A standard phase belt integer-slot short-pitch wave winding 4-branch connection method

Abstract

The application discloses a standard phase belt integer-slot short-pitch wave winding 4-branch connection method, which has the following electrical characteristics: the number of motor phases m is 3, the number of motor pole pairs p is an odd number, the number of slots is Z, the number of slots per pole per phase q is an integer, the short-pitch amount of the winding is s slots, the short-pitch ratio is beta=1-s / (3q), the first pitch y1 of the winding is 3q+s, the synthetic pitch y is 6q, and the second pitch is under the above electrical characteristics. The connection method comprises the following steps: 1) dividing positive and negative phase belts; 2) exchanging the lower layer coil edges under the pth pole pair among phases; and 3) forming new coils and constructing winding branches. The method of exchanging coil edges among phases not only realizes the short-pitch of the winding to weaken the 5th and 7th harmonics, but also balances the 4 parallel branches and eliminates the circulating current of the parallel branches; the branches among three phases are completely symmetrical, and the theoretical limitation that the traditional standard positive and negative phase belt design method does not have symmetrical 4 branches for the integer-slot short-pitch winding when the number of pole pairs is an odd number is broken through.

Description

Technical Field

[0001] This invention relates to the field of three-phase AC motor winding technology, specifically to a wiring method for a symmetrical four-branch standard phase short-pitch wave winding with an integer number of pole pairs when the number of pole pairs in the motor is odd. Background Technology

[0002] Due to the large number of poles and slots in hydro-generators, the winding design commonly utilizes the standard phase band coil group cycle sequence, employing a positive and negative phase band design method, referred to as the standard phase band design method. The winding design generally follows the principle of using short-pitch windings to weaken the 5th and 7th harmonics. The short pitch is generally determined by the first pitch, which is usually both the structural pitch and the electrical pitch, with a short-pitch ratio β = 0.8–0.9 ≠ 1. According to the theory of the standard positive and negative phase band design method, when the number of pole pairs is odd, there is no symmetrical short-pitch parallel connection of four branches. Therefore, in practical applications, an asymmetrical parallel connection of four branches is sometimes used. While the asymmetrical four-branch design solves the short-pitch design problem, it always suffers from the disadvantage of asymmetrical branch potentials leading to fundamental and harmonic circulating currents, and even short-circuiting of higher harmonic potentials. Furthermore, the irregular adjustment of coil pitch makes the end wiring very complex. Summary of the Invention

[0003] To address the aforementioned shortcomings, this invention provides a standard phase band integer slot short-pitch winding 4-branch connection method. By exchanging the phase coil sides, not only is the short pitch of the winding achieved to weaken the 5th and 7th harmonics, but the parallel 4 branches are also symmetrically balanced, with no circulating current in the parallel branches; the three phase branches are completely symmetrical, breaking through the theoretical limitation of the traditional standard positive and negative phase band design method that the integer slot short-pitch winding does not have symmetrical 4 branches when the number of pole pairs is odd.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A standard phase-band integer-slot short-pitch wave winding with four branches has the following electrical characteristics:

[0006] The motor has 3 phases (m=3), an odd number of pole pairs (p), and Z slots. The number of slots per pole per phase (q=Z / (2pm)) is an integer. The short-pitch length of the winding is s slots, with a short-pitch ratio β=1-s / (3q). The first pitch of the winding is y1=3q±s, the combined pitch is y=6q, and the second pitch...

[0007] Under the above electrical characteristics, the wiring method includes the following steps:

[0008] Step S1: Divide the positive and negative phase bands;

[0009] Step S2: Interchange the lower coil sides under the p-th pole pair;

[0010] Step S3: Form a new coil and construct the winding branch;

