Monday, June 27, 2011
2:17 PM | Posted by
Anonymous |
when we speak about the generator speed we have to speak about two important factors.first factor is Rotor poles
Rotor Poles
Increasing the number of magnetic poles on the rotor enables rotor speeds to be slower and still maintain the same electrical output frequency. Generators that require slower rotor speeds to operate properly use multiple-pole rotors.
For example, hydropower plants use generators with multiple-pole rotors because the prime mover (i.e., water) is very dense and harder to control than light-weight steam.
The relationship between the number of poles on the rotor and the speed of the shaft is determined using the following mathematical formula:
Rotor speed (RPM) = 7200/ Number of poles
Above figure shows the concept of multiple poles in a generator rotor. Since these poles are derived from electromagnets, having multiple windings on a rotor can provide multiple poles.
Second Factor is the output frequency.the following relationship determines the relation between the frequency and speed
Frequency = (no. of poles * Rotor speed)/120 (HZ)
Do you feel confused confused about this lesson? Leave your question now in a comment.
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