Number of winding layers
The number of layers indicates the number of different coils in a slot.
Integer-slot windings without any shortening of the coil pitch are single-layer windings. When the coil pitch is shortened, some slots can contain two different phases and consequently require two layers. The slot is usually divided horizontally.
Fractional-slot windings with a number of slots per pole per phase over 1 generally require 2 layers. The slot is usually divided horizontally.
For concentrated windings, single-layer windings have coils wound only on alternate teeth (i.e., on every second tooth), whereas each tooth of the double-layer windings carries a coil. The slot is usually divided vertically, cf. Fig. 1.
Fig. 1 Three teeth and the coils of a concentrated winding: a) Single-layer winding, b) Double-layer winding.
For examples of actual winding layouts, please visit the glossary pages of integer-slot windings, fractional-slot windings, or concentrated windings.
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