[0011] This invention provides a standard phase-band integer slot short-pitch wave winding 4-branch connection method. The electrical characteristics are: motor phase number m = 3, motor pole pair number p is odd, slot number Z, number of slots per pole per phase q = Z / (2pm) is an integer, short-pitch amount of the winding is s slots, with a short-pitch ratio β = 1 - s / (3q), the first pitch of the winding y1 = 3q ± s, the combined pitch y = 6q, and the second pitch... The coils under the first to (p-1) pole pairs of each phase's standard positive and negative phase bands are divided into two groups, each occupying q slots, and connected according to conventional pitches y1 and y2. The remaining coils under the p-th pole pair undergo phase-to-phase exchange of the lower coil sides to distribute the upper and lower coil sides within a 60° phase band, and are then divided into two new coil groups, each occupying q slots. These new coil groups are then connected in series with the two equally divided coil groups under the first to (p-1) pole pairs to form two branches. Each phase's positive and negative phase bands form a total of four branches. Each branch corresponds to the same slot number, and the resulting branches are identical in terms of electromotive force and magnetomotive force. The three phases are arranged into four branches according to the same pattern. The winding constructed by this invention has a short-pitch structure with y1≠3q. The resulting electrical short pitch can weaken high-order harmonics. The branches of each phase are completely symmetrical in terms of electromotive force and magnetomotive force, and there is no circulating current between parallel branches. The branches between the three phases are also completely symmetrical, breaking through the theoretical limitation of the traditional standard positive and negative phase band design method that there are no symmetrical 4 branches in the integer slot short-pitch winding when the number of pole pairs is odd.

[0012] As a preferred option, the specific process of step S1 is as follows: the coils under the first to (p-1) pole pairs of the standard positive and negative phase bands of each phase are divided into two groups according to the principle of each occupying q slots, and connected according to the conventional pitches y1 and y2.

[0013] Preferably, the specific process of step S2 is as follows: the upper and lower coil sides of the remaining coil under the p-th pole pair are arranged with a short distance of s, and then the lower coil sides are exchanged in phase so that the upper and lower coil sides are distributed within the 60° phase band.

[0014] Preferably, the specific process of the phase-to-phase exchange of the lower coil side is as follows: the lower coil side originally belonging to the A+ phase band is exchanged to the lower coil side of the C- phase band, and the lower coil side originally belonging to the C- phase band is exchanged to the lower coil side of the B+ phase band. The exchange between the 6 phase bands is completed in a regular manner, so that the upper and lower coil sides under the p-th pole pair of each phase band fall within the 60° phase band.

[0015] As a preferred option, the specific process of step S3 is as follows: the upper and lower coil sides under the p-th pole pair are combined to form a new coil, the new coil is divided into two groups, each group occupies q slots, and is connected in series with the two equally divided coil groups under the 1 to (p-1) pole pairs to form 2 branches.

[0016] As a preferred embodiment, the positive and negative phase bands of each phase form a total of 4 branches, and each branch has a corresponding slot number of the same slot position. The branches formed are completely identical in terms of electromotive force and magnetomotive force.

[0017] As a preferred option, the three phases are arranged into four branches according to the same pattern.

[0018] Therefore, the advantages of this invention are: by exchanging the coil sides (conductors) between phases, the winding constructed by this invention has the short-pitch structure characteristic of y1≠3q. The resulting electrical short pitch can weaken high-order harmonics. The branches of each phase are completely symmetrical in terms of electromotive force and magnetomotive force. There is no circulating current between parallel branches. The branches between the three phases are also completely symmetrical. This breaks through the theoretical limitation of the traditional standard positive and negative phase band design method that there is no symmetrical 4 branches in the integer slot short-pitch winding when the number of pole pairs is odd. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a 4-branch wiring configuration with Z slots, 2p poles, and q slots per pole per phase in Example 1.

[0020] Figure 2 This is a schematic diagram of the 4-branch wiring with 252 slots, 14 poles, and 6 slots per pole per phase in Example 2. Detailed Implementation

[0021] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0022] Example 1:

[0023] The electrical features of this embodiment are: the number of pole pairs p of the motor is odd, the number of slots q per pole per phase is an integer, the double-layer wave winding is used, the winding achieves electrical short pitch with structural short pitch, and there are symmetrical 4 branches.

