CN110829769B - Rotor intermediate ring structure and design method thereof - Google Patents
Rotor intermediate ring structure and design method thereof Download PDFInfo
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- CN110829769B CN110829769B CN201911115278.2A CN201911115278A CN110829769B CN 110829769 B CN110829769 B CN 110829769B CN 201911115278 A CN201911115278 A CN 201911115278A CN 110829769 B CN110829769 B CN 110829769B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K17/00—Asynchronous induction motors; Asynchronous induction generators
- H02K17/02—Asynchronous induction motors
- H02K17/16—Asynchronous induction motors having rotors with internally short-circuited windings, e.g. cage rotors
- H02K17/165—Asynchronous induction motors having rotors with internally short-circuited windings, e.g. cage rotors characterised by the squirrel-cage or other short-circuited windings
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K15/00—Methods or apparatus specially adapted for manufacturing, assembling, maintaining or repairing of dynamo-electric machines
- H02K15/0012—Manufacturing cage rotors
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K2213/00—Specific aspects, not otherwise provided for and not covered by codes H02K2201/00 - H02K2211/00
- H02K2213/03—Machines characterised by numerical values, ranges, mathematical expressions or similar information
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Abstract
The invention discloses a rotor intermediate ring structure and a design method thereof, wherein the rotor intermediate ring structure comprises an intermediate ring body, and the axial height of the intermediate ring body is as follows: l. the IR ∈(0,l R /3]In the formula: l. the R Is the end ring axial height. The radial width of the intermediate ring body is: b is a mixture of IR ∈[3b t2 /4,(D 2 ‑D 0 +6b t2 )/8](ii) a A design method of a rotor intermediate ring structure comprises the following steps: determining the electric density range of the middle ring as J IR =(J R ‑J B ) (ii) a Determining a relation of current amplitude of the intermediate ring and obtaining an equivalent resistance expression of the rotor; estimating the amplitude of the intermediate ring current by the known conducting bar current of the rotor motor without the intermediate ring, and obtaining the range of the sectional area of the intermediate ring; the intermediate ring parameter at the minimum equivalent resistance is selected. The invention ensures that all parts of the rotor winding of the intermediate ring have uniform heat dissipation and reduces the loss of the rotor winding as much as possible on the basis of considering the actual processing condition of the rotor core.
Description
Technical Field
The invention relates to the technical field of design of cage type induction motors, in particular to a rotor intermediate ring structure and a design method thereof.
Background
The traditional cage type rotor winding consists of conducting bars and end rings, and the proper area of the conducting bars and the area of the end rings are ensured during the structural design of the motor. For a common cage-type cast aluminum rotor of a medium-and-small-sized motor, a conducting bar electric density J is usually taken B =(2.0-4.5)A/mm 2 End ring electrical density range J R =(0.45-0.8)J B . To ensure a sufficiently large starting torque, the rotor resistance needs to be sufficiently large, i.e. the corresponding electrical density cannot be too small; meanwhile, if the rotor density is too large, the larger rotor resistance will increase the extra rotor winding loss and will reduce the rotational speed of the motor during rated operation. If the rotor winding structure is not properly designed, the thermal stress caused by uneven heating of each part of the cage-type winding can cause cracks and even breakage of the conducting bars. The rotor broken bar fault can cause the distortion of the magnetic field of the motor, causing the multi-aspect of the motorPerformance deteriorates, for example, the output torque of the motor fluctuates, an additional electromagnetic force is generated to cause electromagnetic vibration, and the like.
The intermediate ring rotor winding consists of conducting bars, end rings and intermediate rings, and the design method of the end rings and the conducting bars in the rotor winding also needs to meet the design principle. However, since the intermediate ring is located at a specific position in the middle of the rotor winding, the current characteristics and the heat dissipation conditions of the intermediate ring are different from those of the end ring, and the design method is different, the research on the design method of the intermediate ring is still lacked.
Disclosure of Invention
The present invention is directed to solve the above problems and to provide a rotor intermediate ring structure and a method for designing the same, which can ensure uniform heat dissipation of each part of a rotor winding of the intermediate ring and minimize the loss of the rotor winding, in consideration of the actual processing condition of a rotor core.
The invention realizes the purpose through the following technical scheme:
a rotor intermediate ring structure comprises an intermediate ring body, wherein the axial height of the intermediate ring body is as follows: l. the IR ∈(0,l R /3]In the formula: l R Is the end ring axial height. The radial width of the intermediate ring body is: b IR ∈[3b t2 /4,(D 2 -D 0 +6b t2 )/8]In the formula: b t2 Height of rotor slots, D 2 Is the diameter of the outer circle of the rotor, D 0 The diameter of the inner circle of the rotor.
