Rotor Slot Design Method Based on Motor Locked-Rotor Characteristics

Abstract

The present invention relates to a rotor slot design method based on the locked-rotor characteristics of a motor, belonging to the technical field of motors, and solves the technical problems that the existing single rotor slot type cannot achieve the matching of the starting performance of the motor with the working conditions and has poor economic benefits. The solution is as follows: A rotor slot design method based on the locked-rotor characteristics of a motor includes the following steps: 1) Design a first rotor slot type and a second rotor slot type. The shapes of the first rotor slot type and the second rotor slot type are the same. The br1 of the first rotor slot type is greater than the br1' of the second rotor slot type, and the br2 of the first rotor slot type is greater than the br2' of the second rotor slot type; 2) When the motor is at the first gear power, select the situation closest to the standard locked-rotor current as the rotor punching slot type; 3) When the motor is at the second, third, fourth, and fifth gear powers, the rotor punching is arranged in a combination of different numbers and different arrangements of a plurality of first rotor slot types and second rotor slot types, and the rotor punching slot type is selected with the optimal locked-rotor current as the target.

Description

Technical Field

[0001] The present invention belongs to the technical field of motors, and particularly relates to a rotor slot design method based on the locked-rotor characteristics of motors. Background Art

[0002] The rotor slot has an important influence on the performance of the motor. Changing the cage rotor slot and related dimensions can cause the starting performance of the motor to vary within a large range. Under the condition that the stator design remains unchanged, appropriate changes to the rotor slot can obtain better starting performance. To measure the starting performance of the motor, the quality factor Kst is generally used. The quality factor Kst is calculated as the ratio of the locked-rotor torque Tst to the locked-rotor current Ist, that is, Kst = Tst / Ist. When Ist is controlled within a reasonable range, the larger the quality factor, the more the motor can adapt to severe starting requirements. As known from electrical machinery, the locked-rotor torque Tst ∝ r2s / Zst 2 , and the locked-rotor current Ist ∝ 1 / Zst, where Zst is the total impedance during starting and r2s is the rotor starting resistance.

[0003] Currently, for low-voltage high-power cage rotor motors with the same frame number and the same number of poles but different powers, in order to ensure the universality of the mold, the same rotor slot is used. However, for low-voltage high-power motors with the same center height and the same number of poles, the power range span is relatively large, generally exceeding 5 power grades. The electromagnetic design is carried out under the conditions of equal-proportion iron length and isothermal rise boundary conditions. As the power and iron length increase, the rotor starting resistance r2s remains basically unchanged, while the stator resistance r1, the stator end leakage reactance Xe1 during starting, and the rotor end leakage reactance Xe2 during starting gradually decrease, resulting in a decrease in the total impedance Zst during starting, and further leading to a significant increase in the locked-rotor torque Tst and the locked-rotor current Ist. This causes the problems that the locked-rotor torque Tst and the locked-rotor current Ist of small-power specifications are too small, and the locked-rotor torque Tst and the locked-rotor current Ist of large-power specifications are too large. With the increasing market demand for high-efficiency low-voltage high-power motors, in the face of different application conditions, customers have different requirements for the locked-rotor current and the locked-rotor torque of motors of the same specification. A single rotor slot shape cannot achieve the matching of the motor starting performance with all operating conditions, and it is necessary to customize motors for different conditions according to the load and application scenarios, resulting in an increase in the number of molds and poor economic benefits. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art and solve the technical problems such as the inability of the existing single rotor slot to match the motor starting performance with the working conditions and poor economic benefits, the present invention provides a rotor slot design method based on the locked-rotor characteristics of the motor.

[0005] The present invention is achieved through the following technical solutions.

[0006] The present invention provides a rotor slot design method based on the locked-rotor characteristics of a motor. The motors have the same center height and the same number of poles. The motors include a first power rating, a second power rating, a third power rating, a fourth power rating, and a fifth power rating from small to large. The motor is a 315-frame two-pole motor. The first power rating is 110 kW, the second power rating is 132 kW, the third power rating is 160 kW, the fourth power rating is 185 kW, and the fifth power rating is 200 kW. The method includes the following steps:

[0007] 1) Design a first rotor slot and a second rotor slot. The shapes of the first rotor slot and the second rotor slot are the same. The br1 of the first rotor slot is greater than br1' of the second rotor slot, and the br2 of the first rotor slot is greater than br2' of the second rotor slot;

