How to get three phases from one

How to get three phases from one

Hi all! Today I will show you how to get a three-phase network from a regular single-phase 220 V network, and at no particular cost. But first, I’ll tell you about my problem that preceded the search for such a solution.
I had a powerful Soviet table saw (2 kW), which was connected to a three-phase network. My attempts to power it from a single-phase network, as is usually customary, were not possible: there was a strong power drawdown, the starting capacitors got hot, and the engine itself got hot.
Fortunately, at one time I spent due time searching for a solution on the Internet. Where I came across a video where one guy made a kind of splitter using a powerful electric motor. Next, he installed this three-phase network around the perimeter of his garage and connected to it all other devices requiring three-phase voltage. Before starting work, he came to the garage, started the dispensing engine and it worked until he left. In principle, I liked the solution.
I decided to repeat it and make my own splitter. As an engine, I took an old Soviet one with 3.5 kW of power, with star-connected windings.

Scheme


The whole circuit consists of just a few elements: a general power switch, a start button, a 100 uF capacitor and a powerful motor itself.
How to get three phases from one

How does it all work? First, we supply single-phase power to the distributing motor, connect the capacitor with the start button, thereby starting it. Once the motor has spun up to the desired speed, the capacitor can be turned off. Now you can connect a load to the output of the phase splitter, in my case a tabletop circular and several more three-phase loads.
How to get three phases from one

The body of the device - the frame is made of L-shaped corners, all equipment is fixed to a piece of OSB sheet. Handles for carrying the entire structure have been redesigned on top, and a three-pin socket is connected to the output.
How to get three phases from one

After connecting the saw through such a device, there was a significant improvement in operation, nothing gets hot, there is enough power, and not only for the saw. Nothing growls or buzzes like it did before.
It is only advisable to take the distributing motor at least 1 kW more powerful than the consumers, then there will not be a noticeable drop in power under sudden load.
No matter who says anything about the sine not being pure or it will give nothing, I advise you not to listen to them. The voltage sine wave is clean and split exactly 120 degrees, as a result the connected equipment receives high-quality voltage, which is why it does not heat up.
The second half of the readers who will speak in the 21st century and the large availability of three-phase voltage frequency converters, I can say that my solution is several times cheaper, since the old motor is quite easy to find. You can even take one that is unsuitable for the load, with weak and almost broken bearings.
My phase splitter in idle mode does not consume so much: 200 - 400 W somewhere, the power of the connected tools increases significantly compared to the usual connection scheme through starting capacitors.
In conclusion, I would like to justify my choice of this solution: reliability, incredible simplicity, low costs, high power.

