Bipolar and three-pole switches: purpose, characteristics, installation features

The purpose of circuit breakers, which are implemented in electrical networks, relates to protective functions. If you use a handheld device in network congestion mode, the likelihood of significant damage to equipment increases significantly.

Automatic two-pole and three-pole circuit breakers reduce such risks to a minimum, as they provide instant open circuits in case of an accident.

We will understand the features of electric machines, give tips on the selection, installation and operation of such devices.

Design of circuit breakers

In the practice of using such equipment, three types of devices are often used: single-pole, two-pole, three-pole.

What is the difference between these three types of machines? Let's try to figure it out.

The community of these electrical appliances is more than diverse. Assortment is not to capture. However, the high number of protective devices is fully justified, so they have to be used in a variety of schemes

A single-pole device, in general, does not cause special problems. If you introduce single phase circuit breaker, then the device will work like a normal switch, only in the automatic reaction mode - that is, without user intervention, it will break the circuit in case of violation of the specified operating conditions.

Brief description of the bipolar

A similar device, but executed in the form of a two-pole circuit breaker, is slightly different in functionality.

The circuitry of a two-pole device is made taking into account the control and comparison of the working conditions of two independent current lines.

The bipolar design of the circuit breaker is designed to protect and block two different lines of the same electrical circuit. Such devices, along with phase locking, are also used to break the neutral conductor circuit.

Bipolar automatic machines are used, as a rule, for implementation in projects of building electric networks, when it is necessary to monitor and compare the working conditions of two sections of a single electric network. In fact, the bipolar configuration of the device is a tandem of a pair of unipolar devices.

However, the two-terminal protection and blocking circuit works on the principle of comparing the parameters of each device individually, in real time. If the parameters go beyond the boundaries of the installations in either of the two control sections, both lines are instantly broken.

This important point shows: the replacement of a two-pole circuit breaker with a pair of ordinary single-pole devices is impossible in principle. In case of overload of one of the circuits (or short circuit), only one machine will work.

Execution of a two-terminal device: 1 - the case from plastic of good quality; 2 - operation from -25 to + 60ºС is allowed; 3 - mounting on a DIN rail; 4 - operational platoon mechanism; 5 - operation indication; 6 - information panel; 7 - technical designations (+)

But given that the electric network is single, electricity will continue to flow through a second device that feeds another section. This situation leads to grave consequences.

Meanwhile, there are two subspecies of bipolar devices:

• with protection of one pole and normal neutral switching;
• with protection of both poles and their simultaneous switching.

The former are usually used as input machines, thanks to which the phase and neutral conductors are switched. At the same time, such a switching circuit provides for the use of an additional PE line - a grounding wire.

This device also looks constructively like a two-terminal device. However, in fact, the device is a single-pole circuit breaker with support for the function of blocking (switching) the neutral line of the electrical network

The second find application in the circuits of the same network, where two sections are fed, operating under different current loads.

Features of a three-terminal device

The main purpose of a three-pole circuit breaker is the use of three-phase networks in circuits. Design features of this type of devices are the presence of protective functions at each individual pole.

The operation of protection at any of the poles leads to the opening of all poles.

Design for working with a three-phase network. Circuit breaker for three independent poles with a common interlock. As can be seen in the device diagram, protection is carried out due to the action of bimetallic plates, as well as electromagnetic trip units (+)

Despite the specific purpose of machines of this type, it is quite acceptable to use them on single-phase or two-phase lines.

Structurally, a three-pole machine contains the following elements:

• management mechanism;
• contact system;
• arc extinction module;
• trip device.

Loose contacts are usually mounted inside the instrument cover. The contact system communicates with the traverse of the main contacts in a kinematic way.

Functional components of the device are mounted inside the housing. The cover and body of the machine are made of materials that do not allow electric current (plastic, textolite, etc.).

The inner contents of the classical structures of three-terminal devices: 1, 6 - the chamber of extinction of the electric arc; 2, 6 - release of electromagnetic action (coil with a core); 3.4 - thermal release (bimetal plate) (+)

The three-terminal protection mechanism provides momentary shutdown, both in the “auto” mode and in the case of manual operation. In this case, if there is an overload in the electrical circuit, a momentary shutdown occurs regardless of the force exerted on the control handle.

That is, even if the user keeps the handle in the on state, the machine will still open all poles in overload mode.

There are modifications to the three-terminal network, where another pole is added under the neutral conductor. In fact, we are talking about a four-pole design in terms of structural details.

Modified device with three phase poles with an additional zero pole. Often this type of automaton is called a four-terminal device, which in principle is quite true from a structural point of view

Functionally, the four-pole machine resembles a two-pole system. The task of the device is the same, only with respect to a three-phase network.

Generalized technical characteristics of machines

Information on the main parameters of circuit breakers is indicated on its case. To understand alphanumeric characters, you must be able to “Read” device labeling.

