Connection diagram of magnetic starter: step by step guide

A person unfamiliar with electrical engineering may think that electrical appliances and equipment to manage their work are incredibly complex. In fact, this is not quite so, and at the heart of almost all powerful systems is an electromagnetic contactor or a starter. Without such solutions, only completely electronic devices are dispensed. Knowing how the connection scheme of the magnetic starter is implemented , you can not only make repairs yourself, but also perform simple installation.

The main element of the ballast (ballasts)

The magnetic starter is an electromechanical device intended for direct switching of circuits with voltage up to 1 kV. There are several contact pairs on it, through which the lines are switched and the distribution of electrical energy. Sometimes a thermal relay that implements the protection function of the connected equipment is included in the design of the starter. Depending on the design, open and closed contactors are distinguished. A striking example of the first - the famous "frogs" or "frogs", in which to access the internal elements it is enough to take out the fixing pin (class PAE). The second - it's almost all the rest (PML, PMA), installed inside the dust-proof housings.

Remembering electrical engineering

Before we consider how to connect a magnetic starter, it is worth remembering the course of physics in high school. As we know, when a current flows through a conductor around it, a special kind of matter appears-a magnetic field that has an attractive effect on most metals. If you take a thin conductor and wind it on a metal core, then due to the magnetization of the latter, the resultant field is greatly enhanced. It is this principle that is the basis of the starter's work.

Design

Structurally, the magnetic starter is a product whose "heart" is a coil consisting of a magnetic circuit (a P- or S-shaped base of sheet steel of high electrical resistance) and a thin lacquered wire wound on it. The second part is physically a continuation of the first, but is separated from it, being mobile. Before the current is applied to the coil, there is space between the ends of both parts, which is provided by the spring disc. It is necessary to create a magnetic field - and the magnetic circuit is assembled together, providing a circular magnetic flux and activation of the contact pairs. The circuit of the magnetic starter is the following: on the movable pulling part, a system of contacts is fixed, which, depending on the method of installation, when touched by the coil, touch (normally open) or discard (normally closed) from the stationary ones, providing circuit commutation. Contact groups are divided into two types: main (power circuit) and auxiliary (signaling, blocking). It's that simple.

Learning the location

Most contactors allow switching of three pairs of power contact groups and up to a dozen additional ones. The connection scheme of the magnetic starter is described on numerous resources, but it is not understood by all. Anyone who is familiar with such equipment, and so will do everything right, but others "remain with their own". Today we will try to explain in simple language how the connection circuit of the magnetic starter looks.

We pick up the contactor and carefully examine it. All bolted connections are somehow marked. Unfortunately, there is no single standard, or rather each one has its own, although most often manufacturers follow the following designations:

1. Connections 1, 3, 5 on the one hand, and on the other hand, directly opposite them - 2, 4, 6. These are the terminals of the movable and fixed contacts in the power contact groups. The higher the rated current, the larger the bolt dimensions and contact areas.

2. There are several more contacts on the side or on the side, marked 31, 32, etc. Also opposite each other. They serve for signaling and blocking circuits.

3. At the very bottom, on opposite sides of the contactor housings, there are two contacts - A1 and A2. These are the coil pins.

This is the basis. Sometimes in some models a special block from additional pairs of contacts can be installed from above, driven by a rod on the moving part of the magnetic circuit.

Device check

The connection diagram of the magnetic starter can be checked using an indicator. Actually, even at the stage of installation, these devices simplify the work. The indicator "Contact" can be purchased at any electrical shop. It is also possible to use a vertebra from a battery, a light bulb and two wires, but only when checking the de-energized circuits. So, we charge the indicator so that when the two probes come in contact, the lamp lights up or there is a sound signal, which makes sure that the conductor track is present. One probe is placed on the clamp 1 and the other one alternately by 2, 3, 5, 4, 6. This is necessary to check the absence of clamps, which, if any, will lead to interphase closure. If everything is normal, then you need to press a screwdriver on the movable part of the rod (PML, PMA) or hands to press the two parts of the starter (frog), that is, simulate the operation. When checking in this position, the chain should only be on lines 1-2, 3-4 and 5-6.

If auxiliary contacts are hidden and not viewed, then you need to call them to determine the normal state. Suppose that when the state is pressed, the chain of pair 31-32 and 41-42 is shown, while 51-52 and 61-62 are called when the magnetic circuit parts are not closed. The first two are normally open, that is, they do not conduct current without applying voltage to the coil. And the latter are called normally closed, forming a chain with the starter disconnected.

And, finally, with the help of a dial or an indicator, you need to check the coil for integrity. To do this, one touch probe should touch A1, and the other touch A2. The warning light should be on.

All of the above should be performed without wiring connected, and all the more without power supply to the circuit. The circuit of the magnetic starter can be checked without fulfilling this condition, but only by specialists who, for obvious reasons, are unlikely to read about the connection of the electromagnetic contactor.

Roll up your sleeves

The wiring diagram of the magnetic starter connection depends on the equipment fed through it. Therefore, as an example, we consider the classic case when it is necessary to include a three-phase AC motor with a squirrel cage rotor.

We take a three-core cable of a suitable cross-section and connect one side of it to the motor terminals. The strips on the other side are cleaned and fixed with bolted connections on contacts 2, 4, 6 of the starter. If it is more convenient to use 1, 3, 5 because of the features of the installation, then this is allowed. Further, to the terminals 1, 3, 5 we bring three wires from the power machine. That is, after pressing the button of the switch, the voltage of 380 V will be present on the three bolts of the contactor . With any of the lower jaws of the machine there is a wire to the normally closed button "Stop" and a normally open starting, from which the line further leads to the output of the coil A1. The connection diagram of the magnetic starter depends on the voltage to which the coil is designed. If 220 V is indicated on it , then the output A2 must be connected to the ground by the wire. In the case of 380 V instead of the ground, the line must be stretched to one of the two lower jaws of the machine. When checking by the indicator (in the enabled states) between the above sponge and the contact on the stop button of the device, 380 V should be displayed.

How does this scheme work?

The above implementation is the simplest, without interlocks, pick-ups and alarms, however it is fully operational. Even the stop button in this case is not mandatory. After switching on the machine and pressing the "Start" button, the voltage will be applied to the coil of the contactor, it will draw the moving part of the magnetic circuit by the magnetic flux, and the contacts on the rod will work, passing through the voltage 1-2-2,4,5-6. If the button is released, the coil will "fall off" and the chain will disassemble.

Improvement

No less interesting magnetic reverser starter. Physically, this device is two same type of contactors, which, thanks to a special triggering algorithm, are able to change the alternation of phases supplied to the motor. As a result, the direction of rotation changes. A magnetic reverser starter can be implemented independently, by using two devices (KM1, KM2) and making a change to the classical circuit. Also, there are ready-made factory solutions that are not only more compact, but also contain mechanical protection from the "throttle".

Unplanned mode

The correct connection scheme for the reversing magnetic starter necessarily involves the use of a lock. It is necessary for an inquisitive person not to introduce an element of unpredictability into the work of the chain, at the same time pressing the "Forward" and "Back" buttons. The connection of the reversing magnetic starter is performed as follows:

- We connect one contactor in the same way as non-reversing one.

- There are jumpers between terminals 1, 3, 5 of both devices.

- Outgoing lines are crossed as 2-6, 4-4 and 6-2.

- The wire from the control button to the coil KM1 must go through the normally closed contact KM2. And vice versa. This is how the zero protection is realized - an electric lock from the simultaneous pressing of two power buttons. In the case of mechanical protection, such a connection can be omitted, although it will not be superfluous.