Three-phase asynchronous motor with single-layer winding

A single-layer winding is one in which only one coil side is embedded in each stator slot, so the total number of coils is only half the total number of motor slots. The advantages of a single-layer winding are that it has fewer coils and is simpler to manufacture; it has no interlayer insulation, so the slot utilization rate is higher; and single-layer structures do not experience inter-phase breakdown failures. The disadvantages are that the electromagnetic waveform generated by the winding is not ideal, the motor's iron loss and noise are both larger, and the starting performance is slightly worse, so single-layer windings are generally only used in small-capacity asynchronous motors. According to the shape of the coils and the arrangement of the end connection parts, single-layer windings can be divided into several winding forms, such as chain windings, cross-chain windings, concentric windings, and cross-concentric windings.
1. Chain Winding
Three-Phase Asynchronous Motor
Three-Phase Asynchronous Motor [8]
Chain windings are composed of single-layer coil elements with the same shape and width, and are so named because the coil ends are like interlocking rings. A particularly important point for single-layer chain windings is that the coil pitch must be an odd number; otherwise, the winding cannot be arranged.
2. Cross-Chain Winding
When the number of slots per pole per phase (q) is an odd number greater than 2, a chain winding cannot be arranged, in which case a cross winding with single and double coils must be used.
3. Concentric Winding
In a concentric winding, all coils within the same pole and phase group enclose the same center.
4. Cross-Concentric Winding
When the number of slots per pole per phase (Q) is an even number greater than 2, a concentric winding can be used.
The advantages of single-layer concentric windings and cross-concentric windings are that winding and embedding the coils are relatively simple. The disadvantages are that the coil ends are too long and consume too much wire. Except for occasional use in small-capacity 2-pole and 4-pole motors, this type of winding is rarely used now.