When using double-layer winding, short distance (when the windings are stacked) or reducing the connection between coil groups (when the windings are wavy) can save the copper consumption at the end. More importantly, both distribution and short distance can be used to improve the waveforms of winding electromotive force and magnetomotive force.

Advantages: 1, all coils have the same pitch, and winding is convenient; 2, the end of the coil has little deformation and is easy to form;

Disadvantages: 1, the number of coils is twice that of single-layer winding, and it is laborious to embed wires; 2. Because the out-of-phase coil edges are embedded in the same slot, short circuit fault is easy to occur; 3. Insulation should be added between the layers, and the slot full rate will be lower.