[0024] The technical theory of this embodiment is as follows: the number of pole pairs p of the motor is odd, the number of slots of the motor is Z, the number of phases m = 3, and the number of slots per pole per phase q = Z / (2pm) is an integer. The electrical short pitch of the short-pitch winding is taken as s (s is an integer less than q), so that the short pitch ratio β = 1 - s / (3q) is as close as possible to 0.833. The first pitch of the winding is y1 = 3q ± s, the combined pitch of the winding is y = 6q, and the second pitch of the winding... Based on the winding design of s, y1, and y2, the positive (or negative) phase band of each phase occupies q slots (electrical angle of 60°). The slot number represented by each positive (or negative) phase band is the upper layer edge of the coil. Including the lower layer edge of the coil, the total upper and lower layer edges of the coil in each phase band occupy q+s slots. The slot numbers under pole pairs 1 to (p-1) of each positive (or negative) phase band are evenly divided into two symmetrical branches. The upper and lower layer coil edges of the coil under the remaining p-th pole pair are exchanged phase-to-phase so that all the exchanged upper and lower layer coil edges fall within the 60° phase band range. Therefore, each slot within the 60° phase band range of that pole pair has one upper and lower layer coil edge. These are divided into two new coil groups, with each new coil group's upper and lower layer edges occupying q slots. Figure 1 As shown in (c), the electromotive force vectors generated by the two sets of coils are exactly the same. The total number of branches formed by connecting the two sets of coils in series to the two branches under the 1 to (p-1) pole pairs is a symmetrical branch. The positive and negative phase bands of each phase can form a total of 4 symmetrical branches. When q is even, the branch terminals are only led out at one end of the motor; when q is odd, each set of coils has 1 / 2 coils, and the terminals need to be led out at both ends of the motor. This embodiment theoretically derives the short-pitch coefficient algorithm for the symmetrical 4-branch connection method of the inter-phase coil sides: short-pitch ratio β=1-s / (3q), short-pitch coefficient k of the νth harmonic. sv The calculation is as follows:

[0025]

[0026] The specific process of this embodiment:

[0027] Step 1: Divide the positive and negative phase bands. For a motor with Z stator slots, 2p poles, and q slots per pole per phase, its positive and negative phase bands are as follows: Figure 1 As shown in (a). Since q is an integer, each phase's positive and negative phase bands each occupy 60° (electrical angle), taking up q slots. Each positive (or negative) phase band has p pole pitches longitudinally. Since p is an odd number, the coils with 1 to (p-1) pole pitches are evenly divided for connecting two branches in series, as shown in (a). Figure 1 (a) shows the C+ and C- phase bands grouped together. The coils enclosed by the solid ellipse and the coils enclosed by the dashed ellipse belong to two branches. Since the branches have the same slot number, the branches are symmetrical and balanced.

[0028] Step 2: Alternately swap the lower coil sides under the p-th pole pair. For the remaining coils under the p-th pole pair, list the upper and lower coil sides with short intervals of s, as follows: Figure 1 As shown in (b), the lower layer edges of the coil at the phase boundary are swapped phase-to-phase: Figure 1(b) At the position shown, the lower coil edge originally belonging to phase A+ is exchanged for the lower coil edge of phase C-; the lower coil edge originally belonging to phase C- is exchanged for the lower coil edge of phase B+, and so on, completing the exchange between the 6 phases in a regular manner. The result of the exchange is as follows: Figure 1 As shown in (c), the upper and lower coil sides under the p-th pole pair of each phase band fall within the 60° phase band;

[0029] Step 3: Form the new coil and construct the winding branches. The upper and lower coil sides below the p-th pole are as follows: Figure 1 (c) As shown by the slash, form a new coil. The new coil is divided into two groups, each occupying q slots. The new coils in the groups are connected in series with the coils in the first step 1 to (p-1) pole pairs to form two winding branches.

[0030] In this embodiment, the four branch windings are completely symmetrical with respect to the three phases, and the potentials of the four branches are also completely symmetrical and balanced for each phase, so there is no circulating current between the parallel branches.

[0031] Example 2:

[0032] Taking a 300MW-class generator motor with a voltage level of 15.75-18kV and a pole number of 2p=14, which is common in the pumped storage field, as an example, the specific implementation method for achieving symmetrical 4-branch number when using standard positive and negative phase band design short-pitch windings is as follows.

[0033] The motor has 3 phases (m), 14 poles (2p), and 7 pole pairs (p). If the number of slots is Z = 252, then the number of slots per pole per phase is... Take the electrical short distance s = 3, and the short distance ratio It can simultaneously weaken the 5th and 7th harmonics; take the first pitch of the winding y1=3q+s=3×6+3=21, the combined pitch y=6q=6×6=36, then the second pitch of the winding y2=y-y1=36-21=15.

[0034] The specific process of this embodiment:

[0035] Step 1: Draw a simplified block diagram of the positive and negative phase bands, as shown below. Figure 2 As shown in (a), the phase band block diagram represents the upper layer side slot number of the coil. The phase band slot numbers below pole pairs 1 to (p-1), i.e., 1 to 6, are divided into two groups, as follows: Figure 2 (a) shows the solid and dashed lines in the B+ and B- phase bands. The two groups of coils are connected with pitches y1 and y2 using the conventional method. Since the slot numbers of the groups all have corresponding slot numbers in the same slot position, the branches are completely symmetrical.

