# Wiring diagrams for connecting electric three-phase motors to a single-phase network: Instruction + Photo and Video

On homestead or summer cottages, the use of an electric motor is not a rare phenomenon, the main characteristics of which are its power and mains voltage, from which it works. Basically, all electric motors operate from a three-phase 380 volt network.

If you have a connection of three phases, then there will be no problems here. And here's how to connect a 380 to 220 V motor, if a single-phase connection, that is, connecting 2 wires - zero and phase.

To solve this issue, there are various connection schemes.

## General information

Note: Any intrusion into the unit's device, there is a risk of deterioration in the quality of work.

The following schemes are distinguished:

• star-delta;
• using a capacitor.

Typically, the connection to a single-phase network is made using star or delta connections.

### Triangle scheme

This connection has the maximum power output from the motor. In large industries, it is rarely used. Because this circuit is complex and in large production it is not necessary to create such difficult connections. To put the circuit into operation, three starters will be required.

#### The circuit design:

• 1 starter is connected to the current source and to the stator;
• The 2 and 3 starters will be connected to the free ends of the stator ;
• The windings of the second starter are connected to other phases, forming a triangle;
• When connecting the third starter to a phase, the other ends should be slightly shortened, thereby making the circuit a star.

Important : It is not recommended to connect 3 and 2 starters with magnets at the same time, which can create a short circuit and, as a result, an emergency shutdown of the machine.

To avoid such situations, they make a kind of electrical blocking. The essence of the work of which is that when one starter is turned on, the second is automatically turned off, that is, the circuit of contacts is opened.

#### Principle of operation

• When starting 1 starter, the action of the time relay of the electric motor turns on
• After that, the motor starts in a star scheme and starts more powerful work.
• After a certain time, the 3rd starter turns off and turns on.

The motor now operates in a delta pattern with a slightly reduced speed.

• If it is necessary to turn off the power, 1 starter is turned on, then the scheme is periodically repeated.

### The second type of circuit

The electric motor has three outgoing wires. The phase of the supply wire is connected to one, zero to the second, and the third is connected to the network using a capacitor. The direction of movement of the electric motor will be determined by the wire to which the capacitor is connected.

To change the direction of the rotary element, you just need to change the wire connection.

The third indicator is the speed value, which will be equal to the nominal. For example, when connected via a three-phase network, the rotation of the motor is 1300 rpm. min, then with a single-phase connection, the rotation value will be the same.

### Capacitor value in the network

It is quite possible to connect a three-phase asynchronous motor through a single-phase network.

The movement of the shaft will be carried out, but not with the same force as with a three-phase one. In the stator, the electromagnetic fields of the three windings are superimposed, in addition to the fact that there is a rotation of the magnetic current. They also determine the value of the force and torque of the shaft.

In normal mode, connection through a three-phase network can be carried out only by one of the variants of the schemes, i.e.

star or delta. That is why the mains mode connected according to the delta scheme allows a voltage of 380 as nominal. In the case of a single phase, it will be 220 volts. This value will be lower than in the delta circuit and therefore considered safe for electrical operation. However, with a decrease in voltage, there is a decrease in indicators such as electrical power and engine shaft power.

So one of the windings must be connected directly to the electrical network. In order for the maximum return from the rest of the windings, they must be used in combination when connected using a capacitor, which forms phase shifts of the voltage across them. And as a result, we get a connection like a triangle, but with a single-phase circuit.

Also here, the value of the capacitance of the capacitor will play not a small value, since they create a movement of the magnetic field for the rotation of the rotor.

Note: A three-phase motor is capable of moving the maximum magnetic field up to 120g.

And with the help of a capacitor, the movement will be no more than ninety degrees.

So when the engine starts, the capacitor capacity may not be enough. To increase the starting torque, it is necessary to increase its capacity. But in the process, it is possible that this added capacity is superfluous and at the smallest value, the work was more efficient. Therefore, to optimize these indicators, it is better to use 2 heat exchangers.

One must be permanently connected to the network, and the second is connected when the electric motor starts.

Another feature of a capacitor when connected to a three-phase network is its relation to the windings, phase and neutral wires. It can be connected either to zero phase and winding or to phase and winding.Depending on which connection was used, the rotor rotates in which direction. So by adding just one switch to the chain, you can control the movement of the shaft.

A power grid parameter such as inductance is also related to phase shift. Inductance is created by a different ratio of voltage and current. However, if a choke is connected in place of the capacitor. Then it will contribute to a significant decrease in the action of the current in the starting winding, which will create a weak magnetic field in the windings and the engine will not start.

Therefore, the capacitor is the only element suitable for efficiently moving the stator magnetic fields in a motor connected to a single-phase network.

### Types of capacitors

To connect electrical units 380 to 220 Volts, the following paper-type capacitors with a metal case are mainly used - MBGO, KBP, MBGP ... However, all of these types are very large and have a small capacity.

There is still such a type as electrolytic capacitors.

They have a completely different connection scheme. Here added, complicating the circuit elements - diodes and resistors. If the diode fails, then the possibility of an explosion of the capacitor appears, that is, at this moment, it begins to move current with great force.

There is also a third type - CBV capacitors. They are round and lamellar.

They have high qualities, have a large capacity, and are not large in size. It is this type that is recommended by specialists to use when connecting an electric motor 380 to 220.

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