How to design a ferrite core toroidal transformer

Written by david sandoval
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How to design a ferrite core toroidal transformer
Learn how to design a ferrite core toroidal transformer. (Jelena83/iStock/Getty Images)

Ferrite-core transformers are often used to minimise power losses due to a phenomenon called hysteresis. Toroidal transformers are also used to minimise power losses. A ferrite-core toroidal transformer combines the benefits of both transformer types. Because transformers are used for one of three purposes -- to isolate DC electrical energy from one side of an electrical circuit, step an AC signal voltage up, or step an AC signal down -- it is important to determine how the transformer will be used before attempting to wire it up.

Skill level:

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Things you need

  • Calculator
  • Pen or pencil
  • Paper
  • Ferrite or iron ring
  • Insulated electrical wire
  • Permanent marker
  • Measuring tape

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  1. 1

    Determine how the transformer will be used. This step will determine how the transformer is wired.

  2. 2

    If the transformer will be used as either a step-up or step-down transformer, determine the multiplication ratio for transformer and write this factor down. For example, if you intend to build a step-up transformer that will convert a six-volt AC input signal into a 12-volt AC output signal, write down that you intend to build a "2:1 transformer." If you intend to build an isolation transformer, write down that you intend to build a "1:1" transformer.

  3. 3

    Wind the wire around the ferrite or iron ring so that the wire makes one tight loop around the ring. Mark the wire's insulation where the wire begins to loop. Mark the end of the wire loop as well. Unwrap and straighten the wire out.

  4. 4

    Measure the distance between the markings on the wire, and write down the measurement. This distance will determine how many wire turns can be made on this transformer core.

  5. 5

    Calculate how many wire turns are required to fabricate the transformer. For example, if you wish to make a 2:1 step-up transformer with 10 wire turns on the output side, you will need to have enough wire to complete 30 wire turns -- 20 for the input side, and 10 for the output side.

  6. 6

    Calculate the total wire length you will need for each transformer side by adding four inches to the wire lengths you previously calculated. For example, if a transformer input side with 20 wire turns requires one foot of wire, the total wire input wire length should be one foot and four inches.

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