Induction motor

Abstract

To provide an induction motor that can eliminate the effects of unnecessary components contained in the rotating magnetic field caused by a stator current.SOLUTION: In an induction motor 1, a stator winding 22 is a fractional slot concentrated winding, a rotor winding 32 is a full pitch winding, and the number of poles of the rotor 3 is P, the number of slots of the stator 2 is M, the greatest common divisor of P / 2 and M is G, the order of the harmonic component that generates the force that drives the rotor 3 is νm, and the order of its harmonic is νn. The number of poles P is set such that major harmonic components other than the harmonic component of order νm calculated by the equation (1) are not included in the harmonic component of order νn calculated by the equation (2). νm=P / (2G) (1). νn=(2K+1)νm (2). Here, P is an even number, and K is a natural number greater than or equal to 1, and does not include the case where νn is a multiple of the number of phases of the input power.SELECTED DRAWING: Figure 1A

Description

[Technical field]

[0001] The present invention relates to an induction motor. [Background technology]

[0002] Induction motors are excellent in terms of self-starting, reliability, and economy, and are therefore widely used as industrial drive devices for pumps, fans, compressors, etc. In terms of structure, they generally have a distributed winding stator winding and a cage winding rotor winding.

[0003] However, when the stator winding is distributed winding, the parts that protrude outward from both ends of the stator core, known as coil ends, become longer, which results in problems such as large copper loss in the winding coil at the coil ends, increased copper usage, and an increase in the longitudinal dimension of the entire motor.

[0004] On the other hand, if the stator winding is a concentrated winding, these problems caused by the long coil ends can be avoided. On the other hand, in an induction motor with a concentrated winding stator winding, the magnetic flux density distribution in the gap between the stator and rotor contains several space harmonics with different wavelengths.

[0005] In an induction motor, a rotating magnetic field is generated by the stator current, which induces a rotor current, and the rotating magnetic field and rotor current generate a torque that rotates the rotor. In an induction motor with concentrated stator winding, the magnetic flux density distribution in the gap contains several space harmonics, and the rotating magnetic field of each space harmonic induces a rotor current, generating a torque corresponding to each.

[0006] In an induction motor with concentrated stator windings, the largest torque from the rotating magnetic field due to the main space harmonics contributes to driving the rotor. On the other hand, the rotating magnetic field due to other space harmonics rotates at a different speed from the above, and therefore has a negative effect on driving the rotor. This problem cannot be avoided if the rotor is a conventional squirrel-cage winding.

[0007] In contrast, Patent Document 1 describes a rotating electric machine in which the stator is provided with a concentrated winding coil and the rotor is provided with at least two sets of squirrel-cage short-circuit winding conductors that are electrically separated from each other. The squirrel-cage short-circuit winding conductors described in Patent Document 1 have rotor windings (conductors) in the same form as distributed winding wave windings. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Special Publication No. 2007-507192 Summary of the Invention [Problem to be solved by the invention]

[0009] The stator described in Patent Document 1 is a three-slot, two-pole fractional slot concentrated winding. In this case, the fundamental, second, fourth, and fifth harmonics are the main components of the space harmonics of the magnetic flux density distribution in the gap. The component required for driving in this case is the fundamental. Of the other components, the rotor winding suppresses the second and fourth harmonics, but does not have a complete suppression effect on the fifth harmonic. This causes problems such as increased torque pulsation and inability to self-start.

[0010] The present invention has been made to solve such problems, and has an object to provide an induction motor that can eliminate the effects of unnecessary components contained in the rotating magnetic field caused by the stator current. [Means for solving the problem]

[0011] In order to solve the above-mentioned problems, the present invention provides a rotor having a rotor winding and a stator winding that faces the stator, the stator winding being a fractional slot concentrated winding in which a winding is wound in series on each tooth of the stator, the rotor winding being a full pitch winding, and the number of poles of the rotor is P, the number of slots of the stator is M, the greatest common divisor of P / 2 and M is G, and the order of the harmonic component that generates the force that drives the rotor is ν m, and the order of the harmonic component is ν n Then, the number of poles P is the order ν m The main harmonic components other than the harmonic components of are of order ν n This is an induction motor in which the value is set so as not to be included in the harmonic components of ν m =P / (2G) (1) ν n =(2K+1)ν m (2) Here, P is an even number. K is a natural number equal to or greater than 1, and ν n This does not include values ​​where is a multiple of the number of phases of the input power. Effect of the Invention

