Compared with single-layer windings, single-layer and double-layer windings have the advantages of better magnetic field waveforms, starting performance and lower stray losses. Compared with double-layer windings, single-layer and double-layer windings can achieve a larger effective span when the actual coil span is shorter, significantly increasing the fundamental coefficient. This effect is particularly remarkable in 2-pole motors. If both have the same theoretical span, the amount of wire used at the end can be reduced and the stator resistance can be lowered, achieving a dual effect of copper conservation and energy saving. By fully leveraging the advantages of single and double-layer windings in the design, the efficiency and other performance indicators of the motor can be enhanced, and the temperature rise of the motor windings can also be reduced.

(1) For 2-pole and 4-pole motors with a center height of 160mm or less, single-layer windings are generally used. After switching to single or double-layer windings, the magnetic field waveform can be improved, the stray loss can be reduced, the average length at the end can be shortened, which can increase the motor efficiency, lower the temperature rise, improve the starting performance, and also reduce the amount of copper wire used.

(2) For 2-pole motors with a center height of 180mm or less, which are generally double-layer windings, changing to single or double-layer windings can increase the fundamental winding coefficient by about 15%, that is, the actual number of turns can be reduced by about 15%. Under the condition of ensuring the same effective number of turns, the actual number of turns can be reduced. When maintaining the same slot fullness rate, the cross-sectional area of the wire can be increased, thereby reducing the stator resistance and the same loss of the stator, and improving the efficiency of the motor. Due to the requirements of the off-line process, the original double-layer winding of the 2-pole motor adopted a 2/3 short pitch. The excessive short pitch made the magnetic field waveform very poor. After adopting the appropriate form of single and double-layer winding, the magnetic field waveform was improved, and the stray loss could be reduced, the efficiency could be increased, the temperature rise could be reduced, and the starting performance could be improved. Both of the above two major factors enhance efficiency and achieve energy-saving effects.

(3) For 4-pole motors with a center height of 180mm or more, if the winding is changed from double-layer to single or double-layer, the actual average span can be shortened, the average half-turn length can be reduced, the stator resistance can be decreased, the stator loss can be reduced, and the efficiency of the motor can be improved.

Another feature of single and double-layer windings is that the selection of the number of turns per slot is relatively flexible. It is feasible to add or remove one turn from a single or double-layer winding, but this is more difficult to do in both single-layer and double-layer windings. When single or double-layer windings are adopted, a more reasonable number of series turns per pole and per phase can be selected, and a more reasonable electromagnetic design scheme can be obtained.

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