[0036] Step 2: List all slot numbers for the upper and lower layers of the coil under the 7th (p=7) pole pair according to s=3, such as Figure 2As shown in (b), the slot number relationship between the upper and lower coil sides is: lower side slot number = upper side slot number + y1. The slot number position is offset by s slots from the upper side slot number. Since y1 = 3q ± s is taken as +s, the position is offset backward (to the right) by s = 3. After phase-to-phase exchange of the lower side slot numbers at the phase band boundary, the phase band distribution below the 7th pole pair is as follows. Figure 2 As shown in (b);

[0037] Step 3: Combine the upper and lower coil sides of the 7th pole pair to form a new coil, and connect it in series with the coils that have already been grouped together for pole pairs 1 to 6. Each phase will form two branches, such as... Figure 2 (c) shows the branches composed of phases B+ and B-, each phase forming a total of 4 branches. The 4 branches of phase B ultimately form as follows: Figure 2 As shown in the wiring diagram (d), the upper right corner of the slot number in the wiring diagram indicates the difference between the new coil pitch and the standard pitch y1. Phases A and C also form branches according to the same pattern.

[0038] The winding features of this embodiment are: 1) three-phase symmetry; 2) the magnitude and phase of the electromotive force and magnetomotive force of each of the four branches are exactly the same, and there is no circulating current in the parallel branches; 3) the winding is a short-pitch winding, which can weaken higher harmonics. The winding coefficients of the 5th and 7th harmonics in this embodiment are only 6% and 5% of the fundamental winding coefficient, respectively.

[0039] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A standard phase-band integer-slot short-pitch wave winding 4-branch connection method, characterized in that, Its electrical characteristics are as follows: The number of phases of the motor is m=3, the number of pole pairs p is odd, the number of slots is Z, the number of slots per pole per phase is q=Z / (2pm) which is an integer, the short pitch of the winding is s slots, and it has a short pitch ratio β=1-s(3q). The first pitch of the winding is y1=3q±s, the combined pitch is y=6q, and the second pitch is y2=3q∓s. Under the aforementioned electrical characteristics, the wiring method includes the following steps: Step S1: Divide the positive and negative phase bands; The coils under the first to (p-1) pole pairs of each standard positive and negative phase band are divided into two groups according to the principle of each occupying q slots, and connected according to the conventional pitch y1 and y2. Step S2: Interchange the lower coil sides under the p-th pole pair; List the upper and lower coil sides of the remaining coil under the p-th pole pair with a short distance of s, and then perform phase-to-phase exchange of the lower coil sides so that the upper and lower coil sides are distributed within a 60° phase band. Step S3: Form a new coil and construct the winding branch; The upper and lower coil sides of the p-th pole pair form a new coil. The new coil is divided into two groups, each occupying q slots. The new coil and the lower grouped coils of the 1~(p-1) pole pairs are connected in series to form 2 branches.

2. The standard phase-band integer slot short-pitch wave winding 4-branch connection method according to claim 1, characterized in that, The specific process of the phase-to-phase exchange of the lower coil side is as follows: the lower coil side originally belonging to the A+ phase band is exchanged to the lower coil side of the C- phase band, and the lower coil side originally belonging to the C- phase band is exchanged to the lower coil side of the B+ phase band. The exchange between the 6 phase bands is completed in a regular manner.

3. The standard phase-band integer slot short-pitch wave winding 4-branch connection method according to claim 2, characterized in that, The upper and lower coil sides of each phase band below the p-th pole pair fall within the 60° phase band.

4. The standard phase band integer slot short-pitch wave winding 4-branch connection method according to claim 1, characterized in that, Each phase consists of four branches, with the positive and negative phase bands forming a total of four branches. Each branch has a corresponding slot number in the same slot position.

5. The standard phase-band integer slot short-pitch wave winding four-branch connection method according to claim 4, characterized in that, The resulting branches are identical in terms of electric and magnetic potentials.

6. The standard phase-band integer slot short-pitch wave winding 4-branch connection method according to claim 1, characterized in that, The three phases are arranged into four branches according to the same pattern.

7. The standard phase band integer slot short-pitch wave winding 4-branch connection method according to claim 1, characterized in that, When q is an even number, the branch terminals are only led out from one end of the motor; when q is an odd number, each group of coils has 1 / 2 coils, and the terminals need to be led out from both ends of the motor.

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