A design method of a rotor intermediate ring structure comprises the following steps:
step one, calculating the conducting bar electric density J when the corresponding motor adopts a single-chute rotor to operate B And end ring electrical seal J R Determining the electric density range of the intermediate ring as J IR =(J R -J B )。
And step two, determining a middle ring current amplitude relational expression according to the space distribution characteristics of the rotor current, and obtaining a rotor equivalent resistance expression. The amplitude of the intermediate ring current is estimated from the known bar currents of the rotor machine without the intermediate ring, and the range of the intermediate ring cross-sectional area is obtained.
The staggered distance of the upper rotor conducting bar and the lower rotor conducting bar is b st1 And b st2 Corresponding electrical angles are respectively beta 1 =pb st1 R and beta 2 =pb st2 R, wherein: p is the number of pole pairs of the motor, R is the radius of the rotor, Z 2 Is the number of rotor slots. The corresponding electrical angle of the rotor pitch is p2 pi/Z 2 It is obvious that the electrical angle relation α ═ β is satisfied 1 +β 2 。
If the stagger distances of the conducting bars are not equal, the conducting bars are b st1 ≠b st2 Through an odd number of intermediate ring currents I IR(2n-1) And even-order intermediate loop current I IR(2n) Phasor operation, upper bar current phasor I BU And lower conductor current phasor I BL Respectively expressed as:
upper side end ring current phasor of I RU The lower side end ring current phasor is I RL The bar current phasor may in turn be represented by the corresponding side end loop current phasor:
and subtracting the phasor of the upper and lower conducting bar currents on the two adjacent sides to obtain an expression of the intermediate loop current for odd times, and obtaining the expression of the intermediate loop current for even times by the same method.
The intermediate ring rotor is assumed to be a symmetrical rotor, i.e. the rotor cores have equal axial length l 1 =l 2 L, the sectional areas of the upper and lower conducting bars and the end ring are equal, so that the current amplitudes of the end rings at both ends are equal RU =I RL =I R The amplitude of the conducting bar current is equal to I BU =I BL =I B Since the bar current phasor is equal to the difference in the adjacent end ring current phasors on the corresponding side, the magnitude of the end ring current can be expressed as:
according to the phasor relation of the adjacent end ring currents, the intermediate ring current amplitude is respectively expressed as:
the amplitude component of each part of current in the rotor winding can be represented by the amplitude of conducting bar current, and the equivalent resistance R of the rotor 2 The joule loss consumed, equal to the sum of the joule losses consumed by the various portions of the rotor winding, can be expressed as:
wherein: r B Is a conducting bar resistance, Z 2 Is the number of rotor slots, R R Is the end ring segment resistance between adjacent conducting bars, the middle ring is staggered by a distance b st1 And b st2 The corresponding intermediate ring resistances are respectively R IR1 And R IR2 If the middle ring resistance in the range of the rotor pitch is R IR It is obvious thatSatisfy the relation R of the intermediate ring resistance IR1 +R IR2 =R IR 。
When the rotor winding is made of the same conductive material, the equivalent resistance of the rotor can be simplified as follows:
wherein: rho w Is the resistivity of the rotor winding, /) B For equivalent length of the conducting strip, D R ,D IR Average diameters of end rings and intermediate rings, A B ,A R And A IR Respectively the sectional areas of the conducting bar, the end ring and the intermediate ring, wherein the sectional area of the intermediate ring is equal to the product A of the axial height and the radial width of the intermediate ring IR =l IR ×b IR ,t 2 Is the pitch of the rotor, Z 2 Is the number of rotor slots, b st1 And b st2 The upper rotor conducting bar and the lower rotor conducting bar are staggered.
And thirdly, taking a plurality of numerical points within the radial width range, respectively determining the respective axial height range according to the sectional area range, calculating the resistance value of the equivalent rotor resistor, and selecting the intermediate ring parameter when the equivalent rotor resistor is the minimum.
The invention has the beneficial effects that:
1) the invention fills the blank of the design method of the rotor intermediate ring, not only considers the machining process, but also accords with the design principle of the motor;
2) the invention ensures the proper current density of the intermediate ring, and the heat dissipation of the rotor winding is uniformly distributed;
3) the invention ensures the proper axial height of the intermediate ring, the processing difficulty of the inner iron core is increased due to the over-small axial height, and the intermediate ring is difficult to be fully filled with aluminum liquid; the length of the equivalent iron core can be reduced due to too high axial height, and the iron core near the intermediate ring is easy to be distorted and deformed in the laminating process;
4) on the premise of meeting the requirement that all parts of the rotor winding are uniformly radiated, the equivalent resistance of the rotor is reduced, and therefore the winding loss of the running of the motor is reduced.