[0008] 2) When the motor is at the first power rating, the rotor punching sheet is evenly distributed with a certain number of the first rotor slots and a certain number of the second rotor slots in two cases. Calculate the quality factor and the locked-rotor current when the motor operates in the two cases, and select the case with the locked-rotor current closest to the standard as the rotor punching sheet slot type, and the locked-rotor current is the optimal locked-rotor current;

[0009] 3) When the motor is at the second power rating, the third power rating, the fourth power rating, and the fifth power rating, the rotor punching sheet is arranged in a combination of different numbers and different permutations of a certain number of the first rotor slots and the second rotor slots. Calculate the quality factor and the locked-rotor current when the motor operates in the combination of different numbers and different permutations, and select the rotor punching sheet slot type with the optimal locked-rotor current obtained in step 2) as the target.

[0010] Further, both the first rotor slot and the second rotor slot include an arc edge, two upper opposite side edges, two upper parallel straight edges, two lower opposite side edges, and a lower parallel straight edge. The arc edge is connected to the two upper opposite side edges. The two upper opposite side edges are inclined outward relative to the arc edge. The two upper opposite side edges are connected to the two upper parallel straight edges. The two upper parallel straight edges are connected to the two lower opposite side edges. The two lower opposite side edges are inclined inward relative to the upper parallel straight edges. The two lower opposite side edges are respectively connected to the lower parallel straight edge.

[0011] Further, the size of br1 of the first rotor slot is 1.5 mm, and the size of br2 of the first rotor slot is 3.0 mm; the size of br1' of the second rotor slot is 1.0 mm, and the size of br2' of the second rotor slot is 2.7 mm.

[0012] Further, when the motor is at the first power rating of 110 kW, the rotor punching sheet slot type is that the rotor punching sheet is evenly distributed with 40 first rotor slots, and the optimal locked-rotor current is 7.0.

[0013] Further, when the motor is at the second gear power of 132 kW, the rotor punching slot type selected with the optimal locked-rotor current as the target is a combination of 24 first rotor slot types and 16 second rotor slot types.

[0014] Further, when the motor is at the third gear power of 160 kW, the rotor punching slot type selected with the optimal locked-rotor current as the target is a combination of 16 first rotor slot types and 24 second rotor slot types.

[0015] Further, when the motor is at the fourth gear power of 185 kW, the rotor punching slot type selected with the optimal locked-rotor current as the target is a combination of 8 first rotor slot types and 32 second rotor slot types.

[0016] Further, when the motor is at the fifth gear power of 200 kW, the rotor punching slot type selected with the optimal locked-rotor current as the target is that 40 second rotor slots are evenly distributed on the rotor punching.

[0017] The beneficial effects achieved by the present invention are as follows: The present invention proposes a rotor slot type design method for improving the locked-rotor characteristics of motors with different powers but the same center height and the same number of poles. The first rotor slot type and the second rotor slot type are designed. The shapes of the first rotor slot type and the second rotor slot type are the same. The br1 of the first rotor slot type is greater than the br1' of the second rotor slot type, and the br2 of the first rotor slot type is greater than the br2' of the second rotor slot type. The sizes of br1 and br2 mainly affect the rotor slot leakage reactance Xs2s and the rotor starting resistance r2s during motor starting. The smaller br1 and br2 are, the larger the rotor slot leakage reactance Xs2s and the rotor starting resistance r2s are during starting. The total impedance Zst during starting increases, and the increase in the total impedance Zst during starting is much larger than that of the rotor starting resistance r2s. Therefore, the locked-rotor torque Tst and the locked-rotor current Ist decrease. In this way, the locked-rotor torque Tst and the locked-rotor current Ist of the first rotor slot type are both larger than those of the second rotor slot type; the settings of different numbers and different permutation and combination methods of the first rotor slot type and the second rotor slot type on the rotor punching. The more the first rotor slot type, the larger the locked-rotor torque Tst and the locked-rotor current Ist. The more the second rotor slot type, the smaller the locked-rotor torque Tst and the locked-rotor current Ist. Through the design of the double rotor slots of the first rotor slot type and the second rotor slot type, the unreasonable locked-rotor characteristics of the motor brought by a single rotor slot type are avoided, and the problem of the increase in molds and poor economic benefits caused by customizing motors for different customers in different loads and application scenarios is solved; in addition, through the design of the double rotor slots of the present invention, an idea can also be inspired to design multiple rotor slots. According to the method of the present invention, several rotor slots are designed. Through the settings of different numbers and different permutation and combination methods of the several rotor slots, the rotor punching slot type selected with the optimal locked-rotor current as the target is realized at different powers.

