CN110994926B - A method for avoiding the breakage of the rotor end of a high-voltage and high-power squirrel motor - Google Patents

Abstract

The invention discloses a rotor end of a high-voltage and high-power cage-type motor, comprising an end section of a segmented iron core, an end ring and a bar end with stress concentration alleviation properties, and the bar end with stress concentration relief properties The upper plane of the iron core adopts a four-step structure connected by an arc surface. The guide bar in the end section of the segmented iron core is the first step structure of the arc surface, and the guide bar welded in the end ring is the fourth step structure of the arc surface. The guide bar from the end face of the iron core to the welding surface of the end ring is the second step structure of the arc surface and the third step structure of the arc surface. By optimizing the shape of the stress concentration part at the end of the bar, the stress between the low stress area and the high stress area can achieve a smooth transition, which greatly improves the problem of stress concentration, and can effectively avoid the rotor end of the cage motor caused by frequent starting. The phenomenon of fracture between the bar and the end ring caused by excessive stress concentration.

Description

A method for avoiding the breakage of the rotor end of a high-voltage and high-power squirrel motor

technical field

The invention belongs to the technical field of motor design and manufacture, and particularly relates to a rotor end of a high-voltage and high-power cage-type motor, which avoids the problem that the end of the cage-type motor is broken.

Background technique

The rotor of high-voltage and high-power motors mostly adopts cage-type copper bar structure. In actual operation, due to various reasons, high-voltage and high-power motors are prone to breakage at the end of the rotor copper bar. posed a serious threat to the safe operation of

The main reasons for the fracture of the rotor copper bars are as follows:

1) The guide bar is not tight enough in the rotor core. In actual production, the bar cannot be absolutely fastened in the rotor core. At this time, the bar will be subjected to various forces such as thermal bending deflection force, radial electromagnetic force, centrifugal force of the bar itself, and circumferential electromotive force. Not only is the force complex, but also the cross-section of the two welded bars is prone to fatigue fracture under the combined action of these forces.

2) The motor starts for a long time and starts frequently. When the motor starts, the force on the rotor bar can be regarded as a non-periodically changing alternating force, and during the motor starting process, the alternating and temperature rise of thermal stress caused by the skin effect of the bar is accelerated. These can easily lead to the fracture of the welded joint between the bar and the end ring.

3) The reason for welding. Due to local heating, the temperature change range on the weldment is large and uneven. When the temperature of the solder decreases, in addition to causing changes in the structure and properties of the weld, it will also cause uneven shrinkage and expansion of the material, resulting in conductive The bar and the end ring generate internal stress and deformation, and in severe cases, small cracks will appear at the welding joint, which will lay hidden dangers for the fracture of the bar.

4) Stress concentration at the end of the bar. Under normal circumstances, in order to place the bar into the end ring groove, the end of the bar needs to be machined to a certain size, and the cross-sectional shape of the bar often changes abruptly at the machining place. The edges and corners of the bar will cause stress concentration. When the motor is running, due to the combined effect of the above three reasons, the bar will be broken directly at the stress concentration.

Therefore, trying to avoid or improve the stress concentration at the end of the bar can effectively improve the fatigue strength of the end of the rotor, and reduce and eliminate the probability of fracture of the copper bar of the rotor. At present, the methods to improve stress concentration mainly include: improving the surface processing quality of copper bars and end rings; using additional components such as guard rings to eliminate alternating forces; Although the stress concentration of the bar is improved to a certain extent, a sudden change in the cross-sectional shape is still formed at the processing of the end of the bar. How to optimize the shape of the stress concentration part at the end of the bar, so that the stress between the low stress area and the high stress area can achieve a smooth transition, so as to improve the problem of stress concentration at the end of the bar, and then avoid the end of the cage motor rotor. phenomenon, these problems are the technical problems to be solved by the present invention.

SUMMARY OF THE INVENTION

Aiming at how to optimize the shape of the stress concentration part at the end of the bar, the stress between the low stress area and the high stress area can be smoothly transitioned, so as to improve the stress concentration at the end of the bar and avoid the fracture of the end of the cage motor rotor. Problem, in order to solve the above technical problems, the present invention proposes a rotor end of a high-voltage and high-power squirrel cage motor.

