There are several schemes for connecting electric motors. It all depends on what type of machine is used. In everyday life, each person uses a variety of electrical devices, about 2/3 of the total number have electric motors of various capacities with different characteristics in their design.
Typically, when appliances fail, engines may continue to operate. They can be used in other designs: to make home-made machines, electric pumps, lawn mowers, fans. But here you need to decide which scheme to use to connect to a household network.
Motor design and connection
In order to use electric motors for home-made devices, you need to correctly connect the windings. The following machines can be included in a single-phase 220 V household network:
- Asynchronous three-phase electric motors. The electric motors are connected to the network with a "triangle" or "star".
- Asynchronous electric motors, operating on a single-phase network.
- Brush motors equipped with brush design to power the rotor.
All other electric motors must be connected using sophisticated devices designed to start. But stepper motors should be equipped with special electronic control circuits. Without knowledge and skills, as well as special equipment, it is impossible to make a connection. It is necessary to use complex motor connection schemes.
Single and Three Phase Network
A household network has one phase, the voltage in it is 220 V. But you can also connect three-phase electric motors rated for 380 V to it. For this, special circuits are used, it’s almost impossible to squeeze out more than 3 kW of power from the device, as the risk of unusable electrical wiring in the house. Therefore, if there is a need to install sophisticated equipment, which requires the use of electric motors of 5 or 10 kW, it is better to carry a three-phase network into the house. Connecting electric motors with a "star" to such a network is much easier to make than to single-phase.
What you need to connect the motor
The principle of operation of any electric motor is familiar to everyone, it is based on the rotation of the magnetic flux. When connecting single-phase motors, you do not really need a theory, so the following knowledge is enough:
- You must have an idea of the design of the electric motor with which work is performed.
- Know for what purpose the windings are intended, and also be able to carry out installation according to the connection diagram of the electric motor.
- To be able to work with auxiliary devices - ballast resistances or starting capacitors.
- Know how the electric motor is connected using a magnetic starter.
It is forbidden to turn on the electric motor if you do not know its model, as well as the purpose of the conclusions. Be sure to check which connection of the windings is allowed when operating on a 220 and 380 V network. All electric motors must have a metal plate that is attached to the housing. It indicates the model, type, wiring diagram, voltage, as well as other parameters. If there is no data, then it is necessary to ring all the windings with a multimeter, and then connect them correctly.
Collector Motor Connection
Such electric motors are used in almost all household electrical appliances. They can be found in washing machines, coffee grinders, meat grinders, screwdrivers, heaters and other appliances. Electric motors are designed for a relatively short time, they turn on for a few seconds or minutes. But the motors are very compact, high-speed and powerful. And the motor connection diagram is very simple.
It is very simple to connect such an electric motor to a 220 V household network. The voltage flows from the phase to the brush, then through the rotor winding to the opposite lamella. And the second brush removes the voltage and transfers it to the stator winding. It consists of two halves connected in series. The second terminal of the winding is fed to the neutral power wire .
Features of turning on the motor
In order to turn on and off the electric motor, a button with a lock (or without it) is used, but you can use a simple switch. If necessary, both windings are separated and can be connected alternately. This achieves a change in the rotor speed. But there is one drawback of such engines - a relatively low resource, which directly depends on the quality of the brushes. It is the collector assembly that is the most vulnerable point of the engine.
How to connect a single-phase asynchronous motor
In any induction motor, designed to be powered from a single-phase 220 V network, there are two windings - starting and working. As a "collector" is used a cylindrical blank of aluminum, which is mounted on the shaft. It can even be noted that the cylinder on the rotor is essentially a short-circuited winding. There are many schemes for turning on the asynchronous motor, but a little is applied in practice:
- Using ballast resistor connected to the start winding.
- With a capacitor on the start winding.
- Using a push-button or relay starter, a starting capacitor included in the starter winding circuit.
Very often, a combination of a push-button or relay starter is used, as well as a continuously connected working capacitor. Instead of a relay, an electronic key on the thyristor is very often used. Using this switch, a single-phase motor with an additional group of capacitors is connected.
Practical schemes
Asynchronous electric motors have a rather small torque at the start. Therefore, it is necessary to use additional devices, for example, starting relays or ballast resistances, as well as powerful capacitors for connecting single-phase motors. Windings in motors are made with separation into several conclusions. If there are three conclusions, then one of them is common. But maybe four or two.
In order to understand what specific contacts this or that winding is connected, it is necessary to study the motor circuit. If it is not, you will need to dial with a multimeter. To do this, put it into resistance measurement mode. If there is a lot of resistance on the pair of terminals, this means that you measured two windings at the same time. Typically, the working winding of asynchronous motors has a resistance of not more than 13 ohms. At the launcher, it is almost three times higher - about 35 ohms.
In order to connect a single-phase asynchronous motor with the help of a starter, it is enough just to correctly connect all the contacts with wires. In order to start the asynchronous, it is necessary to briefly include additional elements in the circuit - a capacitor or ballast. To turn off the electric machine, simply turn off all windings.
Three phase motors
In three-phase electric motors, significantly more power, as well as torque during startup. Connecting a three-phase electric motor is simple only if there is a socket with three phases of 380 V. But it is problematic to use such motors in domestic conditions, since not everyone has a three-phase network. The windings are connected according to the "star" or "triangle" scheme, it depends on what interfacial voltage in the network.
But in the event that you need to connect such an electric motor to a household network, you have to use a little trick. In fact, you have zero and phase in the outlet. Moreover, “0” can be considered as one of the conclusions of the power source, that is, the phase in which the shift is zero.
To make another phase, it is necessary using an additional capacitor to carry out a phase shift of the power supply. In total there should be three phases, each has a shift of 120 degrees relative to the neighboring ones. But in order to make the shift correctly, it is necessary to calculate the capacitance of the capacitors. So, for every kilowatt of electric motor power, a working capacity of about 70 microfarads, as well as a starting capacitor of about 25 microfarads, will be required. Moreover, they must be rated for voltages from 600 V and higher.
But it is best to connect 380 V three-phase electric motors using frequency converters. There are models that are connected to a single-phase network, and with the help of special inverter circuits they convert the voltage, as a result of which there are three phases that are needed to power the induction motor.