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BASICS OF ELECTRICITY - 2

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GENERATION OPERATION FROM 90 TO 180 DEGREES:

The armature continues to rotate from 90 to 180 degrees,cutting less lines of flux. The induced voltage decreases froma maximum positive value to zero.

GENERATION OPERATION FROM 180 TO 270 DEGREES:

The armature continues to rotate from 180 degrees to 270degrees. The conductors cut more and more lines of flux, butin the opposite direction. Voltage is induced in the negativedirection building up to a maximum at 270 degrees.

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GENERATION OPERATION FROM 270 TO 360 DEGREES:

The armature continues to rotate from 270 to 360 degrees.Induced voltage decreases from a maximum negative valueto zero. This completes one cycle. The armature will continueto rotate at a constant speed. The cycle will continuouslyrepeat as long as the armature rotates.

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FREQUENCY:

The number of cycles per second made by voltage induced in the armature is the frequency of the generator. If the armature rotates at a speed of 60 revolutions per second, the generated voltage will be 60 cycles per second. The accepted term for cycles per second is hertz. The standard frequency in theUnited States is 60 hertz. The following illustration shows 15 cycles in 1/4 second which is equivalent to 60 cycles in onesecond.

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FOUR POLE AC GENERATOR:

The frequency is the same as the number of rotations per second if the magnetic field is produced by only two poles.An increase in the number of poles, would cause an increase in the number of cycles completed in a revolution. A two-pole generator would complete one cycle per revolution and a four-pole generator would complete two cycles per revolution.An ACgenerator produces one cycle per revolution for each pair of poles.

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VOLTAGE AND CURRENT:

PEAK VALUE:

The sine wave illustrates how voltage and current in an AC circuit rises and falls with time. The peak value of a sine wave occurs twice each cycle, once at the positive maximum value and once at the negative maximum value.

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PEAK TO PEAK VALUE:

The value of the voltage or current between the peak positiveand peak negative values is called the peak-to-peak value.

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INSTANTANEOUS VALUE:

The instantaneous value is the value at any one particulartime. It can be in the range of anywhere from zero to thepeak value.

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