Magnetic starters. Connection diagrams of magnetic starters

In this article you will learn what magnetic starters are, consider their wiring diagrams, and most importantly - care for devices. To date, electric motors with a short-circuit rotor have been widely used in industry (their share is approximately 95-96%). They work in a duet with magnetic starters. In addition, starters expand the capabilities of the electric drive. But about everything in order, first you need to answer the question about what purpose they are intended for.

Designation of starters

The connection scheme of a single-phase magnetic starter allows switching any user. Of course, if his food is also produced from one phase. And to be more precise, the MP allows remote control of an electric drive or other device. For example, a non-reversing starter is only capable of making the consumer turn on or off from the AC mains.

But here reversible MP can not only do the above. They are able to change the phase connection to the motor. And this means that the rotor will start to rotate in the opposite direction. MP control is carried out using the buttons:

• "Start";
• "Stop";
• "Reverse" (if necessary).

And these buttons have a supply voltage of not more than 24 volts. All control is carried out with the help of low voltage. And to power the coil of an electromagnet more is not required.

Types of magnetic starters

The magnetic starter, the connection diagram of which is given in the article, can be made in three versions. Everything depends on the conditions under which it operates. So, open execution of starters is intended for installation in electric boards. Fastening is made on DIN-рейку. It goes without saying that the electrical board must be protected from foreign objects such as dust or liquid.

The second type of housing is protected. Although it is intended for indoor installation, not shields, it is still unacceptable to get a lot of dust on it, much less fluids. If it is necessary to install magnetic starters, the connection schemes of which are given in the article, in conditions of high humidity, it is more reasonable to use dust-proof ones. True, they have a restriction - installation in the street is allowed, but only on condition that it does not receive sunlight and rain.

Design of magnetic starters

It consists of any magnetic starter 220V, the connection scheme of which is shown, from one main part - the magnetic system. It is a coil wrapped around a metal core, and a movable armature. All this is in a plastic case. But this is the basis, still there are many trifles, for example the traverse, sliding along the guiding axes. It is anchored. In addition, the interlock and main contacts are connected to it. They are equipped with springs, which help to open when the power supply of the electromagnet is disconnected.

How the starter works

At the heart of the work of the MP is elementary physics. When applying voltage to the winding, a magnetic field arises around the core. As a result, the movable armature begins to be attracted to the core. So any magnetic starter works, the connection scheme can only differ (depending on the presence of a reverse). Incidentally, reversible movement can be achieved with the help of two conventional MPs. The starter contacts are normally open by default.

When the anchor moves to the core, they close. But there is another design, in which by default the contact group is normally open. In this case the picture is the opposite. Consequently, when the voltage is applied to the coil, the circuit closes and the electric drive starts working. But when the coil's power is cut off, the electromagnet stops working. The return springs are activated, which cause the contact group to move to its original position.

Starter startup circuitry

To begin with, it is worth considering how the magnetic starter looks like, the "reverse" connection scheme, if used. In fact, these are two identical devices, combined in one housing. With the same success as it was said before, simple MPs can be used if one knows the scheme of inclusion. The starter has a lock, which is carried out by means of normally closed contacts. The fact is that it is unacceptable that they both join at one time. Otherwise, the phases will close.

There is also a mechanical protection, installed in the case of the starter. But it can not be used if there is an electrical degree of protection. The peculiarity of the reverse is that it is necessary to completely disconnect the drive from the power supply. To do this, the motor is disconnected from the mains first. After this, it is necessary that the rotor completely stop rotation. And only after that the engine can be turned in the opposite direction. Please note that the starter's power should be twice as high as that of the motor, if an opposi- tion or braking is used.

Thermal relay

And now consider a typical magnetic starter 380B. Connection scheme it can not do without additional protection. And such is the thermal relay, which is installed on the case of the starter. The main task of the thermal relay is to prevent thermal overloads of the motor. They, of course, will be present, but insignificant, the electric motor overheating is impossible. As a measure of thermal overload, a bimetallic plate protrudes . Protection, however, is analogous to the design of the circuit breaker.

The thermal relay, installed on magnetic starters, allows for small adjustments. The so-called setting is the setting of the maximum value of the current consumed by the motor. Typically, this setting is done with a screwdriver. The engine has a groove for it, and also a graduation. The procedure is simple, just set the arrow on the plastic disc opposite the corresponding label with the current consumption limit value. Please note that thermal relays are not capable of short-circuit protection. Use automatic circuit breakers for this purpose .

How the starters are mounted

It is worth noting that the connection scheme of the magnetic starter PML allows the possibility of their installation inside the electrical panels. But there are requirements for all designs of starters. To ensure high reliability of operation, it is necessary that the installation is performed only on a perfectly flat and rigid surface. And it should be vertically located. If to put it simply, then on the wall of the electrical panel. If there is a thermal relay in the structure, it is necessary that the temperature difference between the MP and the electric motor is minimal.

To avoid false triggering of the starter or its protection it is unacceptable to mount the device in places that are prone to shock, shaking, vibration, jolting. Including installation on one panel with electric starters, which have a current of more than 150 Amperes, is forbidden. When such devices are switched on and off, a sharp impact occurs. Wiring must also be done correctly. In order to improve contact and in order that the spring washers of the clips do not bend, the wires must be bent in the form of a circle or the letter "P".

Switching on the starter

Always try to follow the electrical safety rules, never work without switching off the power. If you have little experience, then at hand there should always be a scheme. Photo of the magnetic starter connection is given in this article, please see. What should I do before starting the starter? Most importantly - conduct a visual inspection for cracks, distortions, phase closures. Remember, you need to disconnect the entire drive circuit from the power supply. Try to press the traverse by hand, it should move freely along the guides. Check the system carefully for all magnetic starters, wiring diagrams for power conductors.

Pay attention to the connection of the starter solenoid coil. Also check that it is within the allowed value. If you need 24 V, then give so much. Check all control wires to see if they are correctly connected to the Start, Stop, Reverse buttons (if necessary). Is there a grease solution on the contacts? If not, apply it, otherwise the lock may not work in a timely manner. After this, it is possible to start the circuit and start the drive. Note that the coil of an electric magnet may humble slightly in this state.

How to care for starters

That's all, we considered fully magnetic starters, wiring diagrams, it remains to mention the care for them. During operation, it is necessary to constantly monitor the status of the magnetic starter. The main work on care is to prevent the formation of a layer of dust, much less dirt, on the surface of the starter or thermal relay. From time to time, the contacts must be tightened to connect to the mains and to the drive. Dust must be removed with a cloth or compressed air (only not damp). Do not clean the contacts, as this affects the resource of the device. If necessary, a replacement is made. The service life depends on many factors, but the most important is the operating mode. If the starter is constantly on the move, making commutation, it will not last long. Its life is measured in the number of cycles of switching on and off, and in not in hours or years.