In order to achieve the above purpose, the technical scheme adopted in the present invention is:

A cage-type motor rotor end, comprising: an end section 1 of a segmented iron core, an end ring 3 and a bar end 2 with stress concentration alleviation properties, the bar end 2 with stress concentration alleviation properties The upper plane of the iron core adopts a four-step structure connected by an arc surface. The guide bar in the end section 1 of the segmented core is the first step structure of the arc surface, and the guide bar welded in the end ring 3 is the fourth step structure of the arc surface. , the bar extending from the end face of the iron core to the welding surface of the end ring 3 is the second step structure of the arc surface and the third step structure of the arc surface. .

On the basis of the above solution, the starting point of the first step structure of the arc surface is located at 1/2 to 3/4 of the end section 1 extending into the segmented iron core, and the end point is located at the end extending out of the segmented iron core 3mm to 5mm of segment 1.

On the basis of the above solution, the lengths of the horizontal planes of the second step structure of the camber surface and the third step structure of the camber surface are equal, and the starting point of the second step structure of the camber surface is the end point of the first step structure of the camber surface, so The end point of the second step structure of the arc surface is the starting point of the third step structure of the arc surface, and the end point of the third step structure of the arc surface is located at a distance of 3 mm to 5 mm from the welding surface of the end ring 3 .

On the basis of the above solution, the starting point of the cambered fourth stepped structure is the end point of the cambered third stepped structure, and the end point of the cambered fourth stepped structure is the end point of the bar.

On the basis of the above scheme, the upper plane of the bar end portion 2 with the characteristics of reducing stress concentration is determined by the following formula: the starting point of the first stepped structure of the arc surface is determined by the following formula: The horizontal line is the x-axis, and the vertical line is the y-axis.

Among them, when x takes the value [0, d ₁ ), y represents the curved surface part of the first step structure of the arc surface; when x takes the value [d ₁ , d ₁ +d ₀ ), y represents the first step structure of the arc surface _{The horizontal plane part of _ _ 2} , d ₁ +d ₀ +d ₂ +d ₃ ), y represents the horizontal part of the second step structure of the arc surface; when x takes the value [d ₁ +d ₀ +d ₂ +d ₃ ,d ₁ +d ₀ +d ₂ +d ₃ +d ₄ ), y represents the curved surface part of the third step structure of the arc surface; when x takes the value [d ₁ +d ₀ +d ₂ +d ₃ +d ₄ ,d ₁ +d ₀ + d ₂ +d ₃ +d ₄ +d ₅ ), y represents the horizontal part of the third step structure of the arc surface; when x takes the value [d ₁ +d ₀ +d ₂ +d ₃ +d ₄ +d ₅ ,d ₁ +d ₀ +d ₂ +d ₃ +d ₄ +d ₅ +d ₆ ), y represents the curved surface part of the fourth step structure of the arc surface; when x takes the value [d ₁ +d ₀ +d ₂ +d ₃ +d ₄ +d ₅ +d ₆ ,d ₁ +d ₀ +d ₂ +d ₃ +d ₄ +d ₅ +d ₆ +d ₇ ], y represents the horizontal part of the fourth step structure of the arc surface; the The height of the first stepped structure of the arc surface is h ₁ , the value of h ₁ is 0.5-1.5 mm, the length of the arc surface is d ₁ , and the length of the horizontal plane of the stepped surface is d ₀ ; the height of the second stepped structure of the arc surface is h ₂ , h ₂ is 1-2 mm, the length of the arc surface is d ₂ , and the length of the horizontal surface of the stepped surface is d ₃ ; the height of the third step structure of the arc surface is h ₃ , the value of h ₃ is 1-2 mm, The length is d ₄ , the length of the horizontal plane of the stepped surface is d ₅ ; the height of the fourth step structure of the arc surface is h ₄ , and h ₄ is 1-2 mm, the length of the arc surface is d ₆ , and the length of the horizontal plane of the stepped surface is d ₇ .

