Principle of operation
3-position switch
The 3-position switch has a handle with three positions for opening and closing the circuit. The middle position ensures the opening of each existing group of contacts. The user controls the device manually. The upper contacts are usually used to connect inputs, and the lower ones - loads. Such a device is not equipped with releases (thermal or electromagnetic), so when installing it, automatic switches are installed at the inputs that are triggered when overloaded. This configuration will prevent sparking incidents and damage to the integrity of the wiring insulation material. In the past, these devices were used as master input devices in switchboards. Over time, this place was taken by automatic switches, but the flexibility and simplicity of the design of position switches, as well as their low price, ensure that these products are quite popular.
Re- or breaker
Difference between a pass-through switch and a switch
To make the final choice, you should develop an initial wiring plan or study an existing one. It is usually attached to the technical documentation of the apartment or building. Then you need to determine the longest sections or rooms (workshops, corridors), imagine possible situations based on personal preferences (such as in the bedroom).
If you need to control one light source from different sides, you should install a switch. Then select the type of device - pass-through and cross-over switch. The first allows you to turn off the lamp from two different points, the second - from three or more. To install the latter type and route the wires correctly, it is better to invite a professional electrician.
Can a switch be used as a switch
During use, different situations arise. For example, after purchasing an apartment, it turned out that the previous owners installed switches in several rooms, and now their functioning is no longer needed.
To redirect the action of the device, it is enough not to use the third contact, which diverts the flow of electricity in another direction. First of all, the complete circuit of the electrical network closed by this switch is determined. The non-essential contacts are then isolated. After this, the mechanism will stop redirecting the current and will begin to work like a regular switch.
Types of three-position switches
3 Position Stack Switch
Electrical 3 position switches are available in a variety of designs. Some models are equipped with the option of fixing the switch position. They are equipped with a key locking mechanism that prevents spontaneous transition to another position. Others that do not have this function return to their original position on their own. The design of some devices provides for a zero position - it involves disconnecting all contacts.
Typically, products are manufactured with the expectation of operation in electrical networks with a nominal current of 25, 16 or 10 A. As for voltage, for direct current its value can reach 220 V, for alternating current - up to 500. The devices are equipped with markings indicating the power level and protection category.
The most common design option is a 3-position mechanical packet switch. Their control element is not a button, but a handle. Modern models are equipped with ergonomic handles, the design of which prevents fingers from slipping. There are two types of products - biscuits and cams.
The biscuit switch device includes plastic plates (bags) with contact pins rigidly fixed to them. Between the latter there are fiber washers for extinguishing sparks, which, together with a double break in the electric arc, make it possible to switch high currents. There is also a moving contact connected to the switching mechanism. Its position is set by turning the shaft, which is provided by a handle and a special spring, which allows you to instantly open and close the contacts. The shaft has 3 set positions, each of which corresponds to a certain configuration of clamped or open pairs of contacts. Such a device can be used, among other things, to connect a three-phase electric motor with a reverse option - rotation of the rotor in a direction other than normal.
Operation of automatic three-phase switch
The cam device also includes a series of packages, but arranged differently. On the outer sides of the plates connecting to the body there are moving contacts, and on the inner sides there are static ones. The first of them look like bridges with springs. Their position is regulated by a rod mechanism that changes position under the action of a cam. The latter, in turn, changes its position through the handle and shaft. Both in the case of biscuit models, and in devices with cams, the shaft can have a different number of positions (up to eight). In three-position devices their number is three.
The switch can be mounted on a DIN rail, on a wall, or in a cabinet, depending on the model. Explosion-proof products are produced for use in industries that pose a danger to human health. Most three-position switches, however, are susceptible to explosions, temperature changes, and do not tolerate moisture. The degree of sensitivity of the device to environmental conditions can be determined by its appearance: if the product is open and lacks a protective casing, it is highly sensitive; it should only be installed inside a switchboard in a room with dry air. Switches with a plastic or metal housing and contact-protected clamps can also be installed outside the switchboard.
If the housing is hermetically sealed, the device can be installed even outdoors. During operation, mild mechanical impacts and vibration are allowed (no more than 35 Hz).
The advantages of the devices include reliable operation, resistance to wear and tear, and a fairly low price. They suppress electrical arcs very quickly, but can withstand a limited number of switching overloads. A weakness of these products compared to circuit breakers is also their limited capabilities as a protective device: they do not protect against short-circuit incidents. Also, mechanical switches cannot be repaired: if the product becomes unusable, it is dismantled and subsequently disposed of, and a new one is installed in its place. They fail relatively quickly, although some manufacturers claim that the device can withstand up to half a million switchings.
Household use
Three-position switch EKF Basic
There are many options for using three-position switches for 220V in industry and everyday life:
- control of light and transformer substations;
- switching programs for the operation of electric welding, heating and other production equipment;
- manipulations with electric motor modes;
- remote control of asynchronous electric motors;
- automatic entry of reserve;
- switching in panel devices.
These products are also used for power supply to substations, for example, in grounding structures and switching measuring instruments.
Multi-position switches of modular type
The cam burst switch is the most common type of these devices, like other switches, it is used to control various types of electrical loads.