[0012] In the present invention, it is possible to suppress the generation of torque resulting from unnecessary components contained in the rotating magnetic field caused by the stator current. [Brief description of the drawings]

[0013] [Figure 1A] 1 is a cross-sectional view showing an example of an induction motor according to an embodiment of the present invention. [Figure 1B] 2 is a connection diagram of a rotor showing an example of an induction motor according to the present embodiment. FIG. [Figure 2A] 11 is a perspective view showing another example of a rotor of the induction motor according to the present embodiment. FIG. [Figure 2B] FIG. 4 is a circuit diagram of a rotor showing another example of the induction motor according to the present embodiment. [Figure 3A] FIG. 13 is a perspective view showing a rotor of a comparative example. [Figure 3B] FIG. 4 is a circuit diagram of a rotor of a comparative example. [Figure 4] FIG. 4 is a cross-sectional view showing an induction motor of a comparative example. [Diagram 5] 1 is a graph showing torque-speed characteristics of induction motors of an embodiment and a comparative example when supplied with a voltage of 60 Hz and 40 V. [Figure 6A] FIG. 4 is an explanatory diagram showing the dimensional relationship between a stator and a rotor. [Figure 6B]FIG. 4 is an explanatory diagram showing the dimensional relationship between a stator and a rotor. [Figure 6C] FIG. 4 is an explanatory diagram showing the dimensional relationship between a stator and a rotor. [Figure 6D] FIG. 4 is an explanatory diagram showing the dimensional relationship between a stator and a rotor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an induction motor according to the present invention will now be described with reference to the drawings.

[0015] Fig. 1A is a cross-sectional view showing an example of an induction motor according to the present embodiment, Fig. 1B is a rotor connection diagram showing an example of the induction motor according to the present embodiment, Fig. 2A is a perspective view showing another example of the rotor of the induction motor according to the present embodiment, and Fig. 2B is a rotor circuit diagram showing another example of the induction motor according to the present embodiment.

[0016] The induction motor 1 of this embodiment includes a stator 2 and a rotor 3 facing the stator 2. The stator 2 includes a plurality of slots 20 formed in the circumferential direction, teeth 21 that are provided at predetermined intervals in the circumferential direction and between which the slots 20 are formed, and a stator winding 22 wound around the teeth 21.

[0017] The stator 2 is configured with fractional slot concentrated winding in which a stator winding 22 made of a wire material such as copper is wound in series around each tooth 21.

[0018] The rotor 3 includes a plurality of slots 30 formed in the circumferential direction, a core 31 in which the slots 30 are formed, and rotor windings 32 inserted in the slots 30 .

[0019] The rotor 3 is configured with full-pitch winding, in which the pitch of the coils configured with the rotor winding 32 is equal to the magnetic pole pitch. When the rotor winding 32 is made of wire such as copper, the rotor 3 has three-phase rotor windings 32 indicated by U, V, and W in FIG. 1A, and the rotor windings 32 are passed through the slots 30 in a predetermined path that forms a wave winding, for example, as shown in FIG. 1B. In the rotor 3, the three-phase rotor windings 32 are connected to each other in a star connection by short-circuit wires 32a. The rotor winding 32 may be lap winding. Both are full-pitch windings, and when configured with windings, they are lap windings, and when configured with die casting, they are wave windings.

[0020] In addition, when the rotor 3 has the rotor winding 32 formed into a predetermined shape by a molding method such as die casting a conductor such as aluminum or copper, the rotor winding 32 passed through the slots 30 is connected at the short-circuit parts 32b so that it becomes a wave winding, for example, as shown in FIG. 2A.

[0021] Next, in an induction motor 1 in which the stator 2 has fractional slot concentrated winding and the rotor 3 has full pitch winding, we will explain the relationship between the number of slots in the stator 2, the number of poles in the rotor 3, and the components that generate the force (torque) that drives the rotor 3 and other major components in the space harmonics contained in the magnetic flux density distribution in the gap between the stator 2 and rotor 3.