On the basis of the above scheme, the starting point of the concave surface is located at 1/2 to 3/4 of the end section 1 extending into the segmented iron core, and the end point of the concave surface is located at 3 mm from the end section 1 extending into the segmented iron core. ~5mm.

On the basis of the above solution, the shape of the concave surface is determined by the following formula: take the starting point of the concave surface as the origin, take the horizontal line of the bar as the x-axis, and the vertical vertical line as the y-axis,

Among them, when x takes the value [0, d ₈ ), y represents the curved part of one end of the concave surface; when x takes the value [d ₈ , d ₈ +d ₉ ), y represents the horizontal plane part of the concave surface, and when x takes the value [ d ₈ +d ₉ , 2×d ₈ +d ₉ ), y represents the curve part at the other end of the concave surface, d ₈ is the horizontal length corresponding to the arc surfaces at both ends of the concave surface; d ₉ is the length of the horizontal surface of the concave surface; h ₅ is The depth of the concave surface, its value is 0.5 ~ 1.5mm.

On the basis of the above scheme, ventilation slots 4 are arranged between each section of the iron core.

The beneficial effects of the present invention are:

(1) Using the rotor end of the high-voltage and high-power cage type motor proposed by the present invention, a gap of 1 to 3 mm is left between the iron core groove of the iron core end section and the upper and lower bars of the guide bar, which increases the length of the bar protruding from the iron core in disguise , reducing the welding stress between the bar and the end ring, and eliminating the stress concentration point where the bar and the end face of the iron core meet.

(2) Using the rotor end of the high-voltage and high-power cage motor proposed by the present invention, the cross-section of the end of the bar changes gradually, and there is a curved surface to greatly disperse the stress concentration, so that the low-stress area and the high-stress area are separated. The stress between them achieves a smooth transition, avoiding the breakage of the rotor end caused by the uneven stress caused by the rapid change of the cross-section of the bar placed in the end ring groove and the cross-section of the bar placed in the core.

(3) Using the rotor end of the high-voltage and high-power cage type motor proposed by the present invention, the stator and rotor core of the motor are not changed, and the parts such as the rotor end ring guard ring are not changed, but the shape of the end of the bar is changed. , has the advantages of simple operation and low cost.

Description of drawings

The present invention has the following accompanying drawings:

FIG. 1 is a schematic diagram of the rotor end proposed in the present invention.

Figure 2 is a detailed dimension drawing of the concave surface and the cambered surface steps at the end of the rotor.

Figure 3 is a schematic diagram of the end of a conventional bar.

Fig. 4 Comparison of the stress distribution on the bottom surface of the conventional bar and the bar of the present invention during load operation.

FIG. 5 is a comparison of the stress distribution on the top surface of the conventional bar and the bar of the present invention during load operation.

Description of reference numerals: 1-end section of segmented core; 2-bar end with stress concentration relief properties; 3-end ring; 4-vent slot; 5-conventional bar end.

Detailed ways

The present invention will be further described in detail below in conjunction with accompanying drawings 1-5.

The invention provides a rotor end of a high-voltage and high-power cage type motor. A gap of 1-3 mm is left between the iron core groove of the iron core end section and the upper and lower bars of the guide bar, which increases the length of the bar protruding from the iron core in a disguised form and reduces the The welding stress between the bar and the end ring eliminates the stress concentration point where the bar and the end face of the iron core are connected; the cross section of the end of the bar changes gradually, and there is a curved surface to greatly disperse the stress concentration, The stress between the low stress area and the high stress area is smoothly transitioned, avoiding the rotor end caused by the uneven stress caused by the rapid change of the cross section of the bar placed in the end ring groove and the cross section of the bar placed in the core fracture.

Example:

Taking a 1600kW squirrel-cage asynchronous motor as an example, according to the rotor end of the motor provided by the present invention, the specific dimensions of the bar end 2 with the characteristics of alleviating stress concentration are determined as follows: d ₀ =39mm; d ₁ =2mm; d ₂ =3mm; _d3 =12mm; _d4 =3mm; d5=12mm _; d6=3mm _{; d7} =15mm; _d8 =2mm; _d9 =39mm; _h1 =0.7mm; h2= _2mm ; h ₃ =2mm; h ₄ =1.5mm; h ₅ =0.7mm, the meaning of the specific dimension of the bar end is shown in Figure 2, the total length of the bar is 700mm, the length of the bar extending from the core is 60mm, and the bar is inserted The inner length of the welding groove of the end ring 3 is 6mm.

