thus, to protect the power supply or electrical appliances of all kinds of short-circuit and overloads applied differential machine, and to protect against electric shock is applied RCD. This is the difference from the Emergency circuit breakers RCD.

marking

Markings applied to the RCD the housing. It shall include:

1. type of;
2. voltage in volts;
3. permissible load current in amperes;
4. differential current in milliamperes;
5. allowable operating temperature.

The housing must also be applied electric wiring diagram and RCD machine. Also, specify the types of RCD, which are marked with the following letters AU, A, B. The letters indicate what kinds of stresses calculated these devices.

When the marking indicates the letters "AC", it means that the RCD is designed for alternating current. The marking of this type is indicated by a wavy line. device type "A" intended for a network pulsating DC and AC. The mark on the undulating and convex lines. RCD type "B" used to work in networks of all kinds of currents. Indicated by the solid and dashed lines.

Related article:

a voltage regulator 220 for the house. The article deals with the selection criteria, the instrument impact on the different techniques, an overview of different models, especially the connection as to repair the device with your hands and much more.

Key Selection Criteria

When choosing to be guided by these basic criteria:

• genus electric current: AC, DC, pulsating. Based on this selected AS type device A or B;
• rated current of the RCD. It characterizes the maximum power that can be passed through a device power contacts;
• the number of poles. Number of poles determines to which power is intended RCD: single-phase or three-phase. If a single-phase network, the device must be in a bipolar design. If the three-phase network, the device is selected in the four-pole version;
• the presence or absence of delay when disconnected. RCD can disable the electricity network almost instantly, without any time delay. But it can occur off with a time delay. The delay time is set by setting a time set point. Thus, the structure of the RCD on the types and different delay time or without delay when disconnected.

Important! Experts recommend calculation settings, select the type of RCD, installation, testing and verification by a professional organization that has a license to carry out such work.

Review of well-known manufacturers and brands

In the market of electrical equipment is a lot of professional and reliable manufacturers. The main ones are:

• ABB. This Swedish-Swiss manufacturer of electrical equipment. The equipment of this manufacturer of high quality and reliability. Unit Price within 800-3000 rubles;
• The company is located in France. Unit Price within 1300-6500 rubles;
• The French manufacturer, has long operated in the Russian market. Unit Price within 550-12200 rubles;
• The American firm. The company competes with the previous companies in quality. Unit Price within 510-8000 rubles;
• The company is Germany. The quality is slightly worse than in previous companies. Unit Price within 2600-5800 rubles.

Connection options for the RCD to the single-phase mains with earth without

When mounting should follow the following guidelines:

• in the wiring diagram is not applicable grounding conductor;
• supply conductors should be connected only to the top terminals;
• neutral conductors should be connected only to the terminals having a marking N;
• electrical load current must comply with operating current;
• After installation, measure the insulation resistance of the entire power supply and test the device to work with the "Test" button.