Watch the video


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Comments (20)
  1. Calle
    #1 Calle Guests August 18, 2018 01:07
    0
    If you have an extra engine, the idea is normal. But you need to do some math in your head using numbers. Firstly, if this engine-generator is switched to a triangle, then it will be able to deliver twice as much power (approximately). The connected load (saw) can have a power of approximately 1/3 of the generator power. And if you leave working capacitors in the generator, then 1/2 the power of the generator. The idea is good because a three-phase saw can operate at full power. BUT YOU NEED TO KNOW THAT THE RESULT IS NOT 380V, BUT 220V. The overall efficiency of the system will be reduced due to the heat generated by the generator. Previously, your saw with a capacitor circuit could be loaded up to 1/2 of its power (approximately).Previously, it got hot because you tried to load it 100%, or you didn’t switch the saw to a triangle and chose the wrong operating capacitors. The starters heated up because you chose electrolytic ones.
  2. Guest Alexander
    #2 Guest Alexander Guests 19 August 2018 18:44
    5
    I was touched by the phrase “Phase splitter...”))). The electric motor operates in generator mode, more precisely in this case, one winding shifted in phase. And one more thing: you cannot spend 600 watts and get 2 kW! Or is it a perpetual motion machine, energy from nowhere???
    1. MIX
      #3 MIX Guests 20 August 2018 12:06
      3
      Everything is correct. It is a phase splitter. And the engine operates in the mode of an asynchronous three-phase generator. And 200-600 W is at idle. And under load, the load power is added accordingly. Learn materiel.
    2. Motarych
      #4 Motarych Guests September 10, 2018 04:47
      2
      And you continue to be touched. I see it every day at work. They are installed on electric locomotives. Previously, there was a phase splitter - an asynchronous type electric machine with a generator winding and a relay that cuts off the FR at sufficient speed. On Ermak they simply install asynchronous. One terminal is the direct phase from the auxiliary transformer winding. The first half-cycle is taken, the second phase is the negative half-cycle, and the third phase is shifted on the capacitor cascade. What touched you, I don’t know.
    3. Guest Alex
      #5 Guest Alex Guests 20 October 2018 21:59
      1
      the phase splitter is included in the design of the electric locomotive and has been used for 50 years
  3. Ivan Vasiliev
    #6 Ivan Vasiliev Guests August 20, 2018 01:30
    6
    This is all nonsense. No three phases will work. Instead of a linear voltage of 380V (phase A, B, C), phase 220V is supplied (any of the phases and N zero). This voltage is enough to rotate the rotor, but not for starting. Therefore, they use a regular one a push of the rotor shaft or a capacitor, which, when discharged, shifts the existing phase by 120 degrees and thereby briefly becomes the “third” phase. Any electric motor of a three-phase network will not start on two phases or on phase and N. And the capacitor capacity of 100 μF is not enough for a 3.5 kW motor. Typically, a 70 µF capacitor is used per 1 kilowatt of engine power.
    1. alec
      #7 alec Guests 30 August 2018 21:37
      0
      Theoretically, the maximum phase shift of a capacitor is 90 degrees without load.
    2. Motarych
      #8 Motarych Guests September 10, 2018 04:50
      2
      Now go study the circuit diagram of any AC electric locomotive.
  4. Guest Nikolay
    #9 Guest Nikolay Guests 20 August 2018 15:56
    0
    Advice that is 30 years late!!! Not everyone will be able to get a 3 kW engine; you can buy a new one and install this strange device. A new three-phase asynchronous machine costs approximately 7 thousand rubles, plus other components and materials, and the result is a bulky monster. It’s easier to save your time and nerves and buy a device called a power supply unit for three-phase motors from a single-phase network. The device is compact and costs only around 9 thousand. I would choose this option, since first of all, the skin is not worth repairing...
  5. Vasya
    #10 Vasya Guests 20 August 2018 16:38
    3
    Ivan Vasiliev support BRAD SIVOY
  6. Mikhail Ivanov
    #11 Mikhail Ivanov Guests 23 August 2018 13:18
    4
    Complete nonsense. You can, of course, make a 380-volt generator from an asynchronous motor, but definitely not in this way. Judging by the diagram, the engine here works as an autotransformer, and the effect from it will be the same.
  7. Ivan Petrovich
    #12 Ivan Petrovich Guests 9 September 2018 17:04
    1
    This method has always been used on AC electric locomotives, and may still be used today
  8. Tagir
    #13 Tagir Guests 10 September 2018 10:05
    0
    Great idea, too bad I didn't know this earlier...
  9. Guest Alexander
    #14 Guest Alexander Guests 24 September 2018 16:53
    3
    It’s a normal, proven method, I’ve been using it for 8 years, it’s better to use a low-speed induction motor as a phase converter (I read an article in an old Soviet magazine), mine is 4 kW * 960 rpm, with a 120 µF capacitor it starts normally, a circular circuit and a compressor work from it , industrial drilling machine, of course, not all together..
    1. Sector
      #15 Sector Guests 31 January 2019 19:57
      2
      Isn't it possible that the city boiler room is powered by you?
  10. Ricardo Milos
    #16 Ricardo Milos Guests 11 February 2019 23:56
    1
    in the magazine modeler designer for 1972 No. 4 there is a diagram of a splitter on the chokes and a diagram from a patent somehow came across, but it’s working or not, I don’t care. and from the asynchronous system the worker checked it himself.