Connecting a three-phase electric motor to a single-phase network

A 3-phase motor can be used to operate from a single-phase household AC network with a voltage of 220 volts. Rework is possible even if there is no extensive experience in electrical work with minimal installation skills. The costs of additional circuit elements are low.
Connecting a three-phase electric motor to a single-phase network

Types of winding connections


A three-phase motor contains a stator - a stationary part with fixed wire coils. They are offset relative to each other along the circumference by 120 angular degrees. Alternating current, passing through the windings, creates a changing magnetic field that pushes the moving part of the engine - the rotor, or as it was called before - the armature.
There are two known ways to connect windings to each other:
Connecting a three-phase electric motor to a single-phase network

  • Star - the first ends of the windings are connected to each other, and the phase conductors of the network are connected to the second terminals of the coils.
    Connecting a three-phase electric motor to a single-phase network

  • Triangle - the coils are connected in series one after another, the end of the third winding is connected to the beginning of the first. Schematically they form a triangle, to the vertices of which the phases are connected.
    Connecting a three-phase electric motor to a single-phase network


Stages of work:


1. Having carefully examined the electric motor, find a socket (usually an aluminum plate) with information about the parameters.There is no need to undertake modifications to a motor with a power of more than 1 kW (1kW). The inscription DY 220/400 means that the motor can be turned on in both the triangle (D) and star (Y) configurations. The operating voltage is 220 volts single/or 400 three-phase. Terminals marked L(1÷3) for connecting phases.
2. As a standard, the coils of a 3-phase electric motor are star-connected. Changing the position of the strip jumpers will create a "triangle" pattern.
3. After this, connect L1 to the phase conductor, and L3 to the neutral wire. We connect the middle terminal (L2) to a shifting capacitor, the second terminal of which is connected to phase or zero. This determines the direction of rotation of the armature. A motor power of 100 W will require a capacitance of 8÷10 µF, for 0.25 kW a capacitor of 20 µF is needed.
4. It is convenient to quickly change the direction of rotation by switching the capacitor from the phase conductor to the neutral conductor. A two-pole switch will supply power to the motor.

Connection to a single-phase network


Remove the cover of the electric motor junction box, gaining access to the jumpers.
Having previously unscrewed the fastening nuts, change the position of the jumpers, changing the connection diagram of the windings to a “triangle”. After this, tighten the nuts securely and replace the box cover, noting the 1st, 2nd and 3rd phase connection wires.
Connecting a three-phase electric motor to a single-phase network

Determine the middle winding, cut the core, strip the insulation. Crimp the ends with a terminal lug, if any, and connect a capacitor into the gap.
Connecting a three-phase electric motor to a single-phase network

It is convenient and reliable to connect the circuit using terminal pairs. By connecting the wires from the motor and capacitor to the connector, ground, phase and neutral are supplied from the other end. Carefully tightening the terminal screws will ensure reliable electrical contact.
IMPORTANT! The motor has a conductor with yellow-green insulation. It is connected to the body.Connected through the third contacts of the cord plug and socket with grounding, it protects against voltage breakdown across the motor mass. You cannot connect other electrical wires to it - only the yellow-green end of the power plug.
The functionality of the circuit can be checked by connecting the wire from the capacitor to the phase and turning on the power 220. If all parts are in good condition, the motor should rotate the rotor in one direction.
Having removed the power, we switch the capacitor to the neutral conductor - the motor rotates in the opposite direction. Having chosen the appropriate direction, we leave the desired connection constant.
Connecting a three-phase electric motor to a single-phase network

A quick change of the direction of rotation to the opposite one will be provided by a switch connecting the capacitor to phase or zero.
IMPORTANT! Changing direction is allowed only after the power is turned off and the rotor has completely stopped.

Safety


Reworking the electric motor involves working on a 220 volt network. Careless handling or carelessness in work is associated with a threat to life or health. Do not leave connections without proper insulation. Restrict access of unauthorized persons to the installation until it is completed.

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Comments (12)
  1. Guest Victor
    #1 Guest Victor Guests 11 February 2019 18:28
    11
    "The inscription DY 220/400 means that the motor can be switched on both in the triangle (D) and star (Y) configurations. The operating voltage is 220 volts single/or 400 three-phase."!!!!! Author, edit this STUPIDITY you wrote!!! 220/400 - means 3-phase voltage!!! And no other way if you have a 3-phase motor! D-delta connection for 220 volts 3-phase or Y-star for 400 volts 3-phase.
    1. Guest Vladimir
      #2 Guest Vladimir Guests 13 February 2019 10:53
      4
      Yes, everything is written correctly. And connection and calculation of capacity. A classic scheme from the times when there were no frequency converters. The only drawback with this connection is that the motor power on the shaft decreases. Nowadays, anyone who has “an extra 10-15 thousand” should buy a frequency generator powered by 1ph. 220v at 3ph output. 220v. and don't bother.
  2. Anatoly
    #3 Anatoly Guests 12 February 2019 15:44
    6
    The author probably doesn’t know that there is a three-phase 220 v.
    1. Oksana
      #4 Oksana Guests March 26, 2019 08:56
      2
      You don’t know that there is no three-phase 220 V. Three-phase only 380, 660, 1020, etc. Yes, and there is also a three-phase 127, but this is not ours
      1. Gennady
        #5 Gennady Guests September 8, 2020 12:57
        1
        Three-phase 220 V exists even here. In this case - phase - 127, and linear - 220. I use this type...
  3. Guest Yuri
    #6 Guest Yuri Guests 18 February 2019 12:04
    2
    The inscription 220/400 means the linear voltage of the network when connecting the windings of the electric motor in “triangle” and “star”, respectively. And not otherwise.
  4. KiteBlack
    #7 KiteBlack Guests 22 February 2019 22:00
    1
    "...A motor power of 100 W will require a capacitance of 8÷10 μF, for 0.25 kW a capacitor of 20 μF is needed....: - yeah - shazzzz! The capacity is selected individually for each engine. The lower the operating speed, the less required capacitance. The criterion for the correct selection of a capacitor is the equality of voltages in the phases under load. And since the load, as a rule, is not constant, it is impossible to select the capacitance accurately. Moreover, with a working capacitance, even a low-speed engine will not start. In any case, a starting , ten times higher than the working...
  5. Guest Alexander
    #8 Guest Alexander Guests 4 March 2019 20:28
    0
    The voltage of the capacitor, if it is designed to operate on alternating current (for example, MBGC), must be at least 250 V (during operation it may exceed 250 V depending on the load). And if it is intended to operate on direct current, then it should be at least 400 V.
  6. Guest Alexander
    #9 Guest Alexander Guests 5 March 2019 19:28
    0
    The voltage of the capacitor, if it is designed to operate on alternating current (for example, MBGC), must be at least 250 V (during operation it may exceed 250 V depending on the load). And if it is designed to operate on direct current (for example, MBGO, K75-40), then it should be at least 400 V.
  7. Sergey Natalevich
    #10 Sergey Natalevich Guests March 16, 2019 10:14
    1
    I propose 2 schemes for connecting a 3-phase electric motor to a single-phase network
  8. Sergey Natalevich
    #11 Sergey Natalevich Guests March 16, 2019 10:22
    0
    For capacitors: use K78-17 (450V 50Hz) or, as a last resort, K75-10 (250V 50Hz)
  9. Guest Alexander
    #12 Guest Alexander Guests 26 July 2019 23:31
    1
    Now I look at the fact checkers and am amazed, if you are so smart, then why don’t you publish such posts yourself, but slander and insult anyone on the Internet... yes please, that’s us in an instant!