what are two ways in which an AC alternators field windings be excited?
2006-12-17 14:41:16 · 5 answers · asked by Anthony L 1 in Science & Mathematics ➔ Engineering
Self -excited and separately-excited alternators are the common methods. DC machines are excited similarly.
In an emergency power generator where no initial power is available to excite the rotor of the alternator, excitation comes from residual magnetism in the rotor. This small amount of magnetism produces a small AC voltage at the stator that is rectified and fed back to the rotor as DC for more output and the cycle continues until full output is reached. This system is also used in some US automobiles.
Separate-excitation is when an external battery is used to supply excitation voltage to the rotor for initial operation.
Both systems use regulator circuitry to provide constant voltage or variable current output depending on the application.
2006-12-17 15:21:45 · answer #1 · answered by Buffertest 3 · 1⤊ 0⤋
You can use separate excitation where you use a small DC generator turned by the shaft of the alternator to supply DC field excitation through an appropriate regulator.
Or self excitation where an portion of the output of the alternator is rectified to supply DC field excitation through an appropriate regulator.
2006-12-17 16:27:04 · answer #2 · answered by charley128 5 · 0⤊ 0⤋
You can wire them in parallel with the output from the generator or in series with the generator.
The parallel arrangement is called a "dynamo": a little residual magnetic field makes a little voltage which drives current through the field winding and more magnetism is produced ... it sort of boot-straps itself.
The series arrangement makes the field sensitive to the current being drawn by the load. A higher current produces greater magnetism.
You can use the two arrangements together to tailor the properties of your generator.
2006-12-17 15:13:01 · answer #3 · answered by Anonymous · 1⤊ 0⤋
excited? err..you mean increase current output? i'm lost..but if so..either spin it faster..or increase the magnetic field by increasing field...or passing more current though the field windings
allow for a current to pass through the field windings
2006-12-17 14:50:37 · answer #4 · answered by Dan 2 · 0⤊ 1⤋
with a static magnetic field from permanent magnets, or with a burst of electricity, frequently from a capacitor
2006-12-17 14:48:52 · answer #5 · answered by rboatright 3 · 0⤊ 1⤋