[0022] When the order of the spatial harmonic included in the magnetic flux density distribution in the gap between the stator 2 and the rotor 3 is ν, the order of the harmonic component that generates the force that drives the rotor 3 is ν. m , and the order of the harmonic component is ν n Let P be the number of poles of the rotor 3, M be the number of slots of the stator 2, and G be the greatest common divisor of P / 2 and M. The number of slots M and the number of poles P are the order ν m The main harmonic components other than the harmonic components of are of order ν n The value is not included in the harmonic components of

[0023] ν m =P / (2G) (1) ν n =(2K+1)ν m (2)

[0024] Here, P is an even number. K is a natural number equal to or greater than 1, and ν n This does not include values ​​where is a multiple of the number of phases of the input power.

[0025] When the number of phases of the input power is three, the number of slots M of the stator 2 and the number of poles P of the rotor 3 that satisfy the above conditions in equations (1) and (2) will be considered.

[0026] When the number of slots M of the stator 2 is 12 and the number of poles P of the rotor 3 is 10, G=1, and from equation (1), the order ν m = 5. Therefore, in this case, the fifth harmonic is the main spatial harmonic component that generates the force that drives the rotor 3. The other main harmonic components are the fundamental wave (ν = 1) and the seventh harmonic (ν = 7), but neither of them satisfies equation (2) (ν ≠ ν n ) Note that since the number of phases of the input power is 3, ν n , i.e., ν=15 is not included. ν=25 is the ν n However, since the 25th harmonic is not a major component, the effect of this component can be ignored.

[0027] As a result, it can be seen that, as an example that satisfies the above conditions, when the stator 2 has 12 slots and the rotor 3 has 10 poles, it is sufficient to prevent the rotor current from being induced by the fundamental wave and seventh harmonic of the magnetic flux density distribution in the gap. Next, the reason why it is possible to suppress the induction of the rotor current by a space harmonic of a specified order contained in the magnetic flux density distribution in the gap will be explained.

[0028] In an induction motor 1 in which the stator 2 is a fractional slot concentrated winding, by making the rotor 3 a full pitch winding, it is possible to eliminate components other than the harmonic components that generate the force that drives the rotor 3.

[0029] The filtering effect of providing full-pitch winding to the rotor 3 can be theoretically estimated from the rotating magnetic field. Therefore, the presence or absence of the filtering effect of space harmonics in the induction motors of the example and comparative example will be theoretically estimated from the rotating magnetic field.

[0030] As shown in Fig. 2A, the induction motor 1 of the embodiment has a rotor 3 with 10 slots, a rotor winding 32 with wave winding, and a stator (not shown) with fractional slot concentrated winding. Fig. 3A is a perspective view showing a rotor of a comparative example, and Fig. 3B is a circuit diagram of the rotor of the comparative example. In the comparative example, the number of slots 30B of the rotor 3B is 10, and the conductors 32B (rotor windings) inserted in the slots 30B are short-circuited by end rings 33B provided at both ends of the core 31B to form a squirrel-cage shape. Note that, in the case of a 10-pole rotor, the rotor requires 10 or more slots, so in the following explanation, the number of slots of the rotor is 10.

[0031] The spatial and temporal magnetic flux density distribution Bs(t, θs) in the air gap between the stator and rotor in the stator angular coordinate at time t and position θs is approximately expressed by the following equation (3).

[0032]

number

[0033] In equation (3), Bsν (ν=1,5,7) indicates the amplitude of the space harmonic of order ν, and ω indicates the angular frequency of the current (called the stator current) flowing through the stator winding. ν=1 indicates the fundamental wave, ν=5 indicates the 5th harmonic (5th harmonic), and ν=7 indicates the 7th harmonic (7th harmonic).

[0034] Furthermore, the rotor current induced by space harmonics can be estimated from the electromotive force induced in the conductor of each rotor slot. When the rotor slots are numbered 1, 2, etc., the electromotive force Er induced in the rotor winding in the slot with position number n is given by the following equation (4).

[0035]

number

[0036] In equation (4), θm denotes the angular position of the rotor, and Erν (ν=1, 5, 7) denotes the electromotive force at the spatial harmonic of order ν.

[0037] Furthermore, the electromotive force Erν (ν=1, 5, 7) in the space harmonic component induced in the rotor winding in the slot with position number n at time t and angular position θm is shown in the following equations (5a), (5b), and (5c).

