Motor connection in three phases

We can rightfully say that electric motors are the basis of modern civilization. With the current level of progress, they represent one of the most effective solutions for converting one type of energy into another. Electric motors are so widespread that sometimes, looking at this or that device, it is impossible even to assume that it uses some kind of electric motor. For example, few people know that in some mobile phones the vibration mode is realized due to the rotation of the shaft of a compact engine with an eccentric mounted on it. Not surprisingly, even fewer people know how to connect the motor. Although, frankly, nothing complicated in this. To understand how the motor is connected, it is not necessary to finish electrical courses or to understand the interaction of magnetic fields inside the device body.

Roll up our sleeves ...

Connection of the electric motor does not start at all from the voltage supply to the terminals, but from the inspection of the device specification. On any electric motor (if, of course, it was not in the hands of vandals and not operated in an aggressive environment), there is always a small sign that indicates the type, efficiency, voltage and current, nominal shaft speed, If you ignore this data and connect the motor, it is possible to damage the power supply, the conductors or the motor itself.

One of the key moments is the power (in kilowatts). Its value affects the cross-section of the core of the wire, which will be supplied with voltage. The dependence of the conductor cross-section on current and power is given in a special table (can be found in the PUE).

Solutions for alternating current

As more widely distributed asynchronous motors, then we will consider them. Opening the cover of the barn (terminal box), you can see the dielectric block with a number of leads. For motors designed for three-phase networks, there may be 3 or 6 contacts. In the first case, the connection is simple: for each terminal a phase (380 V) is applied, and if necessary, change the rotation, any two of them must be interchanged.

The 6-pin electric motor circuit is more flexible. Usually on the plate in the column "Voltage" two values are indicated at once: 220 and 380 Volts (or 380 and 660). This means that, depending on the method of power supply, the potential on the windings will be different. There are two variants: "triangle" and "star". Inside the engine there are three windings, the beginnings and ends of which, respectively, are designated C1-c4, C2-c5, C3-c6. The label always indicates the connection of the voltage, that is, 220/380 at "triangle / star" means that the connection scheme of the internal windings, for example, in a star, is used for the 380 V network. It should not be confused unless, of course, To carry out an unscheduled repair of the electric motor.

We connect the conclusions

Suppose that the desired voltage is selected. On the plate we define the connection scheme. It remains to correctly establish the jumpers between the terminals and draw the voltage. For the star, bridges between C4-C5-C6 contacts should be installed, and opposite phases should be connected to C1, C2 and C3. For the triangle, the scheme is different: bridges are placed between C3-C5, C2-C4 and C1-C6. In a two-wire network, a third "phase" can be obtained by switching on an auxiliary capacitor. This scheme is widely available, so here it is not considered.

Each of the ways of connecting the internal windings has its own peculiarities: one has high currents and power, and the other has a smooth operation. Select the desired scheme should be based on the capabilities of the network and the tasks to be solved with the help of the electric drive.