In this article, you will learn what magneticstarters, connection schemes consider them, and most importantly - maintenance of 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 purposes they are intended for.
Designation of starters
Connection scheme for single-phase magneticThe 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 able to turn the consumer on or off from an alternating current network.
But here reversible MP can not onlyabove-mentioned doing. 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. Management MP is carried out using the buttons:
- "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
Magnetic starter, whose connection schemeis 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 on the street is allowed, but only on condition that it does not receive sunlight and rain.
Design of magnetic starters
There is any magnetic starter 220V, circuitthe connection 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, there are still a lot of trifles, for example traverse, sliding along the guiding axes. It is anchored. In addition, interlocking 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 MP's work lies 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 wiring diagram can only differ (depending on the presence of the 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 begins to work. But when the coil's power is turned off, the electromagnet stops working. Reverse 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 it looksmagnetic starter, connection scheme "reverse" if used. In fact, these are two identical devices, combined in one package. With the same success as it was said before, simple MPs can be used if one knows the scheme of inclusion. In the starters there is a blockage, 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 an electrical protection degree is provided. 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 this, the engine can be turned on in the opposite direction. Please note that the starter's power must be twice as high as that of the motor, if an opposi- tion or braking is used.
And now consider a typical magnetic starter380V. The connection scheme is not complete 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.
Thermal relay, installed on magneticstarters, allows you to make small adjustments. The so-called set point 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, it is enough to just set the arrow on the plastic disc opposite the corresponding label with the value of the current limit of consumption. Please note that thermal relays are not able to carry out short circuit protection. Use automatic circuit breakers for this purpose.
How starters are mounted
It is worth noting that the connection scheme of the magneticthe PML starter 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 more simply, then on the wall of the electrical panel. If there is a thermal relay in the design, then it is necessary that the temperature difference between the MP and the electric motor is minimal.
To avoid false triggering of the starter orits protection is unacceptable to carry out the installation of the device in places that are prone to shocks, shaking, vibrations, jolts. 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 the contact and in order that the spring washers of the clamps do not bend, the wires must be bent in the form of a circle or the letter "P".
Switching on the starter
Try to always follow the techniquenever work without turning 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 - carry out visual inspection for the presence of cracks, distortions, phase closures. Remember to disconnect the entire drive circuit from the power supply. Try to press the traverse by hand, it must move freely along the guides. Check the system carefully for all magnetic starters, wiring diagrams for power conductors.
Pay attention to the coil connectionelectromagnet of the starter. Also check that it is within the allowed value. If you need 24 V, then so much and serve. Check up all control wires, whether they are correctly connected to the buttons "Start", "Stop", "Reverse" (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
Вот и все, рассмотрены полностью магнитные starters, connection schemes, it remains to mention the care of them. During operation, the status of the magnetic starter must be constantly monitored. The main care work 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 (not wet). 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, then 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.