[0038]

number

[0039] If the rotor has a squirrel-cage shape as shown in FIG. 3A, the current Ir induced in the conductor (rotor winding) in the slot with position number n as shown in FIG. 3B is given by the following equation (6).

[0040]

number

[0041] If the rotor is a squirrel cage as shown in Figure 3A, ignoring the electrical resistance of the end rings, no voltage is generated between both end rings that short-circuit the conductors in the slots, so the rotor current is induced by all the major space harmonics. This shows that the rotor current Ir is induced at the fundamental, fifth and seventh harmonics, and the fundamental and each harmonic contribute to torque generation. Therefore, if an attempt is made to drive the rotor with the torque induced by the rotor current induced by the fifth harmonic, starting will be hindered by the torque induced by the rotor current induced by the fundamental and seventh harmonics, and torque pulsation may increase.

[0042] In contrast, if the rotor has a wave winding shape as shown in FIG. 2A, the current Ir induced in the conductor (rotor winding) in the slot is expressed by the following equation (7).

[0043]

number

[0044] It can be seen that when the rotor is wave-wound as shown in Fig. 2A, the rotor current is induced only by the fifth harmonic, and the fundamental and seventh harmonics do not contribute to torque generation. Therefore, it can be seen that when the rotor is wave-wound as shown in Fig. 2A, it has a filtering effect on the desired space harmonics generated in the rotating magnetic field.

[0045] The torque-speed characteristics of an induction motor can be predicted by finite element method (FEM) analysis. Therefore, the torque-speed characteristics of the induction motors of the embodiment and the comparative example are numerically predicted by finite element method analysis. As shown in FIG. 1A, the induction motor 1 of the embodiment has 12 slots 20 in the stator 2 and 10 poles in the rotor 3, the stator winding 22 is fractional slot concentrated winding, and the rotor winding 32 is wave winding as shown in FIG. 1B. FIG. 4 is a cross-sectional view showing an induction motor of the comparative example. The induction motor 1C of the comparative example has 12 slots 20C in the stator 2C and 10 poles in the rotor 3C. The stator 2C has a stator winding 22C that is fractional slot concentrated winding. The rotor 3C is a squirrel-cage type in which both ends of a conductor 32C inserted in a slot 30C formed in a core 31C are short-circuited at a short-circuit portion 32D. The rotor 3 of the induction motor 1 of the embodiment and the rotor 3C of the induction motor 1C of the comparative example both have 30 slots.

[0046] FIG. 5 is a graph showing the torque-speed characteristics of the induction motors of the embodiment and the comparative example when supplied with a voltage of 60 Hz and 40 V.

[0047] The comparative induction motor, which has a cage rotor, has a rotor speed of 600 min -1However, the torque in the low speed range is lower than the maximum torque generated in the high speed range, which is considered to be mainly due to the influence of the fundamental wave and the seventh harmonic, and is considered to reflect that current is induced from all the major space harmonics as a theoretical estimation of a squirrel-cage rotor, and indicates that the induction motor of the comparative example, which has a squirrel-cage rotor, cannot achieve self-starting.

[0048] In contrast, the induction motor of the embodiment, which has a wave-wound rotor, has a rotor rotation speed of more than 0 to 540 min -1 It can be seen that a nearly constant torque of 10 Nm can be generated in a speed range of about 100 rpm. This shows that the induction motor of the embodiment, which has a wave-wound rotor, can achieve self-starting. The same effect can be achieved even if the rotor is lap-wound.

[0049] In the case of a 3-slot, 2-pole, fractional slot concentrated winding as in the embodiment described in Patent Document 1, the fundamental, second, fourth, and fifth harmonics are the main components of the space harmonics of the magnetic flux density distribution in the gap. Since the number of poles of the stator is P=2, the order ν m = 1, and the fundamental wave generates a force that drives the rotor. When v = 2 or v = 4, formula (2) is not satisfied, so the second and fourth harmonics can be suppressed. However, when v = 5, formula (2) is satisfied, so the fifth harmonic cannot be suppressed. For this reason, in a 3-slot, 2-pole induction motor as in Patent Document 1, even if the stator has fractional slot concentrated winding and the rotor has wave winding, it is thought that the motor will exhibit torque-speed characteristics equivalent to those of the comparative example shown in FIG. 5, and there is a possibility that problems such as increased torque pulsation and inability to self-start will occur.

