To understand how to connect a magnetic starter, you should understand the principle of its operation. It is simple and completely identical to the one on which any relay works.
The main task of the magnetic starter is the remote connection of a powerful load, which can be done both in manual mode and during the algorithmic operation of an industrial automated installation.
The main components of a magnetic starter are an inductive coil that creates a magnetic field, an armature mechanically connected to one of the contact groups, and another pair of contacts.
The inductor is included in the control circuit, consisting of sequentially connected buttons "Stop" with normally closed contacts and "Start" with normally open contacts. Parallel to the "Start" button, another contact pair is switched on, which closes simultaneously with the connection of the load.
The magnetic starter works as follows: when you press "Start", the electrical circuit closes, the current passes through the closed contacts of this button and the "Stop" button (because they are normally closed), which means - until they pressthis button, the circuit will not open. When an electric current passes through the coil, a magnetic field arises in it, which attracts the armature, which, in turn, connects the contacts - there are four pairs of them in total. Three of them are basic and are designed to turn on a three-phase payload, such as a powerful electric motor. The fourth pair is connected in parallel with the start button, which can then be released, and the current in the circuit will pass through these contacts.
In order to disconnect the load, just open the solenoid circuit. For this, the Stop button is intended, the contact group of which is closed in the normal position, and opens when pressed. Now everything happens in the reverse order: the circuit is interrupted, the magnetic field of the coil disappears, all contacts are opened - both power and holding. The "Stop" button can be released - the current will no longer flow through the control circuit, because the contacts of the "Start" button are open in the unpressed position. Everything, the magnetic starter is off.
As a rule, the magnetic starter coil is designed for a voltage of 220 volts alternating current with a frequency of 50-60 hertz. Devices that use magnetic coils or transformers designed exclusively for a frequency of 60 Hertz are better not to be used here - they can fail, but a domestic or European magnetic starter can be used in America without restrictions.
Typical installation error - turning on the control circuit is not betweenneutral and phase, but between phases. In this case, the coil gets 380 volts instead of 220, and it burns out.
With all the simplicity of the device, the design of the magnetic starter is constantly being improved. Design bureaus creating new switching devices strive to reduce the noise during operation and to reduce the electric arc formed at the moment of connecting or disconnecting contacts. This is especially true for high-voltage starters, designed to work with a voltage of a thousand volts. Thus, the Swiss-Swedish joint venture Asea Brown Boveri Ltd has been producing switching equipment for electrical circuits since the late nineteenth century, and has accumulated vast experience in the production of this equipment. The ABB magnetic starter is what Rolls-Royce is to cars.
