Excitation (magnetic) facts for kids
Excitation is a process to create a magnetic field from electric current. This process is used in electric machines (generators or motors) whose rotor spins in a magnetic field. This magnetic field can come from a permanent magnet or field coils. In the case of electric machine with field coils, a current must flow to the coil to generate the magnetic field, so that the field coils can act as a "magnet", like in the case of electric machine with permanent magnet. The device in which excitation happens is called the exciter.
Images for kids
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A 100 kVA direct-driven power station AC alternator with a separate belt-driven exciter generator, date c. 1917.
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A self-excited shunt-wound DC generator is shown on the left, and a magneto DC generator with permanent field magnets is shown on the right. The shunt-wound generator output varies with the current draw, while the magneto output is steady regardless of load variations.
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A separately-excited DC generator with bipolar field magnets. Separately-excited generators like this are commonly used for large-scale power transmission plants. The smaller generator can be either a magneto with permanent field magnets or another self-excited generator.
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A field coil may be connected in shunt, in series, or in compound with the armature of a DC machine (motor or generator).
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Alternator of 1930s diesel generating set, with excitation dynamo above