[0050] In contrast, the induction motor of the embodiment does not show such characteristics. This means that in a wave-wound or lap-wound rotor in which the order ν of the space harmonics, the number of slots M, and the number of poles P satisfy the above conditions in equations (1) and (2), currents other than those required for driving are not induced among the main harmonic components, and this is considered to support the filtering effect of the space harmonics by the rotor.

[0051] Furthermore, if the three sets of wave winding conductors corresponding to each of the three phases are electrically isolated from one another as in the embodiment described in Patent Document 1, the phases will not be balanced, which may result in problems such as increased torque pulsation and inability to self-start.

[0052] 1B, the rotor 3 has three-phase rotor windings 32 connected to each other in star connection by short-circuit wires 32a. By connecting three sets or an odd number of sets of rotor windings 32 in this way in a Y- or star-connection, it is possible to balance the phases, suppress torque pulsation, and ensure self-starting.

[0053] In addition, by using concentrated winding for the stator winding 22, the coil ends become shorter, and therefore the copper loss of the winding coil at the coil ends becomes smaller compared to when the stator winding 22 is distributed winding, and when the stator winding 22 is made of copper wire, the amount of copper used can be reduced, and the longitudinal dimension of the entire motor can be shortened. On the other hand, the rotor winding 32 has a smaller number of turns and a smaller slot step area than the stator winding 22, and therefore even if it is configured as wave winding or lap winding, the coil end portion is also small, so the increase in the longitudinal dimension of the entire motor is suppressed, and if the rotor winding 32 is configured by die casting of the wave winding, it can be manufactured using the same manufacturing process as the conventional squirrel-cage winding.

[0054] 6A, 6B, 6C, and 6D are explanatory diagrams showing the dimensional relationship between the stator and rotor, and next, the effect of the opening width of the stator slot will be explained. When the side surface of the stator tooth is straight, as in the embodiment described in Patent Document 1, the opening width of the slot becomes wide. When the opening width of the slot becomes wide, the required current increases and the power efficiency decreases.

[0055] Therefore, when the stator 2 is configured with concentrated winding, it is possible to provide a flange portion 21a in the form of a protruding side of the tooth portion 21 and narrow the opening width C of the slot 20 of the stator 2 to reduce the required current.

[0056] 6D, if the opening width C of the slot 20 of the stator 2 is made narrower than the tooth width E of the rotor 3, for example, the tooth width E of the rotor 3 straddles the opening width C of the slot 20 of the stator 2, causing leakage flux to flow from the stator 2 through the gap G to the rotor 3 and then back to the stator 2, as shown by the two-dot chain line. The leakage flux does not interlink with the rotor winding, causing problems such as an increase in induced electromotive force and a decrease in power factor.

[0057] When the opening width of the slot 20 of the stator 2 is C and the pitch of the slot 30 of the rotor 3 is D, the dimensional relationship between them that can suppress the influence of leakage magnetic flux is expressed by the following formula (8).

[0058] C≧D (8)

[0059] When the dimensional relationship between the opening width C of the slot 20 of the stator 2 and the pitch D of the slot 30 of the rotor 3 is defined as in formula (8), the opening width F of the slot 30 of the rotor 3 is always interposed between adjacent teeth 21 of the stator 2, without the tooth width E of the rotor 3 straddling the opening width C of the slot 20 of the stator 2, regardless of the angular position of the rotor 3 relative to the stator 2. This increases the resistance of the magnetic path, making it possible to suppress leakage magnetic flux returning from the stator 2 to the stator 2 via the rotor 3.

[0060] Fig. 6A shows the case where C=D, and Fig. 6B shows the case where C=1.5D. In either case, the magnetic path resistance passing through the teeth 21 of the stator 2 via the rotor 3 is the same, being 1x. In contrast, in the case of C=2D shown in Fig. 6C, this magnetic path resistance doubles. Although not shown, in the case of C=2.5D, the magnetic path resistance is twice as high as in the case of C=D, just like in the case of C=2D.

[0061] Therefore, in the present invention, when the pitch of the slots 20 of the stator 2 is A, the opening width of the slots 20 of the stator 2 is C, and the pitch of the slots 30 of the rotor 3 is D, N is a natural number, and the dimensional relationship between these is defined by the following equation (9).

