Number Of Slots Per Pole Per Phase Formula
A basic single-phase motor usually has four slots that contain two pairs of coil windings, each offset by 90 degrees; a basic three-phase motor has six slots with three pairs of coil windings, each pair offset by 120 degrees. To complicate matters, multiples of pole pairs can be utilized to increase the corresponding number of slots. The number of slots per pole per phase will be 3 (18/2)/3 = 3. This means that a particular phase will consists of three coils distributed in three slots under a single pole. This is shown in figure below. In the above figure it can be seen that, coils are distributed in slot number 1,2,3 and 10,11,12.
In Emetor, a winding is called fractional-slot winding when the number of slots per pole per phase is fractional and superior to 1.
In the Emetor winding calculator, fractional slot windings with a number of slots per pole per phase strictly superior to 1 are indicated with orange cells. In Emetor, only fractional slot windings with a number of layers equal to two are represented. Below is the example of the layout of a 2-pole 9-slot fractional slot winding which has a number of slots per pole per phase equal to 1.5:
| A | c | c | B | a | a | C | b | b | ||||||||||||||||||
| A | A | c | B | B | a | C | C | b |
Fig. 1 Double-layer 2-pole 9-slot fractional slot winding with a winding factor of 0.945.
Number Of Slots Per Pole Per Phase Formula Sheet
Concentrated windings are also fractional slot windings, but they have a number of slots per pole per phase strictly inferior to 1.
Number Of Slots Per Pole Per Phase Formula Calculator
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