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How does the rectification of alternating current in a generator actually work? When alternating current is rectified, the alternating current is sent through diodes. Diodes only allow current to flow in one direction. This means that only half of a phase of the alternating voltage can pass through the diode at a time. If you rectify an alternating voltage with a simple rectifier, i.e. a single diode, the lower curve is essentially cut off. You no longer have a change in polarity. However, half a phase is missing. If you now use 2 diodes, as with a three-phase generator, you can gain the missing half a phase. Figuratively speaking, half the sine curve is folded upwards. Now there are only the positive voltage components. The current only flows in one direction. In order to obtain as even a voltage as possible, three coils are used in the vehicle generator. The coils are offset by 120°. The alternating voltage is correspondingly phase-shifted by 120°. Each phase is rectified with 2 diodes. All negative voltages are, figuratively speaking, folded upwards. This creates a more even voltage than with just one coil. However, the consumers in the vehicle are designed to compensate for the small fluctuations.