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Fun Facts in Science and Technology

Electrotechnical facts simply explained


Many people still know the various definitions from their studies or training, which were always explained so in such a boring and dry way. But there is another way, as you can see in our picture, and so the reactive power and the active power get a completely different meaning and above all, you certainly won't forget that anymore.

Reactive power, active power and apparent power are terms used in electrical engineering and refer in an electrical power supply network to the energy transmitted from the producer to the consumer.

Active power is the energy that actually works and can be converted into another form of energy, such as kinetic energy, heat or light. If one takes the popular example of a beer glass including a foam crown, the active energy, i.e. the actual power, corresponds to beer without a foam crown. This active energy is then converted into per mille. The active power is therefore the power that is actually consumed and with which the active energy is carried out.

The reactive power is the power required to build up magnetic fields in transformers, generators and electric motors or to charge capacitors. This reactive energy is contained in the transformers and capacitors and is needed to transfer the active power. It can be said that reactive power is generally undesirable because it cannot be converted into energy/power (such as movement, heat or, as in our beer example above, per mille) and additionally loads the grid. Explained using the example of beer with a foam crown, the foam crown corresponds to the reactive power. Despite everything, the reactive power is physically necessary in order to transmit active power in the alternating current system at all.

The apparent power now results from both, the active power and the reactive power and corresponds in our example to the complete beer.

However, there is still a problem, because you cannot simply add active power and reactive power. The apparent power corresponds to the geometric sum of active power and reactive power: This means that the root is taken from the sum of active power to the square plus reactive power to the square. Then the apparent power is calculated. And anyone who solves this arithmetic problem has earned the pleasure of beer!