Modern manufacturing processes use the rotational energy of electric motors. These machines have high reliability, durability and other advantages, but, unfortunately, they are not without drawbacks; the most important of which is the high starting current. Simply put, the load at the moment of starting increases many times and this circumstance does not allow the use of standard switches.
To solve this problem, special devices have been developed - electromagnetic starters or contactors.
Device
In fact, the starter is an electromagnetic relay designed to switch a three-phase load (electric motor, heating element, etc.). An electromagnet is located in a housing made of heat-resistant plastic or PCB. The core is split into two parts.
One part is stationary, a coil is located on it (see. (see gallery below).
The second part is connected with a mobile contact group. The contact group includes main contacts designed for high current and additional contacts for control circuits. Contacts, in turn, are divided into fixed and movable (see gallery below).
How does a magnetic starter work?
To operate the starter, a voltage is applied to the coil, the value of which depends on the needs of the electrical installation (in most cases, 230 or 400V). In the stationary part of the core, a magnetic field is formed and attracts the moving part.
Moving contacts are pressed against fixed ones and form "bridges" for the flow of electric current. This process occurs quickly and abruptly, in connection with which high-quality switching and retention of a large starting current is ensured. To extinguish the electric arc at the moment of closing the contacts, the body provides arcing devices made of metal or textolite plates.
Additional contact groups go into a closed or open state, depending on the control scheme.
The main parameters when choosing a starter are the rated current, the voltage of the electromagnet coil. As a rule, the current parameters are selected with a margin of 10 -15% to the rated current of the electric motor.
Currently, many models and varieties of electromagnetic starters are produced. Products of European manufacturers are considered to be of high quality and reliable, Chinese products and domestic ones are of a lower class. Soviet electricians are very popular among practicing electricians, the quality and reliability of which are not inferior to world brands.