Widespread in everyday life and industry are devices that meet the following main technical characteristics, depending on their design:

Devices are selected according to certain criteria, among which voltage, value of rated current, temperature indicators.

Read more about choosing circuit breakers in the articles:

1. Choosing a circuit breaker: types and characteristics of automatic machines
2. Machine selection by load power, cable cross-section and current: principles and formulas for calculations

Mounting subtleties of switches

For all electrical appliances of this design, the procedure for introducing into the electrical circuit is determined.

Installation of circuit breakers - at first glance, the procedure is technically simple. However, taking into account exactly all existing installation rules, the installation process of machines can be compared with the work of creating computer software

In accordance with the established procedure, in particular, the following actions of the installers are expected before the bipolar and three-pole switches are installed:

• the device must comply with the design for the current circuit;
• the machine case has no deformation and damage;
• the on / off lever clearly works in manual activation mode.

The base on which the device is supposed to be installed must be checked for evenness. Installation on the base is not allowed, where due to the uneven surface after fastening, the machine body is subjected to bending stresses.

Connection to network conductors

Connection of copper conductors having a cross section of 16 - 25 mm²perform through cable lugs (GOST 9688-82). If it is necessary to make a connection with conductors of copper with a cross section of 4 - 16 mm²other types of cable lugs are used (GOST 7386-80).

With regard to the connections of aluminum wires, end elements are used by analogy with TAM-7, corresponding to the parameters GOST 9581-80.

Tips of conductors supplied to the terminals of automatic machines. Often this moment is ignored, the conductors simply twist and in this state are connected to the device. In fact, this approach is already considered a violation. The exception is wires with a cross section of less than 4 mm

Network conductors supplying voltage from a power source are connected to the upper group of fixed contacts of circuit breakers. Conduct and connect the conductors so that they do not create forces on the terminals of the machine.

Tips should be tightened with contact clamps tightly, but without critical efforts that could lead to thread breakage.Sealing conductors in cable lugs should be given high attention. Be sure to use insulating tubes, tape as a protective sheath.

Nuances of arrangement and fixture

When you perform the installation of several pieces of equipment, you must follow the rules for the arrangement of devices relative to each other. So, the distance between closely spaced devices should be maintained at least 5 mm.

Installing switches in a group. It looks quite nice and neat. Meanwhile, in this case, the installation process is performed with errors. According to the regulations, when mounting in a group, the distance between the walls of adjacent devices should be at least 5 mm

Minimum distances from the metal parts of the switchgear: from top 30 to 50 mm, from the side 5 to 10 mm, depending on the magnitude of the supplied voltage.

If instruments used are used that are structurally made in an additional shell, all mounting manipulations are performed with the shell cover removed. The installation of the cover is carried out taking into account the correct entry of the drive mechanism leash. Screw fastening of the cover is performed evenly.

Upon completion of installation, the machines must be checked for clarity of the on / off moment.

Circuit diagrams and circuit breaker connection rules are described in detail in this article.

Maintenance during operation

The normal operating conditions of bipolar and three-pole circuit breakers allow you to allocate time for technical inspection of devices no more than one prophylaxis in three years of operation. This fact once again confirms the high quality of performance of almost any automatic machines.

Instrument Maintenance This procedure involves testing the integrity of devices and the reliability of contact groups. As part of the maintenance, the devices and their locations are cleaned. Checks the quality of the automatic mechanisms

Meanwhile, according to the instructions, a technical inspection is necessarily carried out if the circuit breaker is tripped due to a short circuit current.

For any reason, whether the device is triggered in an emergency or scheduled maintenance, the technical inspection of the devices includes:

• diagnosing the on / off mechanism in manual mode without load;
• checking the tightness of the screws of the main and loose contacts;
• reliability of fixture of the device to the basis;
• cleaning from dirt and foreign objects;
• simulation of shutdown by the method of mechanical action on a sensitive element;
• performance check in operating mode.

The practice of using electric networks notes the handling of devices from different manufacturers, including domestic and foreign ones.

Most of the automatic protection devices in use are characterized by excellent quality performance.

Conclusions and useful video on the topic

What are machines and how they differ, you can find out from the following video:

About the selection criteria for protective devices:

The reliability of the automatic locking devices is often determined not by the brand, but by the correct selection taking into account the workload. Also, an accurate calculation of the cross section of conductors supplying the load from the machine and the calculation of the cross section of the input cable have a significant effect on the operation of the devices.

When all the nuances of installation are taken into account, even Chinese devices, which are several times cheaper than branded ones, work for a rather long period of time without any complaints.

Share with your readers your experience in connecting bipolar and tripolar switches. Please leave comments, ask questions about the topic of the article and participate in discussions - the feedback form is located below.