Advice 1: How to determine primary winding of the transformer

Power transformers are used as sources of alternating voltage in different equipment. In the manufacture of improvised devices, there arises the need for selecting transformer with appropriate parameters. Before measuring the output voltage you must find the primary winding, to enable the transformer to the network.
How to determine primary winding of the transformer
You will need
  • - A powerful electric lamp in a cartridge;
  • - multimeter.
Instruction
1
Carefully inspect the transformer. On some models of transformer windings are signed on the upper layer of insulating paper and signed the appropriate conclusions. TPP transformers are completely encapsulated green color, they are called military transformermi. They write a brand that's in the book on such a transformerm, and number the terminals of the windings. To find the primary winding of the transformer from the amplifier or the low-voltage power supply is quite simple – it is made of wire of smaller cross section than the secondary winding. To find the primary winding of the low-power transformer from the devices it is possible, having measured resistance of all windings. The winding with the highest resistance will be the primary.
2
On old tube equipment used the powerful multiple-winding transformers of THANE. Resistance their high-voltage windings differed slightly, and the value of the winding resistance was not difficult to determine which winding is the primary. You can find the primary winding of such transformer, measure the resistance of each winding and take note of the numbers on paper, check also the location of their conclusions. Those windings, the resistance of which tends to zero is a low voltage winding, designed to supply filament cathodes of radio tubes. The remaining coil can be investigated by submitting them to stress.
3
Plug in a powerful electric lamp for 220V in series with the winding of the investigated transformer and switch in the network received an electrical circuit. Using a multimeter switched to the measuring AC voltage, measure the voltage on the winding of the transformer. After that, turn the power off and explore the other winding. Record the results on paper. In the study of the windings be careful and never turn winding with included mains supply. When a voltage is applied to the coil do not touch the conclusions of the other windings, as they are induced corresponding voltage.
4
Make the power cable to the fuse holder, install the fuse at a current of 1A.
5
For this record to locate the coil, which was the highest supply voltage. Turn on the transformer, this winding network by connecting sequentially the multimeter switched to the current measurement. If no load current is less than 30-50mA for transformers with a power of 200-300W may, the primary winding was found correctly.
6
Disconnect mains supply, disconnect the multimeter from the test winding, switch mode Vollmer. Measure the voltage and record the value obtained on paper.
7
Measure the voltage on the windings of the cathode was found. If the network voltage is 220-225V it is from 6.25 to 6.35 In, so studied winding is the primary.

Advice 2: How to calculate winding of the transformer

In Amateur practice, it is frequently necessary to fabricate a transformer with non-standard values of current and voltage. Well, when it is possible to find ready-made device with the required windings, in another case to make it have their own.
How to calculate winding of the transformer
Instruction
1
Decide before you start the calculation with the output of the future device. The transformer consists of a magnetic core (core), primary (mains) and secondary windings. An important feature in the calculation of the transformer is the choice of the core. The best option is the core armor type that, in contrast to the toroidal, it will need half as much wire for the manufacture of the windings. When choosing a core, refer to the set thickness and width of the Central plate. The cross-sectional area define as the product of the thickness set to the width of the plate.
2
Calculate the number of turns of the coil (ω) by 1 volt. It is calculated by the formula: ω = S:50, where S is the cross-sectional area of magnetic core in square centimeters. To do this, measure the cross-sectional area of the core, based on take that 50 square centimeters = 1 coil per volt. For example, if the cross-section of the magnetic circuit equal to 150 square centimeters, then 1 volt (150:50) need 3 turns of wire.
3
Calculate the primary (network) winding for voltages of 220 volts. Obtained in paragraph (2) multiply the value by 220. Example: 3х220=660 turns of the primary (network) winding.
4
Calculate the secondary winding based on the needs. Obtained in paragraph (2) multiply the value to the desired voltage. Assume that the output voltage must be 80 volts, then 3х80=240 turns of the secondary winding. Thus, for a step-down transformer with input voltage of 220 volts and an output voltage of 80 volts, you need 660 turns of the primary (network) winding 240 turns of the secondary winding of insulated wire with a cross section of 2 square millimetres.
5
Check at the end of the calculation, the fill factor of the window windings. It should not exceed 0.5, and only then can you start winding, otherwise you'll have to take the core, which has a greater cross-sectional area, and redo all the calculations. Don't forget to consider the thickness of the insulation. Calculation step-up transformer to produce a similar way.

Advice 3: How to determine primary and secondary winding

While Amateur construction is often used transformers with unknown parameters. In this case, there is a need to determine winding of the transformer and their characteristics, in particular, the number of turns.
How to determine primary and secondary winding
Instruction
1
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.
2
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.
3
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.
4
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.
5
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.
6
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.

Advice 4: How to determine primary winding

Is the primary winding of the transformer, which is supplied with alternating voltage from the outside. The other winding, whose voltage is supplied to the consumers are called secondary. To determine which of the windings is intended for use as a primary, it is possible experimentally.
How to determine primary winding
Instruction
1
If it is known that the transformer is decreasing and is powered from the mains, using an ohmmeter, measure the resistance of each winding. One of them, it is much more than the rest - it is primary. When measuring do not touch the terminals of the transformer and probe - despite the fact that it's not plugged in, measuring voltage is small, the amplitude of the bursts of self-inductance can be big enough for a painful electric shock.
2
At the anode, combined anode-filament transformer secondary winding can be both lowering and increasing, so take advantage of the above-described criterion will not work. To find the primary coil in this case on circumstantial evidence. For example, its findings can be located separately from the insights of others. If you can see where it is sent to the conductors extending from the pins to the windings themselves, often find among them primary one can, knowing that most often it is wound first (i.e., it is located closest to the middle of the frame).
3
Modern transformers often have a partitioned frames. In this case the primary winding is usually placed in a separate section. This section can be wrapped with red tape, and the presence of the insulation layer thickening (thermal fuse) is a good indication that the winding is the primary.
4
Most transformers designed for operation at a frequency of 50 Hz, the number of turns per volt are close to 10. Wrap it in a temporary additional winding and feed her alternating voltage with the same frequency and with the current value in 1 V. caution measure the voltage on the other windings, the primary can be considered the voltage which is close to 220 V. Then remove the additional winding.
5
If the primary winding has a tap, it can operate on two voltages: 127 and 220 V. In the second case, the inclusion of it completely. If there are two separate windings (127 and 93 a), include them in series (voltage 220V) only common mode. To do this, in the previous experiment, try to include them consistently in two ways (before you switch the voltage from the auxiliary winding remove). The variant in which the resulting voltage will be much greater and corresponds to in-phase switching.
Note
Do not work under tension.
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