Figure 3 shows the structure of the 1600kW squirrel-cage asynchronous motor using a conventional bar end 5. It can be seen from the comparison between Figure 1 and Figure 3 that the bar end 2 with the characteristics of reducing stress concentration proposed by the present invention has a The cross-sectional area changes gently, and the length of the bar protruding from the core is increased in disguised form. These structures can improve the stress concentration at the end of the bar.

Figure 4 is a comparison of the stress distribution on the bottom surface of the conventional bar and the bar of the present invention when the load is running. It can be seen from Figure 4 that when the motor using the end structure of the conventional bar is running under load, the bottom of the bar and the The stress at the end face of the rotor core is relatively large, and the maximum is about 160MPa. However, when the motor using the guide bar for preventing rotor end breakage proposed by the present invention is running under load, since there is a gap between the upper and lower surfaces of the guide bar and the iron core, the guide bar does not contact the end surface of the iron core, which greatly reduces the problem of stress on the bar.

Figure 5 is a comparison of the stress distribution on the top surface of the conventional bar and the bar of the present invention when the load is running. It can be seen from Figure 5 that when the motor using the conventional bar end structure is running under load, in order to make the guiding The bar can be easily inserted into the end ring groove, and the upper surface of the bar is beveled, resulting in a sudden change in the cross-section of the bar, causing stress to concentrate here, where the maximum stress reaches 136MPa; The stress concentration at the welding point of the bar and the end ring is the largest, and the maximum stress value reaches nearly 170MPa. Generally, the end of the bar fracture occurs here. When the motor using the guide bar for preventing rotor end breakage proposed by the present invention is running under load, the cross section of the end of the guide bar changes gradually and has a curved surface to greatly disperse the stress concentration, so that the low stress area and the high stress area are formed. The stress between them achieves a smooth transition, which greatly avoids the uneven stress caused by the rapid change of the cross-section of the bar placed in the end ring groove and the cross-section of the bar placed in the iron core. In the guide bar for preventing the end of the rotor from breaking, the maximum stress at the welding place between the guide bar and the end ring is 136MPa, which greatly alleviates the problem of stress concentration.

To sum up, the rotor end of a high-voltage and high-power cage motor proposed by the present invention can effectively improve the stress concentration of the end 5 of the conventional bar, so that the stress between the low-stress area and the high-stress area can achieve a smooth transition. , to eliminate the stress unevenness caused by the rapid change of the section of the bar placed in the end ring groove and the section of the bar placed in the core, and, due to the use of the structure of the cantilever beam of the increased bar, the bar and the end are further reduced. The stress at the ring weld is limited by the above technical features to avoid the occurrence of rotor end fracture.

Contents not described in detail in this specification belong to the prior art known to those skilled in the art.

Claims (4)

1. A cage-type motor rotor end, characterized in that it comprises: an end section (1) of a segmented iron core, an end ring (3) and a bar end (2) with the characteristics of reducing stress concentration, so The upper plane of the bar end (2) with the characteristics of alleviating stress concentration adopts a four-step structure connected by an arc surface, and the bar in the end section (1) of the segmented core is the first step structure of the arc surface, The guide bar welded in the end ring (3) is an arc surface fourth stepped structure, and the guide bar extending from the end face of the iron core to the welding surface of the end ring (3) is an arc surface second stepped structure and an arc surface third stepped structure in turn. , the lower plane of the bar end (2) with the characteristic of alleviating stress concentration adopts a concave design; The starting point of the first step structure of the arc surface is located at 1/2 to 3/4 of the end section (1) extending into the segmented iron core, and the end point is located at the end of the end section (1) extending into the segmented iron core. 3mm～5mm; The lengths of the horizontal planes of the second step structure of the arc surface and the third step structure of the arc surface are the same, the starting point of the second step structure of the arc surface is the end point of the first step structure of the arc surface, and the second step structure of the arc surface is the end point of the first step structure of the arc surface. The end point of the arc surface third stepped structure is the starting point of the arc surface third stepped structure, and the end point of the arc surface third stepped structure is located at a distance of 3 mm to 5 mm from the welding surface of the end ring (3); The starting point of the fourth step structure of the arc surface is the end point of the third step structure of the arc surface, and the end point of the fourth step structure of the arc surface is the end point of the guide bar; The upper plane of the bar end portion (2) with the characteristic of alleviating stress concentration adopts a four-step structure connected by an arc surface and is determined by the following formula: take the starting point of the first step structure of the arc surface as the origin, and take the horizontal line of the bar as the x-axis , the vertical line is the y-axis,

