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This workshop will be a bit controversial and will cause more than one scattered opinion. I want to share how to make a powerful rectifier from a microwave oven transformer - a power supply, to the voltage I need.
Very often, microwaves fail and are thrown into the trash. I recently broke another one and I decided to give a second life to its transformer.
The transformer there is step-up and usually converts 220 V to a high voltage of 2000-2500 V, necessary to excite the magnetron.
I saw how many people remake these transformers either as a resistance welding machine or an arc welding machine. But I never saw that they made powerful power supplies from it.
After all, the transformer is very powerful, about 900 watts, and this is not enough. In general, I will show you how to rewind the transformer to the voltage you need.

We disassemble the transformer from the microwave


Powerful microwave transformer power supply

Typically, a microwave transformer contains three windings. The most numerous, wound with the thinnest wire is a raising, secondary one, at the output of which 2000-2500 V. We do not need it, we will remove it. The second winding, thicker, with less wire compared to the secondary is a 220 V network winding. Still, between these two massive windings, there is the smallest one, which consists of several turns of wire. This is a low-voltage winding of about 6-15 V, an outstanding voltage to the magnetron glow.

Cut the seams of the magnetic circuit


Powerful microwave transformer power supply

It is necessary to cut down the seams that hold together “W” -shaped plates and “I” -shaped. The seams of the Chinese manufacturer are as strong as they seem. You can cut them with a grinder or even split them with a chisel and hammers. I used a grinder, this is a humane way.

Remove the coils


Powerful microwave transformer power supply

Powerful microwave transformer power supply

We remove all the coils. If they are very firmly stuck - tap gently with a rubber mallet. We only need a winding for 220 V, we remove the rest. We put the primary winding back to 220 V and put it down the "Ш" -shaped core.
Powerful microwave transformer power supply

Secondary winding calculation


Now we need to calculate the number of turns of the secondary winding. To do this, you need to know the transformation ratio. Usually, in such transformers it is equal to unity, therefore one turn of the wire will produce one volt. But this is not always the case and you need to double-check it.
We take any wire and wind 10 turns of wire on the core. Then we collect the core and clamp it with a clamp so that it does not fall apart. Be sure to supply 220 V to the primary winding through the fuse. At this time, we measure the voltage at the output of a 10-turn winding. In theory, it should be 10 V. If not, then the transformation coefficient is not the same as usual and you need to make calculations to calculate the voltage for your winding. All this is not difficult, mathematics is fifth grade.
I have two transformers available. I will do one at 500 V, the other at 36 V. You can do it for any other voltage.

500 V transformer coil winding


The transformation ratio of my instance is one to one. And to wind the winding at 500 V, I need to make 500 turns of wire on the coil, respectively. Take the wire.
Powerful microwave transformer power supply

Of course not like that, but wound on a drum. We estimate the current strength and the volume of the coil. From these values, select the diameter of the wire.
Powerful microwave transformer power supply

Here is such a simple device I gathered for winding a coil.The core itself is made of wood, the sides are made of plexiglass. You can fix it on a drill or screwdriver.
Powerful microwave transformer power supply

Winded, assembled, connected. I measure the output voltage, I almost got it - 513 V, which is acceptable for me.
Powerful microwave transformer power supply

36 V transformer


The 36 V winding can also be wound manually by taking the appropriate wire. To put on and straighten the winding on the core, you can use such wedges, see photo.
Powerful microwave transformer power supply

After the whole winding is stretched, into the holes formed, after removing the wedges, put tightly pressed paper. This is my primitive way. Then I recommend impregnating the winding with epoxy, otherwise it will be very buzzing.

