View Full Version : Number of Poles
2007-07-17, 03:03 AM
A property of an electrical connector is 'No. of Poles'. What does this actually mean? I note that you can only add a number between 1 and 3. This would indicate to me it is the number of phases.
(This is from a non-electrical person)
2007-07-17, 12:02 PM
No. of Poles does not always equal No. of Phases:
120V, 1 Phase = 1 Pole
208V, 1 Phase = 2 Poles
208V, 3 Phase = 3 Poles
240V, 1 Phase = 2 Poles
240V, 3 Phase = 3 Poles
277V, 1 Phase = 1 Pole
480V, 1 Phase (rare) = 2 Poles
480V, 3 Phase = 3 Poles
2007-07-22, 11:16 PM
Not an electrical person either, so the attached illustration may help ?
2007-07-23, 12:45 PM
Here is a good picture to represent it.
The three lines (red, black and blue) represent the three phases of a power system. They are all 120 degrees out of phase, representing three windings on a generator in a circular formation.
For a 208Y/120V system, if you take the peak of the wave (120V) to ground (0V) you will get a voltage of 120V.
However, if you take the voltage from phase Red to phase Black (voltage is the difference is potential) you will always have the line-to-ground voltage*sqrt(3) = 208V. If you actually try to visualize the wave, you will see that the difference between any two phases will always be a larger amplitude sine wave then that to ground.
If you are just trying to get straight 208V from one phase to another it is called single phase and as such requires 2 poles.
Three phase requires three poles because you are using all three phases.
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