A part of any electrical circuit necessarily includes devices that open and close it. Until recently, the role of such devices in AC and DC networks was played by 3-position electrical switches. They were gradually replaced by circuit breakers. However, older devices are still in use today.
Content
- Main advantages
- Operating principle
- Varieties of devices
- Household use
Main advantages
The main advantages of this type of mechanism are its compact size and design versatility. These properties allow you to use switches successfully:
- in control and automation schemes;
- to control electric motors;
- to turn on and off the electrical network;
- for switching and de-energizing measuring circuits.
The demand for such devices forces manufacturers not to abandon their manufacture, on the contrary, to release new ones. improved models with wider functionality, mechanical and switching wear resistance. By improving the design, manufacturers have been able to reduce the size while increasing the number of connecting chains, fixed positions, and extend the life of the device to 10 years.
By its appearance, the 3-position pass-through switch resembles a conventional switch with one or two control buttons. But the mechanism of its action has fundamental differences. Unlike a switch, this device does not open the electrical circuit, but switches the lines. Looking at the kinematic diagram, you will notice that these two devices have a different number of lines.
Operating principle
A three-position switch, also called a cross switch, can control one light source from three locations. The crossover device has two input and two output contacts. Such a switching mechanism is mounted together with another similar device - a pass-through switch, which also has two output contacts, but only one input.
To close and open an electrical circuit, two devices must be located so that two conductors pass through them. In this case, when one switch is triggered, the electrical circuit is opened and closed on the other device. If one or more cross-switching devices are built into the circuit between them, this will allow you to regulate the operation of an electrical circuit from 3 different places by closing one line or opening both. The number of cross mechanisms must necessarily be odd, otherwise the system will always return to its initial position.
Depending on the position, the contacts of the device can be connected in different ways. When the device is not turned on, the first input remains connected to the first output, the second input - to the second output. When you press the button, a crossover occurs, the first input contact closes on the second output, the second input - on the first output. That is why the switch is called crossover.
A feature of such switching mechanisms is the absence of a fixed position of the keys, indicating the switching on or off of the device. Being in different positions, they can both open and close the network. The state of one device directly depends on the state of other switching devices included in a single circuit.
Varieties of devices
The design of the electrical switch can include multiple control keys. Depending on their number, the device is:
- one-key;
- two-key;
- three-key.
Devices with a large number of buttons are not available. This is due to the complexity of laying many live conductors. Devices with several keys control the supply of electricity to several consumers at the same time only if they are connected in parallel.
Special power switches can also be used in high-voltage power grids. They are most often used to control high power induction motors. The main function of such devices is to switch the winding from the "star" position to the "delta" position. The "triangle" corresponds to the normal mode of the electric motor, the "star" starts its operation.
Galet switches are considered a separate type. The metal ring in them is connected with the axis of the device. Contacts in the amount of 12 pieces are located after 30 degrees. Thus, when the axis is rotated by 330 degrees, the common output is switched with eleven different electrical circuits connected to the contacts. Some models of biscuit devices have a split ring, which allows synchronous connection with five circuits.
Most swivel mechanisms are assembled by soldering. The exception is tumbler devices, which are fastened with screws. With any installation method, the correct position of the outer casing and the inside of the instrument must be maintained. This position can be achieved using only those fasteners that meet the technical standards of a particular switch.
The design features of different models affect the way they are installed. When installing the devices, pay attention to the following points:
- Wiring type (open, hidden).
- Connection diagram (single-pole, single-pole double or double-pole for two positions).
- A variety of control buttons (regular, sticky, double).
Regardless of the type, the installation of the switching device must be carried out in compliance with safety measures. Before installation, it is imperative to de-energize the electrical network, then proceed in strict accordance with the instructions.
Household use
Electrical switches with three positions for domestic use are rarely used. At home they can be used as switches and switches for chandeliers, lamps and other lighting devices.
If you install two such devices at the beginning and at the end of a long corridor that resembles a gallery, this will greatly simplify the process of controlling the lighting in it. In standard sized rooms, there is no particular need to install these kind of switches.