Cam switches
The scope of application of cam switches is quite extensive; here are some examples of their use:
- AC and DC control switchboards;
- emergency shutdown systems, automatic transfer of reserve, switching of operating modes of electric motors;
- control of transformer substations and lighting;
- equipment for substations (control of grounding switches, sectional switches, disconnectors, etc.);
- switching heating equipment modes (turning on, off, switching electric heating elements of the load);
- selection of operating mode of electric welding equipment, etc.
Cam switches consist of several packages (each responsible for switching one line) placed in one housing. The figure below shows the structure of such a package.
Cam Switch Package
Designations in the figure:
- a - fixed contacts (4 pcs.), to which wires are connected;
- b – a special protrusion “cam”, which allows you to hold and move the rod;
- c – group of movable contacts (there are two of them in this type);
- d – two guide grooves (allow the rod to make translational movements);
- e – two rods covered with an insulating shell;
- f – contacts (8 pcs.), usually made of an alloy containing silver;
- g – package;
- h – two threaded rods (fix the bag and the lid);
- I – rotor;
- J – four springs (return the rod to the closed position);
- k - shaft connecting the handle to the rotor;
- l – four screws for clamping cable wires.
Note that the batch switch (cam switch) can have several positions, including zero, that is, when the contacts are disconnected. The figure shows the state of the switch in the neutral position.
Schematic representation of the switch in the zero position
ABB switch in zero position mode
Note that all the main characteristics of the switches are indicated on the device case; the following are displayed there:
- switch type;
- rated current for which the switch is designed;
- switching diagram and table;
- protection class.
Below is a diagram and switching table shown on the housing of the SPAMEL rotation direction switch.
Scheme and switching table of the SPAMEL switch
Thanks to this table, you can clearly see in what position and which groups of contacts are connected.
How to connect
In Soviet times, the use of a three-position switch for power supply to apartment buildings was common and ubiquitous. Then they were installed in distribution boards. Nowadays, instead of such devices, automatic ones are more often used. If the owner prefers to use a three-position three-phase switch, it can be installed in front of the electricity meter leading to the switchboard so that the apartment network can be turned off completely if the need arises. Also, to enhance network protection from excess load or short-circuit incident, we can recommend the combined use of both devices.
When installing the device in a private house with modest electricity consumption, as well as in a country house, a single-phase circuit can be used, connecting the device to the home electrical network of a backup source. Indicator lamps should be placed inside the panel to indicate that the network or generator is turned on.
Connection diagram
Typical connection diagrams
When purchasing cables for mounting a three-position device, it is necessary to take into account the maximum operating current values in the electrical circuit. If the diameter of the conductors exceeds 6 mm2, special tips are purchased for them. Less thick wires can be connected directly to the device using soldering or ring cutting.
Typical diagrams suitable for a particular device, including a diagram for connecting a switch from three different places, are given in the technical documentation accompanying it. Some of the three-position products can be connected not only to 3 poles, but also to 1, 2 or 4 (the possible number of poles is indicated in the device passport). At the entrance to the apartment, the device is placed at the point of tapping from the common phase conductor and zero in order to separate the apartment line from the main line. Installation of the switch and its subsequent adjustment can only be done when the electricity is turned off. Modern products designed for use in residential panels usually require installation on a 35 mm DIN rail. Their terminal clamps are marked with numbers, which avoids confusion during the installation process. After installation, the device, as well as adjacent contact connections, must be cleaned with a dry cloth at least once every 6 months, having first disconnected the power from the network.
As a home network switching device, manual position switches are often considered an obsolete device. However, the ease of management and installation, as well as the price, provide them with some popularity to this day.
Construction portal No. 1
Modular three-position switch MP-63 4P 63A TDM*
· The terminals of the device are marked, which allows you to avoid errors during installation.
· MP-63 switches can be installed in any position without changing their nominal characteristics.
· The supply line can be supplied both through the upper and lower terminals, without disrupting operation.
· Detailed installation and operating instructions make it easy to install the machine even for a novice installer.
· Carrying current in normal mode.
· Switching electrical circuits.
· Prompt switching on and off of electrical circuits.
· Input, sectional panels of input-distribution devices.
· Switchboards for switching to backup power.
· Control panels for generating sets.
Rated current - the current value in amperes (A) that the switch is capable of passing indefinitely and remaining in working condition
· Rated voltage – AC voltage (sign
), at which the machine operates under normal conditions.
· Number of poles 1, 2, 3,4
· The housing and parts of the device are made of flame retardant plastic.
· The marking of the device is made in accordance with GOST rules and is not subject to erasure.
· Three fixed positions of the handle I-0-II.
· The middle position of the handle fixes the zero position of the contacts.
· The device uses an ergonomic control handle that prevents fingers from slipping.
· Packaging made of hard varnished cardboard prevents damage to the goods during transportation and beautifully highlights the products at the point of sale.
Advantages
The terminals are marked, which helps to avoid installation errors.
The universal head of the reinforced terminal clamp screw allows the use of both a Phillips and slotted screwdriver. This provides the necessary tightening force.
The supply line and load can be supplied both through the upper and lower contacts of the MP-63 modular switches, without disrupting operation.
Group packaging made of hard varnished cardboard prevents damage to the goods during transportation and beautifully highlights the products at the point of sale.
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