[0018] Compared with the prior art, the present invention has the advantages of designing double rotor slots to match the motor starting performance with the working conditions and improving economic benefits. Description of the Drawings

[0019] Figure 1 is a schematic structural diagram of the first rotor slot type in the present invention;

[0020] Figure 2 is a schematic structural diagram of the second rotor slot type in the present invention;

[0021] Figure 3 is a schematic structural diagram of the rotor punching slot type when the motor is at the first gear power of 110 kW in the present invention;

[0022] Figure 4 is a schematic structural diagram of the rotor punching slot type selected with the optimal locked-rotor current as the target when the motor is at the second gear power of 132 kW in the present invention;

[0023] Figure 5 is a schematic structural diagram of the rotor punching slot type selected with the optimal locked-rotor current as the target when the motor is at the third gear power of 160 kW in the present invention;

[0024] Figure 6 is a schematic structural diagram of the rotor punching slot type selected with the optimal locked-rotor current as the target when the motor is at the fourth gear power of 185 kW in the present invention;

[0025] Figure 7 is a schematic structural diagram of the rotor punching slot type selected with the optimal locked-rotor current as the target when the motor is at the fifth gear power of 200 kW in the present invention.

[0026] In the figure: 1. First rotor slot type; 2. Second rotor slot type; 3. Arc edge; 4. Upper opposite side; 5. Upper parallel straight edge; 6. Lower opposite side; 7. Lower parallel straight edge. Detailed Description of the Invention

[0027] The present invention will be further described in detail below with reference to the drawings and embodiments.

[0028] As Figures 1 to 7 shown, a rotor slot type design method based on the locked-rotor characteristics of the motor, the motors have the same center height and the same number of poles, the motors include a first gear power, a second gear power, a third gear power, a fourth gear power, and a fifth gear power from small to large. In this embodiment, the motor is a center height 315 two-pole motor, the first gear power is 110 kW, the second gear power is 132 kW, the third gear power is 160 kW, the fourth gear power is 185 kW, and the fifth gear power is 200 kW, and the method includes the following steps:

[0029] 1) Design the first rotor slot type 1 and the second rotor slot type 2. The shapes of the first rotor slot type 1 and the second rotor slot type 2 are the same. The br1 of the first rotor slot type 1 is greater than br1' of the second rotor slot type 2, and the br2 of the first rotor slot type 1 is greater than br2' of the second rotor slot type 2. The other dimensions are the same. The sizes of br1 and br2 mainly affect the rotor slot leakage reactance Xs2s and the rotor starting resistance r2s during motor starting. The smaller br1 and br2 are, the greater the rotor slot leakage reactance Xs2s and the rotor starting resistance r2s are during starting. The total impedance Zst during starting increases, and the increase in the total impedance Zst during starting is much greater than that of the rotor starting resistance r2s. Therefore, the locked-rotor torque Tst and the locked-rotor current Ist decrease. Thus, the locked-rotor torque Tst and the locked-rotor current Ist of the first rotor slot type 1 are greater than those of the second rotor slot type 2;

[0030] Both the first rotor slot type 1 and the second rotor slot type 2 include an arc edge 3, two upper opposite side edges 4, two upper parallel straight edges 5, two lower opposite side edges 6, and a lower parallel straight edge 7. The arc edge 3 is connected to the two upper opposite side edges 4. The two upper opposite side edges 4 are inclined outward relative to the arc edge 3. The two upper opposite side edges 4 are connected to the two upper parallel straight edges 5. The two upper parallel straight edges 5 are connected to the two lower opposite side edges 6. The two lower opposite side edges 6 are inclined inward relative to the upper parallel straight edges 5. The two lower opposite side edges 6 are respectively connected to the lower parallel straight edge 7.

