Valuable methals in the contacts
Contacts, or contactors is a two-position, electromagnetic device. The meaning of the word in English is “contactee, contact“. This device is designed to turn on / off the circuit running in normal operation. The contact is also a kind of relay, working on electromagnets. Nowadays, all the couplers with a large current load are working with a help of contacs.
The most common contacts are with one or two poles containing a significant amount of silve. They are used for direct current. Three-pole contacts are used with a variable current.
There are high demands to the contacts: they must have considerable mechanical, electrical stability, because the switching-on / shutting off frequency can vary from forty to three thousand times per hour. Contacts containing a significant amount of silver are found everywhere, where there are switching and electrical devices.
Silver-containing Contact can be:
- Electromagnetic;
- Pneumatic;
- Hydraulic.
The electromagnetic contact consists of the following elements:
- Electromagnetic system;
- Contact main power;
- Main contact block;
- Device for electric arc discharge;
- Retractor coil.
Characteristics of contacts containing silver
Contacts are characterized by the following parameters:
- The type of electric current passing through the main control circuit;
- By the number of poles;
- According to the nominal current flowing through the main circuit;
- According to the rated voltage of the main circuit;
- On the nominal voltage of the coil “Turn on”;
- By the presence, absence of auxiliary contact;
- On a type of assembling;
- By the type of connection of the conductors of the management chain, the main chain;
- By the type of connection;
- By the presence / absence of external conductors.
The principle of contacts’ work
The main consistuent elements of contacts are a coil and wires. The coil consists of a core, mechanically connected to the electrical contacts “on / off”. The a-contact (switching) closes the circuit through which the electric current “flows”. The break contact (contact breaking switching-off) stops the current supply, breaking the circuit. The frame helps to provide the coil with strength and durability, cools all elements of the contactor. Usually, it is produced from copper or steel.
The principle of opposite operation is put into work of the device. When voltage is applied to the electromagnetic coil, the core moves upwards under the action of the magnetic field, closing the circuit. This action allows the access to the equipment and electric motors, the device starts to work. The equipment is disconnected after the power supply is cut off and the circuit is opened. Contacts are disconnected or switched on by means of a special device, with the Stop / Start buttons.
