A transformer converts voltage or power

Transformer / transformers / transformer

A transformer is used to step up or step down voltages, currents and resistances in an AC circuit. So increased or decreased.
The transformer, or transformer for short, acts on the input or primary side like a consumer R for its AC voltage source, provided the transformer is loaded with nominal load. When unloaded, the transformer acts like an inductance. The output side or secondary side acts as an alternating voltage source with source voltage U.0 and internal resistance Ri.

The transformer basically consists of two coils lying next to each other with the same or different number of turns. A turn is when the wire is looped around the bobbin. The entirety of the turns is called the winding. A changing magnetic field is generated on the input winding by the applied alternating voltage. An induction voltage is generated on the output winding. The level of this voltage depends on the turns ratio of the primary and secondary side of the transformer.

Primary sideSecondary side
60050 V60050 V
60050 V1200100 V
60050 V30025 V

N = number of turns / U = voltage

If the number of turns on the primary side is greater than on the secondary side, then the output voltage is less than the input voltage. If the number of turns on the secondary side is greater than that on the primary side, then the output voltage is greater than the input voltage.

Isolation transformer and transformer

Isolation transformers are used to galvanically isolate the alternating voltage from the power grid. You should separate two circuits from each other for safety reasons. Transmitters are used for data transmission and in measurement and control technology for audio frequency transmission.

Ratio of voltage and current

The relationship between voltage and current is inversely proportional to each other.

A change in the voltage at the input leads to a change in the maximum current that can be drawn at the output (secondary side) of the transformer.
If the voltage is stepped down, the current that can be drawn increases. If the voltage is stepped up, the current that can be drawn decreases.
A higher voltage at the output leads to a lower current at the input. A lower voltage at the output enables a greater current draw.

Circuit symbol (secondary side with one winding)

Circuit symbol (secondary side with two windings)

Toroidal transformers

Toroidal transformers consist of a toroidal iron core around which the primary and secondary coils are wound. Toroidal transformers are lightweight, require little space, are more efficient and have a lower magnetic stray field. This gives you decisive advantages over rectangular transformers. The high switch-on pulses are a disadvantage.

Rectangular iron core transformers

Rectangular transformers are very common. Especially in power supplies and integrated power supplies. The power consumption there is not too high. A plug-in power supply unit can or must even be dispensed with. The weight of the iron core is often uncomfortable and is a significant part of the weight of an electronic device.
It can be assumed that the iron core causes 10% energy loss during the transformation. To compensate for this, 10% more turns are simply wound. This ensures the desired tension ratio.

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