How to connect a three-phase electric motor?
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Three-phase electric motors have found wideuse in solving a number of technical problems: they are indispensable in the drives of lathes, circular sawing machines, drilling machines, etc. Most of the three-phase motors are used in industry, but sometimes they have to work in the home.
In this article, we will show how to connect a three-phase motor to a single-phase circuit.
Three phases into one
The main problem that is in this situationoccurs before the user, - the absence of a three-phase network. Then it is necessary to connect a three-phase motor to a single-phase 220 V network. Of course, this results in a small loss of power, but the engine is, in one way or another, workable.
There are many ways to connect a three-phasemotor to a single-phase network, but the simplest, and therefore the most frequently used, method is the one in which a phase-shift capacitor is applied through which the third motor winding is fed.
Features of inclusion
Before connecting a three-phase motor,see how the motor winding is connected. In the event that they are connected in a triangle pattern (see Figure 1), the engine will lose the least in power,otherwise, the engine's power will be about 70% of the power it can produce when it is switched on in the three-phase supply circuit.
An important point! In the figure you can see the terminal blocks, but in many cases instead of them you will deal with bundles of wires, and in order to separate them from each other and to understand which contact each of them belongs to, it is necessary to "ring" the contacts using a special device, for example, a multimeter. As a result, it is necessary to achieve a pairwise connection of C1-C6, C2-C4, C3-C5 (see Figure 2).
To connect a three-phase motor to a networkin addition to the engine itself, you will need two capacitors - a starting and working capacitor, and a button. All these elements must be soldered according to the diagram (see Figure 2).
Calculation of capacitors
To calculate the required nominal capacity of the working capacitor,use the formula - Cp = 4800 * I / U orCp = 66 * P, where I, U, P - current strength, voltage, power of the circuit, respectively. The nominal value of the starting capacitor, as a rule, is three times the nominal value of the worker. By the way, if the power of your circuit is less than a kilowatt, you can do without a starting capacitor.