The Three-phase Generator Principle

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We have a nice three phase power supply in our home, but where does it come from? And why does the waveform has a sine shape?

Michael Faraday discovered the electromagnetic induction. When you place a conductor in a varying magnetic field a voltage is induced by the EMF (electromagnetic force).
This principle is used in generators.
Click on START to run the generator animation.

In our simplified example the generator consists of a rotating magnet (rotor) and of a stator with six conductor coils (A, A’, B, B’, C, C’). Between A, B and C is a shift of 120°. The conductors with an apostrophe are on the opposite side.

If the rotor N (north-pole) is matching with the stator A, we have maximum voltage amplitude in phase A (L1). When the rotor N reaches the A’, we have the minimum amplitude.
This happens for all three phases. The sine waves are coming from the increase or decrease of the EMF on a single conductor. Monitor the wave generation in relation to the rotor position.

The rotating speed of the rotor gives us the frequency. When we want to have 50 Hz, the rotor has 50 revolutions per second.
In praxis it’s not a static magnet. The electromagnetic force can be controlled much better when using an electromagnet.
Our portable test equipment (e.g. RS350) has many possibilities to check the power quality, e.g. total harmonic distortion.

This post is to refresh the knowledge. We need this for the following articles.
Thank you for reading.

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