What is the principle of a transformer

Electricity knowledge: what does a transformer actually do?

The transformer: definition and origin.

The word transformer is derived from the Latin “transformare” and means to transform or transform. It is also affectionately referred to as a "transformer" by fans and users. Synonymous are transformer or transformer. Since its invention by Lucien Gaulard and John Dixon Gibbs (London) in 1881, the transformer has spread and can now be found all over the world.

What is a transformer?

The transformer is a technical system of energy technology. The component consists of coils, copper wire and core: the multi-wound wires are immediately noticeable; they are a bit reminiscent of coiled sewing thread. In most applications, the task of the transformer is to increase or decrease electrical voltages. Transformers convert an incoming alternating voltage a in a certain ratio (e.g. 20 to 1, that depends on the coil windings) into an outgoing alternating voltage b. So that's what a transformer does: it transforms AC voltages (not DC voltages). Transformers are hidden in small, free-standing buildings or in the small rooms of large buildings: The transformer is relatively shy and not entirely harmless when it is live. A transformer can give you a huge electric shock if you get too close without warning or precautions. That's why he wants to keep most people away with the following label:

The transformer only allows selected people to visit. Then it can also be that he can switch off properly and all the tension of everyday life falls away from him.

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Different transformers.

The transformer is available in a wide variety of sizes, designs and colors. Many electrical devices or electricity consumers in our household have a small transformer, as the required operating voltage often differs from the mains voltage. There are chargers for cameras, smartphones, tablets and laptops in every household - there are transformers in every single one.

The big brother of the device transformer, on the other hand, is used for power distribution in industry and by power grid operators. It is called a distribution transformer. In its largest form, the transformer lives in the substation. There it is the link between the voltage levels of the power grids. It is also called a network transformer or transformer.


The capabilities and inner values ​​of the transformer.

The main area of ​​application for transformers is to increase or decrease alternating voltages. What enables the transformer to convert voltages? In order to be able to answer this question, we have to dive deeply into the field of electrical engineering. If this is too technical for you, you can skip the following paragraph.

The principle of operation of the transformer is based on the law of induction. In terms of construction, the transformer usually consists of a ferrite or iron core and electrical conductors that are wrapped around this core several times. It basically has an input side or primary side and an output side or secondary side. The windings are called the primary and secondary coils. There is also a sketch of the transformer for illustrated reflection:




An alternating voltage applied to the primary side causes an alternating magnetic flux in the iron core of the transformer in accordance with the law of induction. This means that a magnetic field is created that cyclically changes its polarity due to the applied alternating voltage. The changing magnetic flux in turn induces a voltage on the secondary side of the transformer.

What is a turns ratio?

If the number of copper windings on the primary and secondary side is the same, the voltage on both sides of the transformer is the same (in no-load case, i.e. without load). In this case the so-called "winding ratio" is equal to one. If the winding ratio is different, the voltage on the secondary side of the transformer changes. It therefore transforms the voltage on the input side to a defined voltage level on its output side. This is called stress transformation.

Alternating Current and Ampere's Law.

If an electrical consumer is now connected to the secondary side of the transformer, an alternating current flows in the secondary winding. So electricity is drawn. According to Ampère’s law, this current also causes an alternating current in the primary winding. The current strength in turn depends on the winding ratio. One speaks here of a current transformation.


Transformers explained briefly and clearly: in the video from the VDI (Association of German Engineers).

The transformer in today's energy technology.

Transformers are indispensable for the power supply, as electrical energy can only be transported economically over long distances using high-voltage lines. As you already know, the public power grid has different voltage levels. Large power plants operate with high voltages, whereas we at home operate with relatively low voltages. The link between these voltage levels is the transformer.

The transformer converts high voltage into low voltage - or vice versa.

A transformer is used to feed electrical energy from a higher voltage power grid into a lower voltage power grid. Since the transformer is a tolerant guy, it also works in the opposite direction. You can also feed generated electricity back into a higher voltage level via a transformer.

Physically or mathematically, voltages and windings are calculated using the formula: U1: U2 = N1: N2 (voltage ratio for an ideal transformer). U1: voltage in volts at the first coil; U2: voltage in volts at the second coil; N1: number of turns of the first coil; N2: number of turns of the second coil.

Oh, galvanic isolation.

The transformer gets a big plus point for its technical possibility for "galvanic separation" of electrical circuits. That sounds rather sad, but it isn't.

Galvanic isolation rather means that two circuits are not connected to one another via an electrical conductor. The energy transfer takes place here exclusively by induction in the magnetic field of the transformer core.

This offers every user increased safety, even if he is freed from any knowledge of the dangers of electrical current. If there is a short circuit in the device, the resulting fault current can flow through the human body upon contact with the device. That can life threatening be. If a transformer with galvanic isolation is used, this fault current remains very low and relatively harmless.

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Sketch transformer: Wikipedia.