[0031] In this embodiment, the size of br1 of the first rotor slot type 1 is 1.5 mm, and the size of br2 of the first rotor slot type 1 is 3.0 mm; the size of br1' of the second rotor slot type 2 is 1.0 mm, and the size of br2' of the second rotor slot type 2 is 2.7 mm. Thus, the area of the first rotor slot type 1 can completely cover the area of the second rotor slot type 2, and the locked-rotor torque Tst and the locked-rotor current Ist of the first rotor slot type 1 are greater than those of the second rotor slot type 2;

[0032] 2) When the motor is at the first gear power, there are two cases where the rotor punching sheet is evenly distributed with a number of the first rotor slot types 1 and a number of the second rotor slot types 2. Calculate the quality factor and the locked-rotor current during the operation of the motor in the two cases, and select the case with the locked-rotor current closest to the standard as the rotor punching sheet slot type, and the locked-rotor current is the optimal locked-rotor current;

[0033] In this embodiment, when the motor is at the first gear power of 110 kW, the rotor punching sheet is evenly distributed with 40 first rotor slot types 1 and 40 second rotor slot types 2. When the rotor punching sheet is evenly distributed with 40 first rotor slot types 1, the quality factor Kst of the motor is 2.12 / 7.04 = 0.30, and the locked-rotor current Ist is 7.04. When the rotor punching sheet is evenly distributed with 40 second rotor slot types 2, the quality factor Kst of the motor is 1.97 / 6.16 = 0.32, and the locked-rotor current is 6.16. Generally speaking, the standard locked-rotor current is generally around 7. Therefore, compared with the standard locked-rotor current, the closest situation is that the rotor punching sheet is evenly distributed with 40 first rotor slot types 1, and the optimal locked-rotor current is 7.0;

[0034] 3) When the motor is at the second gear power, the third gear power, the fourth gear power, and the fifth gear power, the rotor punching sheet is arranged in a combination of different numbers and different permutations of a number of first rotor slot types 1 and second rotor slot types 2. Calculate the quality factor and the locked-rotor current of the motor when it operates in the combination of different numbers and different permutations, and select the rotor punching sheet slot type with the optimal locked-rotor current obtained in step 2) as the target.

[0035] When the motor is at the second gear power of 132 kW, the first rotor slot type 1 and the second rotor slot type 2 are arranged in a combination of different numbers and different permutations on the rotor punching sheet. Through the target of the optimal locked-rotor current of 7.0, the rotor punching sheet slot type is finally obtained as a combination of 24 first rotor slot types 1 and 16 second rotor slot types 2. The quality factor Kst of the motor is 2.28 / 7.06 = 0.32, and the locked-rotor current Ist is 7.06.

[0036] When the motor is at the third gear power of 160 kW, the first rotor slot type 1 and the second rotor slot type 2 are arranged in a combination of different numbers and different permutations on the rotor punching sheet. Through the target of the optimal locked-rotor current of 7.0, the rotor punching sheet slot type is finally obtained as a combination of 16 first rotor slot types 1 and 24 second rotor slot types 2. The quality factor Kst of the motor is 2.42 / 7.12 = 0.34, and the locked-rotor current Ist is 7.12.

[0037] When the motor is at the fourth gear power of 185 kW, the first rotor slot type 1 and the second rotor slot type 2 are arranged in a combination of different numbers and different permutations on the rotor punching sheet. Through the target of the optimal locked-rotor current of 7.0, the rotor punching sheet slot type is finally obtained as a combination of 8 first rotor slot types 1 and 32 second rotor slot types 2. The quality factor Kst of the motor is 2.44 / 6.99 = 0.35, and the locked-rotor current Ist is 6.99.

[0038] When the motor is at the fifth gear power of 200 kW, different numbers and different permutations and combinations of the first rotor slot type 1 and the second rotor slot type 2 are combined and set on the rotor punching sheet. Through the goal of the optimal locked-rotor current of 7.0, the rotor punching sheet slot type is finally obtained as 40 second rotor slot types 2 evenly distributed on the rotor punching sheet. The quality factor Kst of the motor is 2.52 / 7.03 = 0.36, and the locked-rotor current Ist is 7.03.

[0039] In the present invention, different numbers and different permutation and combination methods of the first rotor slot type 1 and the second rotor slot type 2 are set on the rotor punching sheet. The more the first rotor slot type 1, the greater the locked-rotor torque Tst and the locked-rotor current Ist. The more the second rotor slot type 2, the smaller the locked-rotor torque Tst and the locked-rotor current Ist. Through the design of the double rotor slots of the first rotor slot type 1 and the second rotor slot type 2, the unreasonable locked-rotor characteristics of the motor caused by a single rotor slot type are avoided, and the problem of increasing the number of molds and poor economic benefits brought by customizing motors for different customers in different loads and application scenarios is solved. In addition, through the design of the double rotor slots of the present invention, an idea can also be inspired to design multiple rotor slots. According to the method of the present invention, several rotor slots are designed, and through the setting of different numbers and different permutation and combination methods of the several rotor slots, the rotor punching sheet slot type is selected with the optimal locked-rotor current as the goal at different powers.

