This Paper Analyzes the Performance and Characteristics of End Connection Mode of Three-phase Single

Single layer is a winding with only one effective side of the coil embedded in each stator slot, so its total number of coils is only half of the total number of slots of the motor. The advantages of single-layer winding are convenient wire embedding and high slot utilization. The disadvantages are that the selection of pitch is limited and the electromagnetic performance of motor is not ideal. It is mostly used in small and medium-sized motors.

The stator winding is divided into two types: explicit pole type and implicit pole type.

(1) The two pole phase groups with the same phase span in two adjacent pole planes are connected by "head joint" and "tail to tail", which is called pole display winding. In the pole explicit winding, each pole phase group forms a magnetic pole, and the number of pole phase groups of each phase winding is equal to the number of magnetic poles. In other words, there are several pole phase groups in the pole display winding, and the motor is a motor with several poles. Figure 5-8 shows the schematic diagram of one phase of 4-pole explicit winding.

In the explicit pole winding, in order to make the polarity N and s of the magnetic poles separated from each other, the current direction in the two adjacent pole phase groups is opposite, but the current direction in the effective side of the two adjacent coils is the same.

(2) Hidden pole (common pole) winding is called hidden pole winding, as shown in Figure 5-9. The two pole phase groups in the same phase in two non adjacent pole surfaces are connected by "head to tail" and "tail joint". In the hidden pole winding, each pole phase group forms two magnetic poles, the number of pole phase groups of the winding is half of the number of magnetic poles, and the other half of the magnetic poles are formed by the magnetic flux generated by the pole phase group. That is to say, in the motor with hidden pole winding, the number of poles is twice the number of pole phase groups of each phase winding.

Figure 5-8 pole display winding

Figure 5-9 hidden pole winding

In the hidden pole winding, the polarity of the magnetic pole formed by each pole phase group is the same, and the current direction of all pole phase groups is the same.

Hidden pole winding is mostly used in old motors and has been eliminated now. Modern motors are only used in the windings of two speed motors, and there is only one set of stator windings of two speed motors. The wire embedding method is the same as that of single speed motors. The difference is that the purpose of variable speed is achieved by changing the number of poles (i.e. changing the mode of displaying and hiding poles).

Form of three-phase single-layer winding

According to different winding shapes, single-layer winding is divided into chain type, concentric type and cross type.

(1) Chain winding chain winding is composed of single-layer coil elements with the same shape and pitch. It is named because each coil at the winding end looks like a sleeved chain link. Figure 5-10 shows the pitch of three-phase 24 slot 4-pole single-layer chain winding.

Single layer chain winding is convenient for winding due to equal pitch. When making chain arrangement, there are many cross connections at the end, and it is difficult to shape the end.

Figure 5-10 pitch of three-phase 24 slot 4-pole single layer chain winding

â–³ note: the coil pitch of single-layer chain winding must be odd, otherwise the winding will not be arranged.

(2) Cross winding cross winding is formed by the cross arrangement of two winding elements with different pitch, one large and one small. Its characteristic is that although the winding of elements is not as convenient as chain winding, short pitch winding can be used, which is conducive to improving the performance of motor. Figure 5-11 shows the expanded view of three-phase 36 slot 4-pole single-layer cross winding (phase a).

Figure 5-11 three phase 36 slot 4-pole single layer cross chain winding (phase a)

(3) Concentric winding concentric winding is composed of two coils with different pitch in the same polar phase group. It is named because all coils in the polar phase group surround the same center. Concentric winding is characterized by different pitch sizes of elements in the same polar phase group. Several molds of different sizes are required during winding, but several elements are placed concentrically, and the end connections do not cross each other, which is easy to be arranged neatly. Figure 5-12 shows the expanded view of 24 slot 2-pole single-layer concentric winding.

Fig. 5-12 expanded view of 24 slot 2-pole single layer concentric winding a) A-phase winding b) three-phase winding

Performance and characteristics of end connection mode of three-phase single-layer winding

1. Equal width type (stacked type)

The coils are equidistant, the pitch of all coils is the same, and the wire mold is easy to adjust; The coil pitch is shorter than the pole pitch (whole pitch), which saves wire; The number of coils of single-layer winding is small, and embedding wire saves time, but the electrical performance is poor.

2. Concentric

The winding is single-layer wiring with high slot filling rate; The average value of coil pitch is equidistant, the length of winding end is large, the wire is consumed, the magnetic flux leakage is large, and the electrical performance is poor; Layered wire embedding can be used to form "double plane" or "three plane" windings, which makes wire embedding convenient and is mostly suitable for two pole motors.

3. Cross type

The winding is full pitch, but the average pitch of the coil is short, so the wire is saved; The number and pitch of each group of coils are different, which increases the difficulty of wire embedding process; High tank filling rate and poor electrical performance. In addition, the end connection mode can also be concentric cross type, that is, two coils with equal width can be changed into concentric type.

4. End connection mode of three-phase single-layer 4-pole 36 slot winding

According to the three-phase 4-pole 36 slots, the number of slots per pole of the winding is q = 3. There may be three end connection modes, which are depicted in figures (a), (b) and (c), and only one phase is connected.

(a) Equal width type (chain type)

(b) Concentric

(c) Cross type

In practice, the choice of end connection mode is not considered by the repairman, but only by the designer. For the repairman, under normal circumstances, the original design data is an important basis for rewinding the motor and cannot be changed.

5. End connection mode of three-phase single-layer 4-pole 24 slot winding

According to the two basic parameters of three-phase 4-pole 24 slots, it can be calculated that the number of slots per pole = 2. According to its regular arrangement, there are three end connection modes, as shown in the figure below.

(a) Equal width (stacked)

(b) Concentric

(c) Single chain

In short, the above single-layer winding types have the advantages of high slot utilization, less phase to phase short circuit, less number of coils, less wire embedding time and so on. They are widely used in small motors. In common Y series motors, single-layer laminated winding is used for 4, 6 and 8-pole motors with q = 2; Single layer cross winding is used for 2 and 4-pole motors with q = 3; Concentric windings are used for 2-pole motors with q = 4. These winding types are often seen in daily repair work. In addition, due to the limited structure of single-layer winding, its winding end is thick and difficult to shape, so it is impossible to use appropriate short distance to improve the electromagnetic performance of winding, which is the reason for the poor performance of single-layer winding motor.