Powerful transformer from three low-power ones

Powerful transformer from three low-power ones

Once I needed a powerful transformer with bipolar power supply for a low-frequency power amplifier. I searched the bins and didn't find anything like it. Unfortunately, there was nothing like this for sale locally either. Then 3 identical transformers from old music centers caught my eye. And a great idea came to mind: to make one powerful transformer out of three small ones.
Powerful transformer from three low-power ones

Making a powerful transformer from three small ones


We disassemble the magnetic circuit of all transformers. To do this, we first knock out all the “I”-shaped elements located in a checkerboard pattern, and then all the “W”-shaped plates.
Powerful transformer from three low-power ones

We remove layers of insulation and windings from the frames.
Powerful transformer from three low-power ones

We saw off the end of two frames only on one side. And the third has both ends, so that only the side plates remain.
Powerful transformer from three low-power ones

Using super glue we glue the frame together.
Powerful transformer from three low-power ones

We wrap it with the first insulating layer for proper fixation. We remove possible spreading of the glue with a file after hardening. The entire surface inside must be smooth and hard, otherwise the core will not fit tightly.
Powerful transformer from three low-power ones

We measure the internal cross-section of the future magnetic circuit and, using special formulas, calculate the number of turns for the primary and secondary windings.
Powerful transformer from three low-power ones

We wind the first winding, it is 268 turns according to calculations (for 230 V power supply). But I brought it up to 300 to make some reserve and reduce the no-load current.
Powerful transformer from three low-power ones

We wrap one turn to another in layers. We isolate each layer.
Powerful transformer from three low-power ones

The primary winding is ready. We draw conclusions through insulating tubes.
Powerful transformer from three low-power ones

We insulate in two layers to create reliable galvanic isolation.
Powerful transformer from three low-power ones

We wind the secondary winding. For a “35 V-0-35 V” output with a total voltage of 70 Volts, it is necessary to wind 84 turns, tapped from the middle.
Powerful transformer from three low-power ones

We make a tap from the middle, from 42 turns.
Powerful transformer from three low-power ones

The result was a secondary winding wound with 1.2 mm wire.
Powerful transformer from three low-power ones

We assemble the transformer core. First, we install “W”-shaped plates in a checkerboard pattern.
Powerful transformer from three low-power ones

And at the very end, “I” is figurative.
Powerful transformer from three low-power ones

Checking the transformer. To do this, for safety, we connect the primary winding to the network through an incandescent lamp.
Powerful transformer from three low-power ones

Everything is working. We measure the voltage at the output of the secondary winding. The result was approximately 32 Volts on each arm.
Powerful transformer from three low-power ones

In general, the idea is good, the transformer works, does not heat up, there is enough power.

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Comments (11)
  1. Guest Pavel
    #1 Guest Pavel Guests 11 November 2019 22:46
    0
    It is energetically more profitable to assemble not 3>1 in a line, but 1.5>2 in height (despite the forced gap).
  2. Eduard Nikolaevich
    #2 Eduard Nikolaevich Guests 12 November 2019 14:03
    8
    These Indians are entertainers... They have a different mindset, however...
    If they were not burnt, then it was possible not to spoil the trans-s at all, rewind only the secondary windings to 2x12V (1.2mm wire) and connect them in series.
    Make one out of 3 only if you are completely bored and have nothing else to do. All the same, the mass of copper and the mass of steel in 1 “triple” and in 3 singles are the SAME, i.e. It is economically IMPOSSIBLE to remake a “3 in 1”. Moreover, the 3 “small” trans-s have a much larger cooling surface, which increases reliability. The only justification is aesthetic preferences, or the aforementioned boredom...
    1. Nik
      #3 Nik Guests 27 November 2019 21:33
      0
      If there are three trans, where do you get the middle pin?
  3. Old Sergei
    #4 Old Sergei Guests 14 November 2019 22:39
    3
    Original. Good for the enthusiast. It is even justified to change the output voltages. And if you don’t need to change them, you don’t need to fence this whole garden! It is enough to parallelize the primary windings of the SAME transformers, and connect the secondary windings either in parallel, phasing them, or in series, if you need to increase the voltage. Phasing is required. Labor intensity will drop by two orders of magnitude!
  4. Al Zeev
    #5 Al Zeev Guests November 23, 2019 10:26
    3
    We turn on three primary ones in parallel and three secondary ones in parallel, ensuring that the output coincides with the sinusoid and - you're done. Why all this trouble?
  5. Guest Sergey
    #6 Guest Sergey Guests November 30, 2019 10:28
    2
    Why bother with moving away from the midpoint? This is how the secondary windings were wound in the tube era, under a two-anode kenotron. Today - bridge rectifier and all that. Instead of two diodes - four. The asking price is a few rubles
    1. Guest Oleg
      #7 Guest Oleg Guests December 26, 2019 05:38
      2
      Bipolar power supply won't work that way, that's what the tap is for
      1. A.S.
        #8 A.S. Guests 3 January 2020 15:02
        0
        who said it won't work?
        1. Bob
          #9 Bob Guests 6 January 2020 22:05
          2
          If you make the middle point with containers, it will work, but in terms of consistency, the middle point, I mean, will be floating. If we connect acoustics to it, then we are getting money for a good brand, because what kind of SunHai thread will distort the sound so much that you won’t even want to listen! And with PHYSICAL cf. The point can be used to connect acoustics without a capacitor!
  6. Guest Alex
    #10 Guest Alex Guests 9 January 2020 12:17
    2
    Unnecessary difficulties - we take not 3, but 4 trances and connect the output windings of each pair in series. The homemade amplifier has been working great for about 20 years now. I just changed the electrolytes to modern, larger ones.
  7. Xo-xo
    #11 Xo-xo Guests 15 May 2021 04:42
    1
    "Let's swear" ->

    There is no such word in Russian! There is "motaem".