Error handling


I rewound the winding to make it denser and more powerful. To do this, I wound it with a double wire, instead of one thick one. In the end I will connect them.
Powerful microwave transformer power supply

After all the windings are fixed, it is time to assemble the transformer core. To do this, we fix the entire structure with a clamp and arc weld the same places as before. There is no need to make a thick seam, everything should look as it was.
Next, for my rectifier I will need:



Powerful microwave transformer power supply

I will load the rectifier by 20 A, of course the diode bridge must be installed on the radiator.
Also, if you will use a metal case like me, then do not forget to ground it.

About security


Be careful when connecting the transformer, never rush and double check everything. Only connect the transformer through a fuse to avoid a possible short circuit. Do not touch live parts while the transformer is in operation.
Also, when processing metal, be sure to be careful and use eye protection.
Remember that all actions you do at your own peril and risk!
All the best!
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Comments (15)
  1. ALEXANDER KOLICHNICHENKO
    #1 ALEXANDER KOLICHNICHENKO Guests February 23, 2018 10:50
    3
    I have a network winding to idle after 30 minutes is hot, it looks like it doesn’t hold anymore, it’s not without reason that it blows a fan.
    1. Petrovich
      #2 Petrovich Guests February 23, 2018 16:23
      1
      Try to check the windings, maybe there is a problem in them, and the load may be to blame
    2. Alexander
      #3 Alexander Guests February 23, 2018 17:53
      0
      So inter-turn in the winding.
    3. p5d
      #4 p5d Guests February 25, 2018 9:53 p.m.
      0
      The thought is right!
  2. Alexander
    #5 Alexander Guests February 23, 2018 17:57
    1
    The transformation ratio depends on the winding of the primary and secondary, the thickness of the iron. If you do not take into account the transformation coefficient of iron, then the voltage on the windings will be equal to the ratio of the number of turns of the primary and secondary windings, and not the transformation 1. And since you do not know the primary winding, it is only experimentally possible to find out how many volts per one turn, nothing else.
    1. p5d
      #6 p5d Guests February 25, 2018 21:50
      1
      It would not hurt you, sir, to read a book on electrical engineering. For the transformation coefficient of iron, you are entitled to the Nobel Prize. The furnace transformer is not designed for long continuous operation (PV no more than 50%) and therefore has limited use.
  3. nail
    #7 nail Guests February 23, 2018 18:32
    3
    too much gravity and doubtful reliability
  4. Guest Alex
    #8 Guest Alex Guests March 3, 2018 08:44
    4
    That's right, microwave trans is not designed for continuous operation. no need to talk about inter-turn closure.
  5. Guest Igor
    #9 Guest Igor Guests July 15, 2018 12:14
    2
    It’s probably in England microwaves are thrown into garbage cans. We have housekeeping people and will always find application for details from her.
  6. Nnm
    #10 Nnm Guests August 2, 2018 12:39
    2
    immerse it in oil
    1. Guest Yuri
      #11 Guest Yuri Guests February 13, 2019 2:57 p.m.
      2
      That would burn hotter!
  7. Vyacheslav
    #12 Vyacheslav Guests March 19, 2019 1:26 p.m.
    0
    Tell me, can this transformer be used as an output in a VLF tube? I do not know the ratio of the turns, but based on the gain, it is very similar if you turn it around.
  8. Nikita K
    #13 Nikita K Guests March 23, 2019 09:09 a.m.
    1
    transformer iron is mb and not bad, but it seems to me that welding spoils everything, induction currents inductance do not go in a circle and are quenched at the seam, therefore the efficiency is small!
  9. Edward
    #14 Edward Guests May 21, 2019 23:03
    2
    such a transformer is not suitable as a power supply unit! it has a large open-circuit current. and its dimensions are similar to that of 500 W and its power is boosted to 1200 W, therefore it is not designed for a long-term operation mode. It also heats up even without load. spot welding twists of wires or a small welding machine and then with intensive forced ventilation
  10. Basil
    #15 Basil Guests July 21, 2019 09:58
    0
    But I didn’t do anything. I just connected the high-voltage winding to 220v.
    At the output, I got about 20v change.

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