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Detailed explanation of motor winding classification

source：未知 time：2024-08-28 13:36nbsp; click：

According to the different arrangements of the winding coil elements in the slots, the motor windings can be divided into single-layer windings, double-layer windings and single- and double-layer mixed windings. The details are as follows:

1. Single-layer windings

Definition: A winding with only one effective coil side embedded in each stator slot, and the total number of coils is half of the total number of slots in the motor.

Advantages: a. The winding has fewer coils and the process is relatively simple. b. There is no interlayer insulation, so the slot utilization rate is high. c. The single-layer structure will not have interphase breakdown failure.

Disadvantages: The electromagnetic waveform generated by the winding is not ideal, the iron loss and noise of the motor are large, and the starting performance is slightly poor.

Application range: Generally only used in small-capacity asynchronous motors.

Classification:

a. Chain winding: It is composed of single-layer coil elements with the same shape and width. The characteristic is that the winding coil is one ring inside another, shaped like a long chain. It is mainly used in small three-phase asynchronous motors with the number of slots per pole and phase. The advantages are that the coils are of the same size, easy to manufacture, and the coils can be short-distance with shorter ends. Special attention should be paid to the single-layer chain winding that its coil pitch must be an odd number, otherwise the winding will not be able to be arranged.

b. Cross-chain winding: The arrangement method of cross-chain winding is the same as that of chain winding, but the number of coils in the pole-phase group is not equal and the pitch of the coils is not equal. When the number of slots per pole per phase is an odd number greater than 2, the chain winding cannot be arranged. At this time, a cross-chain winding with single or double coils is required.

c. Concentric winding: This winding is composed of large and small coils with unequal pitches in the same pole-phase group. It is named because all coils in the pole-phase group embrace the same center of the circle. It is mainly used in 2-pole asynchronous motors. It is convenient to put the wire down. The ends of the two groups of coils in the same phase are staggered, the overlapping layer is small, it is easy to arrange, and the heat dissipation is better.

d. Cross-concentric winding: When the number of slots per pole per phase is an even number greater than 2, the cross-concentric winding is adopted. The advantage is that the winding and embedding of the winding are relatively simple, and the disadvantage is that the coil ends are too long and consume too much wire. It is occasionally used in small-capacity 2-pole and 4-pole motors, but it is rarely used at present.

2. Double-layer winding

Definition: Two coil element sides are embedded in each slot. When one coil side of the coil element is embedded in the lower layer of a slot, the other coil side is placed in the upper layer of another slot. The number of coils is exactly equal to the number of slots.

Advantages: a. The most favorable pitch can be selected, and distributed winding can be used at the same time to improve the waveform of electromotive force and magnetomotive force. b. Fractional slot winding can be used to weaken high-order harmonics. c. The electromagnetic performance, force energy index and starting characteristics of the motor are better than those of single-layer windings. d. All coils have the same pitch, which is convenient for winding. e. The coil end has little deformation and is easy to shape, and the neat arrangement of the ends is conducive to heat dissipation and enhanced mechanical strength.

Disadvantages: c. The number of coils is twice that of single-layer windings, so the embedding is labor-intensive. b. In the same slot, due to the embedding of different-phase coil sides, short-circuit faults are more likely to occur than single-layer windings. c. Insulation is required between layers, and the slot fullness rate is low.

Application range: Large-capacity motors can basically use double-layer windings, and large and medium-sized motors generally use double-layer windings.

Classification:

a. Double-layer stacked windings Two coil elements are embedded in each slot of the stacked windings, and the two elements of each coil are arranged in the upper and lower layers of the two slots of the winding pitch. That is, when winding, any two adjacent coils are "tightly stacked" on the other. It is widely used in the stator and rotor windings of three-phase asynchronous motors.

The stacked winding can flexibly select the coil pitch to improve the waveform of the electromotive force and magnetomotive force. It is easy to manufacture, but it is difficult to embed the wire as a whole, especially the last few coils of the motor. Short-distance coils can save copper at the end, but due to the large number of connections between coil groups, the copper consumption is large when the number of poles is large. Excellent electrical performance.

b. Double-layer wave windings The coils of wave windings are generally single-turn, that is, any two coils move forward like waves along the direction of the line system. The main feature is that one coil is connected in series with the coil under the adjacent same-sex magnetic pole. In order to reduce the connecting wires between coil groups, it is mostly used in the electronic windings of hydro-turbine generators and the winding rotor windings of induction motors. However, since the wave winding coil is mostly made of flat copper wire, its manufacturing process is relatively complicated.

3. Single-double layer hybrid winding

Definition: It is essentially a deformation of the short-distance double-layer winding. The upper and lower coils of the same slots in the short distance are combined into a single-layer side by removing the interlayer insulation strip, while the slots of the upper and lower layers with different phases are still kept as double-layer sides, and their ends are reconnected according to the needs of the current flow direction in the slot, which becomes a single-double layer hybrid winding.

Advantages: Single-double layer windings can show their different characteristics and features when used in different occasions, which can improve the efficiency of the motor, reduce the temperature, improve the starting characteristics, and save copper for windings.

Note: a. Single-double layer hybrid windings are most suitable for equivalent changes of double-layer stacking. It is not recommended to improve from single-layer windings, which will reduce the fundamental wave winding coefficient, and the coils must be rewound and embedded, which wastes time. b. It is not recommended to change the winding with ≤2 slots per pole per phase to a single-double layer hybrid winding, because the winding span before and after the transformation cannot be reduced, and it is impossible to save materials and energy. c. It is not recommended to change the winding with fraction per phase per slot (when the denominator is ≥ 4) to a single-layer mixed winding, because there is an asymmetric distribution between phases and between the pole-phase groups of the same phase. If it is changed to a single-layer winding, the winding and the wire embedding are very inconvenient and the average span is not shorter than the double-layer winding.

IV. Comparison

1. Some special needs, such as pole changing, can be achieved by double-layer windings but not by single-layer windings. 2. Double-layer windings are more cost-effective than single-layer windings. 3. At critical low voltage, double-layer windings can be started, but single-layer windings cannot. 4. The upper and lower windings of double-layer windings are sometimes not necessarily one phase, so the interphase insulation of single-layer windings is better than that of double-layer windings.

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