Magnetic starters are switching devices that allow remote control of the load. In practice, they are most often used to start and stop induction motors. However, they can also be used to control other units, for example, pumping units, compressors, etc. If an experienced electrician can connect the starter without any problems, then the beginner will have to learn it.
Content
- The principle of operation and the device of the starter
-
Connection recommendations
- Device with a 220V coil to the mains
- With Stop and Start buttons
- Reversible circuit
The principle of operation and the device of the starter
The starters are installed in the mains supply, allowing power to be applied and disconnected. They can work with both direct and alternating current. For ease of use, they are often equipped with not only the "Start", "Stop" buttons, but also "Forward", "Back".
Starters are divided into 2 types according to the state of the contacts:
- with normally open - power is supplied to the mains only when the device is turned on;
- with normally closed - the load will be disconnected when the starter is activated.
The first type is most often used, since most units operate for a relatively short period of time. The main structural elements of the starters are the magnetic circuit and the coil. The first consists of two parts in the shape of the letter "Ш" and installed mirrored. In this case, the lower part of the part is stationary, and the middle one is the coil core.
The upper part of the magnetic circuit is movable, and terminals are installed on it, to which the controlled unit is connected. Fixed contacts are located on the body of the device and are required to connect the supply voltage.
In starters of the first type, the contacts are in an open state, thanks to the spring holding the upper part of the magnetic circuit. As a result, the supply voltage is not supplied to the network. After switching on the device, an electromagnetic field is generated in the coil. It is thanks to him that the upper part of the magnetic circuit is attracted to the lower one, and the contacts are closed.
Although contactors and starters are designed for similar tasks, there are differences between the two. The first type of devices:
- has powerful chambers for extinguishing an electric arc;
- has large dimensions and weight;
- used in electrical circuits with high amperage.
Connection recommendations
Often, to control the load, it is enough to use two buttons - "Stop" and "Start". Moreover, they can be located in separate buildings or in a single one. In the first case, connecting the contactor should not cause problems, since the device is equipped with only two contacts. One of them must be supplied with supply voltage, and from the second it leaves.
Device with a 220V coil to the mains
There are quite a few ways to connect these devices.. The easiest way is to connect the magnetic starter to a single-phase network. The supply voltage (220V) must be applied to connectors A1 and A2. They are located in the upper area of the device body. Power terminals L1-L3 are designed to supply any voltage that can be removed using terminals T1-T3.
For example, if L1 and L2 are connected to the battery, then the load is connected to terminals T1 and T2. This is not the most convenient way to connect, since the power supply can be connected to the load directly through a conventional breaker.
However, there are more interesting options that require additional devices, for example, a time relay. In such a situation, the phase should be connected to L1, and zero to A2.
With Stop and Start buttons
Contactors are often used to control motors. In this case, it is worth using the starter wiring diagram through the "Start" and "Stop" buttons. They must be connected to the phase line in series and connected to the A2 output. However, the load in such a situation will be in the working position until the "Start" button is pressed.
This is extremely inconvenient, and therefore it is necessary to introduce a self-picking circuit into the circuit. To implement it, you should use two additional terminals of the starter - NO 13, NO 14. They must be connected in parallel with the start button. As a result, the chain can only be broken with the Stop button. The supply voltage for all types of load is connected to any output L, and is removed from the T terminal located strictly below it.
Reversible circuit
If it is required to ensure rotation of the electric motor in both directions, it is necessary to use a reversible connection scheme. It can be realized with two identical devices connected in parallel. In such a situation, you can revert the phases on one of the starters. Most often, the difficulty in creating such a circuit arises with the signal chain.
The Stop button should be shared, and Forward and Reverse are connected to a separate starter. It is important to remember that each of the buttons must have its own self-locking chain.
So that the supply voltage is not supplied using two buttons at the same time, after the "Forward" button, connect the normally closed contacts of the second device. Conversely, if there are no normally closed contacts in the starters, a special attachment must be used.