Among them, when x takes the value [0, d ₁ ), y represents the curved surface part of the first step structure of the arc surface; when x takes the value [d ₁ , d ₁ +d ₀ ), y represents the first step structure of the arc surface _{The horizontal plane part of _ _ 2} , d ₁ +d ₀ +d ₂ +d ₃ ), y represents the horizontal part of the second step structure of the arc surface; when x takes the value [d ₁ +d ₀ +d ₂ +d ₃ ,d ₁ +d ₀ +d ₂ +d ₃ +d ₄ ), y represents the curved surface part of the third step structure of the arc surface; when x takes the value [d ₁ +d ₀ +d ₂ +d ₃ +d ₄ ,d ₁ +d ₀ + d ₂ +d ₃ +d ₄ +d ₅ ), y represents the horizontal part of the third step structure of the arc surface; when x takes the value [d ₁ +d ₀ +d ₂ +d ₃ +d ₄ +d ₅ ,d ₁ +d ₀ +d ₂ +d ₃ +d ₄ +d ₅ +d ₆ ), y represents the curved surface part of the fourth step structure of the arc surface; when x takes the value [d ₁ +d ₀ +d ₂ +d ₃ +d ₄ +d ₅ +d ₆ ,d ₁ +d ₀ +d ₂ +d ₃ +d ₄ +d ₅ +d ₆ +d ₇ ], y represents the horizontal part of the fourth step structure of the arc surface; the The height of the first stepped structure of the arc surface is h ₁ , the value of h ₁ is 0.5-1.5 mm, the length of the arc surface is d ₁ , and the length of the horizontal plane of the stepped surface is d ₀ ; the height of the second stepped structure of the arc surface is h ₂ , h ₂ is 1～2mm, the length of the arc surface is d ₂ , the length of the horizontal plane of the stepped surface is d ₃ ; the height of the third step structure of the arc surface is h ₃ , the value of h ₃ is 1～2mm, the arc surface The length is d ₄ , the length of the horizontal plane of the stepped surface is d ₅ ; the height of the fourth step structure of the arc surface is h ₄ , and h ₄ is 1-2 mm, the length of the arc surface is d ₆ , and the length of the horizontal plane of the stepped surface is d ₇ . . 2 . The rotor end of the squirrel motor according to claim 1 , wherein the starting point of the concave surface is located at 1/2 to 3/4 of the end section ( 1 ) extending into the segmented iron core, and the concave surface The end point is located at 3mm to 5mm of the end section (1) extending out of the segmented iron core. 3 . The rotor end of the squirrel motor as claimed in claim 2 , wherein the shape of the concave surface is determined by the following formula: take the starting point of the concave surface as the origin, the horizontal line of the bar as the x-axis, and the vertical line as the y-axis,

Among them, when x takes the value [0, d ₈ ), y represents the curved part of one end of the concave surface; when x takes the value [d ₈ , d ₈ +d ₉ ), y represents the horizontal plane part of the concave surface, and when x takes the value [ d ₈ +d ₉ , 2×d ₈ +d ₉ ), y represents the curve part at the other end of the concave surface, d ₈ is the horizontal length corresponding to the arc surfaces at both ends of the concave surface; d ₉ is the length of the horizontal surface of the concave surface; h ₅ is The depth of the concave surface, its value is 0.5 ~ 1.5mm. 4. The rotor end of the squirrel motor according to claim 1, characterized in that ventilation slots (4) are provided between each section of the iron core.

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