[0062] A>C=N×D (9)

[0063] From equations (8) and (9), it is possible to suppress the leakage magnetic flux passing through the rotor 3 by making the pitch A of the slots 20 of the stator 2 more than N times the pitch D of the slots 30 of the rotor 3. For example, in both cases of C=D and C=1.5D, the magnetic path resistance passing between the teeth 21 of the stator 2 is the same. Therefore, it is possible to find the minimum opening width C of the slots 20 of the stator 2 when the suppression effect of the leakage magnetic flux passing through the rotor 3 is the same.

[0064] As a specific example, if the stator 2 has 12 slots and the stator winding 22 is a fractional slot concentrated winding, and the rotor 3 has 10 poles and the rotor winding 32 is three-phase, the pitch A of the slots 20 of the stator 2 is as follows: A=360° / 12(number of slots)=30°, The pitch D of the slots 30 of the rotor 3 is D=360° / (10 poles x 3 phases; number of slots: 30)=12° It is.

[0065] When N=1, the opening width C of the slot 20 of the stator 2 is C = 1 × 12° = 12°, The tooth width B of the stator 2 is B=AC=30°-12°=18° It is.

[0066] For the rotor 3, the pitch D of the slots 30 of the rotor 3 is: D = (opening width F of slot 30 of rotor 3 + tooth width E of rotor 3) If F=2°, then E=10°.

[0067] When N=2, the opening width C of the slot 20 of the stator 2 is C = 2 × 12° = 24°, The tooth width B of the stator 2 is B=AC=30°-24°=6° For rotor 3, it is the same as for N=1.

[0068] When N=3, the opening width C of the slot 20 of the stator 2 is C=3×12°=36°, which exceeds the pitch A of the slot 20 of the stator 2=30°, so N=3 or more is not possible.

[0069] Comparing the cases of N=1 and N=2, the opening width C of the slots 20 of the stator 2 is smaller when N=1, which is advantageous in terms of reducing the required current. However, a smaller opening width C means that there is a possibility that leakage flux will increase in the path that passes directly between the teeth 21 of the stator 2 without passing through the rotor 3. Also, the suppression effect of leakage flux passing through the rotor 3 is half that of N=2.

[0070] Therefore, the opening width C of the slot 20 of the stator 2 can be selected taking into consideration the required current, the leakage magnetic flux passing through the rotor 3, and the leakage magnetic flux passing directly between the teeth 21 of the stator 2 without passing through the rotor 3. [Explanation of symbols]

[0071] 1 induction motor, 2 stator, 20 slot, 21 teeth, 22 stator winding, 3 rotor, 30 slot, 31 core, 32 rotor winding, 32a short-circuit wire, 32b short-circuit portion

Claims

1. a stator having a stator winding; a rotor having a rotor winding and facing the stator; The stator winding is a fractional slot concentrated winding in which a winding is wound on each tooth of the stator in series, and the rotor winding is a full pitch winding, The number of poles of the rotor is P, the number of slots of the stator is M, the greatest common divisor of P / 2 and M is G, and the order of the harmonic component that generates the force that drives the rotor is ν ｍ , and the order of the harmonic is ν ｎ When The number of poles P is the order v obtained by equation (1) ｍ The main harmonic components other than the harmonic components of the order ν ｎ The value is set to be not included in the harmonic components of induction motor. n ｍ =P / (2G)・・・(1) n ｎ =(2K+1)n ｍ ・・・(2) Here, P is an even number. K is a natural number equal to or greater than 1, and ν ｎ This does not include values ​​where is a multiple of the number of phases of the input power.

2. order ν ｍ is greater than or equal to 2 2. The induction motor according to claim 1.

3. M=12, P=10 2. The induction motor according to claim 1.

4. The rotor windings are Y-connected or star-connected with three or odd number of windings.

2. The induction motor according to claim 1.

5. When the pitch of the stator slots is A, the opening width between the stator slots is C, and the pitch of the rotor slots is D, A>C=N×D (N is a natural number) The induction motor according to any one of claims 1 to 4.

6. A stator having a stator winding; a rotor having a rotor winding and facing the stator; The stator winding is a fractional slot concentrated winding in which a winding is wound on each tooth of the stator in series, and the rotor winding is a full pitch winding, The rotor windings are Y-connected or star-connected with three or odd number of windings. induction motor.

Images