In practice Amateur design usually has to deal with raising and lowering transformers. At the core of these transformers, make electrical steel, is wound the required number of windings. The number of windings and number of turns they have been selected in order to output the desired voltage.
Regardless of the type of the transformer primary is the winding that is energized. Secondary – TA, to which a load is connected. The primary winding is wound first, followed by the isolates. On top of these is wound the secondary winding.
In many transformers the findings indicated labels that helps you identify the windings. If no labels, a multimeter (tester) to locate the paired ends of the windings and note the resistance. Please note the withdrawal on top of it – it will almost certainly belong to the secondary winding. If the step-down transformer, the secondary winding resistance is always less than the primary. Compare resistance of windings is found – if the external resistance is less than the internal, this step-down transformer and you have successfully identified the windings.
If the transformer is not four, and more, and when checking the tester, you find 3-4 more related insights, you are dealing with a secondary winding having an intermediate conclusions for obtaining different voltages. Network (primary) in this case will be a coil with two terminals and the largest resistance.
To help identify the windings can diameter of the wire used – it is thicker than the secondary than the primary. This is due to the fact that the transformation of the voltage is accompanied by an increase in current strength.
If you want to know the number of turns in the windings, wrap the last coil on top of another 30-50 turns. Then feed the primary winding of a small voltage, e.g. 12 V. Measure the voltage in the secondary, and additional windings. To calculate the number of turns use the formula: n = Un × Wдоб / Uдоб, where n is the number of windings of the transformer, Un – existing on this winding tension, Wдоб – number of turns in the winding extension, Uдоб – voltage on it.