Starting a three-phase motor from a single-phase network without a capacitor

Starting a three-phase motor from a single-phase network without a capacitor

The article is devoted to the possibility of starting a three-phase asynchronous motor with a power of 250 W from a 220 V network not using a starting capacitor, but using a home-made starting electronic device. Its circuit is very simple: on two thyristors, with thyristor switches and transistor control.

Device diagram


Starting a three-phase motor from a single-phase network without a capacitor

This engine control is little known and practically not used. The advantage of the proposed starting device is that the loss of engine power is significantly reduced. When starting a three-phase 220 V motor using a capacitor, the power loss is at least 30%, and can reach 50%. Using this starting device reduces power loss to 3%, with a maximum of 5%.
Starting a three-phase motor from a single-phase network without a capacitor

Starting a three-phase motor from a single-phase network without a capacitor

Single-phase network is connected:
Starting a three-phase motor from a single-phase network without a capacitor

The starting device is connected to the engine instead of a capacitor.
Starting a three-phase motor from a single-phase network without a capacitor

A resistor connected to the device allows you to regulate engine speed. The device can also be turned on in reverse.
Starting a three-phase motor from a single-phase network without a capacitor

An old Soviet-made engine was used for the experiment.
Starting a three-phase motor from a single-phase network without a capacitor

With this starter, the engine starts instantly and runs without any problems. This scheme can be used on almost any engine with a power of up to 3 kW.
Starting a three-phase motor from a single-phase network without a capacitor

Note: in a 220 V network, it simply does not make sense to turn on motors with a power of more than 3 kW - household electrical wiring will not withstand the load.
The circuit can use any thyristors with a current of at least 10 A. Diodes 231, also 10 A.

Note: the author has 233 diodes installed in the circuit, which does not matter (only they run at a voltage of 500 V) - you can install any diodes that have a current of 10 A and hold more than 250 V.
The device is compact. The author of the circuit assembled the resistors simply in sets, so as not to waste time selecting resistors at their nominal value. No heat sink required. A capacitor, a zener diode, and two 105 diodes were installed. The circuit turned out to be very simple and effective in operation.
Starting a three-phase motor from a single-phase network without a capacitor

Recommended for use - assembling the starting device will not create problems. As a result, when connected, the engine starts at its maximum power and with virtually no power loss, in contrast to the standard circuit using a capacitor.

Watch a video about how the device works


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Comments (48)
  1. Guest Nikolay
    #1 Guest Nikolay Guests 10 August 2018 14:50
    18
    Hello! I'm interested in your device. If you don't mind, could you share the printed circuit board so that you can have a completed device at your disposal?
  2. victor
    #2 victor Guests 10 August 2018 17:23
    15
    I agree with the request in the previous comment. Will the indicated thyristors and diodes withstand it if the motor is 2-3 kW?
  3. Guest Oleg
    #3 Guest Oleg Guests 10 August 2018 18:27
    10
    if possible please send one sample
  4. Basil.
    #4 Basil. Guests 10 August 2018 18:44
    4
    The device is interesting. And if you turn on the engine with a star, will it start?
    1. Sergey K
      #5 Sergey K Visitors 10 August 2018 23:14
      3
      It will start, why not? It’s just that if the engine is 380, but connected to the network 220, then the power will be much less
      1. Guest Evgeniy
        #6 Guest Evgeniy Guests August 11, 2018 00:20
        7
        A three-phase motor, when turned on correctly (star on a 380-volt network or triangle on a 220-volt network), does not change power.
        Power is lost when the motor is turned on in a single-phase network when the phase-shifting circuit is not selected accurately enough.
        And this happens almost always, because... The circuit parameters need to be changed depending on the load. In particular, when starting a powerful engine, it is recommended to increase the capacitor capacity by connecting an additional starting capacitor in parallel to it.
  5. Calle
    #7 Calle Guests 10 August 2018 21:17
    9
    Explain the principle of operation. Regulating the speed of a conventional asynchronous motor is fantastic.
    1. Guest Sergey
      #8 Guest Sergey Guests 2 September 2018 20:34
      2
      No, it’s not science fiction, this has been used for a long time
  6. Guest Vlad
    #9 Guest Vlad Guests 10 August 2018 21:23
    4
    This diagram is from RADIO magazine, in the 90s. I assembled it, but with my current engine I couldn’t start it. Perhaps it doesn't work with some people? I didn’t fully understand it then, but the elements didn’t burn out and were in good working order.
  7. Igor Averyanovich Borisov
    #10 Igor Averyanovich Borisov Guests August 11, 2018 05:19
    4
    Well, let's say, firstly, there are so many household appliances in apartments today that a power of 3 kW is nothing, it's about 14A, secondly, thyristors must have a heat sink, otherwise there will be overheating and failure, and thirdly, is it worth reinventing the wheel?
  8. Nik
    #11 Nik Guests August 11, 2018 09:32
    4
    Instead of two diodes and two thyristors, you can install one triac. Judging by the diagram, any power regulator should be suitable that cuts the half-cycle.
  9. Calle
    #12 Calle Guests 11 August 2018 12:50
    3
    The most this circuit can claim to be is a starting device. What is shown in the video
    divorce, deception. An asynchronous motor cannot remain in a state of unspinned rotor to the nominal for more than a few seconds; it will burn out. In the video, the motor is connected to the network through a current limiter, such as a capacitor, or to a low voltage (24v).
    1. Guest Pavel
      #13 Guest Pavel Guests 25 September 2018 21:10
      2
      the diagram shows an elementary generator, the use of a triac in this circuit is impossible since the thyristors open in the circuit one by one and form the third phase, diodes are needed to protect the thyristors and at the same time to close them, since thyristors do not work very well with inductances
  10. Alexander Vasilievich
    #14 Alexander Vasilievich Guests 11 August 2018 14:33
    2
    The scheme is good. Tested on many types of three-phase motors. It works "almost" great. You can find a full description of how this circuit works in the Radio magazine.Somewhere during the years 1995-2003. Sorry, I forgot the year and number. When I have time, most likely one of these days, I’ll find the article and write it again. But now work and a garden and a house... It’s enough without it.
    The author should have made a link to the source. But anyway, thanks to the author of the article for “conveying” the information to the people.