[0040] The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, the embodiments can still be changed. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A rotor slot design method based on the stall characteristics of a motor, wherein the motors have the same center height and the same number of poles, and the motors include a first gear power, a second gear power, a third gear power, a fourth gear power and a fifth gear power from small to large, characterized in that: The motor is a 315 center high two-pole motor, the first gear power is 110kW, the second gear power is 132kW, the third gear power is 160kW, the fourth gear power is 185kW, and the fifth gear power is 200kW, comprising the following steps: 1) designing a first rotor slot type (1) and a second rotor slot type (2), wherein the first rotor slot type (1) and the second rotor slot type (2) have the same shape, br1 of the first rotor slot type (1) is greater than br1' of the second rotor slot type (2), and br2 of the first rotor slot type (1) is greater than br2' of the second rotor slot type (2); 2) When the motor is in the first power level, the rotor laminations are evenly distributed with a plurality of first rotor slot types (1) and a plurality of second rotor slot types (2), and the quality factor and the stall current of the motor when running in the two cases are calculated. The stall current closest to the standard is selected as the rotor lamination slot type, and the stall current is the optimal stall current; 3) When the motor is in the second power gear, the third power gear, the fourth power gear and the fifth power gear, the rotor punching is arranged by combining different numbers and different arrangements and combinations of the first rotor slot type (1) and the second rotor slot type (2), and the quality factor and the stall current of the motor when running in the different numbers and different arrangements and combinations are calculated, and the rotor punching slot type is selected with the optimal stall current obtained in step 2) as the target.

2. The rotor slot design method based on motor stall characteristics according to claim 1 is characterized in that: The first rotor slot type (1) and the second rotor slot type (2) both comprise an arc edge (3), two upper opposite side edges (4), two upper parallel straight edges (5), two lower opposite side edges (6) and a lower parallel straight edge (7); the arc edge (3) is connected to the two upper opposite side edges (4); the two upper opposite side edges (4) are inclined outwardly relative to the arc edge (3); the two upper opposite side edges (4) are connected to the two upper parallel straight edges (5); the two upper parallel straight edges (5) are connected to the two lower opposite side edges (6); the two lower opposite side edges (6) are inclined inwardly relative to the upper parallel straight edges (5); and the two lower opposite side edges (6) are respectively connected to the lower parallel straight edges (7).

3. The rotor slot design method based on motor stall characteristics according to claim 2 is characterized in that: The size of br1 of the first rotor slot type (1) is 1.5 mm, and the size of br2 of the first rotor slot type (1) is 3.0 mm; the size of br1' of the second rotor slot type (2) is 1.0 mm, and the size of br2' of the second rotor slot type (2) is 2.7 mm.

4. The rotor slot design method based on motor stall characteristics according to claim 3 is characterized in that: When the motor is in the first gear with a power of 110 kW, the rotor punching slot type is 40 first rotor slot types (1) evenly distributed on the rotor punching slots, and the optimal locked-rotor current is 7.

0.

5. The rotor slot design method based on motor stall characteristics according to claim 3 is characterized in that: When the motor is in the second gear with a power of 132 kW, the rotor punching slot type selected as the target for the optimal stall current is a combination of 24 first rotor slot types (1) and 16 second rotor slot types (2).

6. The rotor slot design method based on motor stall characteristics according to claim 3 is characterized in that: When the motor is in the third gear with a power of 160 kW, the rotor punching slot type selected with the optimal locked-rotor current as the target is a combination of 16 first rotor slot types (1) and 24 second rotor slot types (2).

7. The rotor slot design method based on motor stall characteristics according to claim 3 is characterized in that: When the motor is in the fourth gear with a power of 185 kW, the rotor punching slot type selected with the optimal stall current as the target is a combination of 8 first rotor slot types (1) and 32 second rotor slot types (2).

8. The rotor slot design method based on motor stall characteristics according to claim 3 is characterized in that: When the motor is in the fifth gear with a power of 200 kW, the rotor slot type selected with the optimal locked-rotor current as the target is the second rotor slot type (2) with 40 rotor slots evenly distributed.

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