Drawings
FIG. 1 is a schematic view of an intermediate ring rotor winding according to the present invention;
FIG. 2 is a schematic diagram of an impedance network for an intermediate ring rotor winding in accordance with the present invention;
FIG. 3 is a schematic view of the structure of the rotor intermediate ring in the present invention;
FIG. 4 is a schematic diagram of the structure of the rotor winding portions of the intermediate ring of the present invention;
fig. 5 is a schematic view showing the structure of each part of an intermediate ring rotor core according to the present invention.
Detailed Description
The present application will now be described in further detail with reference to the drawings, it should be noted that the following detailed description is given for illustrative purposes only and is not to be construed as limiting the scope of the present application, as those skilled in the art will be able to make numerous insubstantial modifications and adaptations to the present application based on the above disclosure.
Fig. 3 shows a rotor intermediate ring structure, which includes an intermediate ring body, and the axial height of the intermediate ring body is: l IR ∈(0,l R /3]In the formula: l. the R Is the end ring axial height. The radial width of the intermediate ring body is: b is a mixture of IR ∈[3b t2 /4,(D 2 -D 0 +6b t2 )/8]In the formula: b is a mixture of t2 Height of rotor slots, D 2 Is the diameter of the outer circle of the rotor, D 0 Is the diameter of the inner circle of the rotor.
A design method of a rotor intermediate ring structure comprises the following steps:
step one, calculating the conducting bar electric density and the end ring electric density when the corresponding motor adopts a non-middle ring rotor to operate, and determining that the electric density range of a middle ring is J IR =(J R -J B )。
Table 1 shows the main parameters of a 25kW four-pole motor
Rated voltage (V) | 230 |
Rated frequency (Hz) | 118 |
Stator outer diameter (mm) | 260 |
Stator bore (mm) | 170 |
Rotor bore (mm) | 60 |
Number of conductors per slot | 16 |
End ring thickness (mm) | 13.5 |
Average outer diameter of end ring (mm) | 134 |
Rotor total groove height (mm) | 25 |
TABLE 1
TABLE 2 Motor Performance when Motor is run in full load with a Ring-less rotor
TABLE 2
When the motor runs by adopting the traditional cage type rotor, the conducting bar is electrically dense B =2.89A/mm 2 End ring electric seal J R =2.21A/mm 2 And the motor is in accordance with the designed electric density range of the motor. When the corresponding motor rotor type is an intermediate ring rotor, the designed intermediate ring electric density range J IR =(2.21-2.89)A/mm 2 。
And step two, determining a middle ring current amplitude relational expression according to the space distribution characteristics of the rotor current, and obtaining a rotor equivalent resistance expression. The amplitude of the intermediate ring current is estimated from the known bar currents of the rotor machine without the intermediate ring, and the range of the intermediate ring cross-sectional area is obtained.
As shown in the schematic structural diagram of the intermediate ring rotor winding in FIG. 1, the staggered distances of the upper and lower rotor bars are b st1 And b st2 Corresponding electrical angles are respectively beta 1 =pb st1 R and beta 2 =pb st2 R, wherein: p is the number of pole pairs of the motor, R is the radius of the rotor, Z 2 The number of rotor slots. The corresponding electrical angle of the rotor pitch is p2 pi/Z 2 It is obvious that the electrical angle relation α ═ β is satisfied 1 +β 2 。
As shown in the impedance network diagram of the intermediate ring rotor winding in fig. 2, if the stagger distances of the conducting bars are not equal, b is st1 ≠b st2 Through an odd number of intermediate ring currents I IR(2n-1) And even-order intermediate loop current I IR(2n) Phasor operation, upper bar current phasor I BU And lower side conducting bar current phasor I BL Respectively expressed as:
upper side end ring current phasor is I RU The lower side end ring current phasor is I RL The current phasor of the conducting bar can be corresponded bySide end loop current phasor representation:
and subtracting the phasor of the upper and lower conducting bar currents on the two adjacent sides to obtain an expression of the intermediate loop current for odd times, and obtaining the expression of the intermediate loop current for even times by the same method.
The intermediate ring rotor is assumed to be a symmetrical rotor, i.e. the rotor cores have equal axial length l 1 =l 2 L, the sectional areas of the upper and lower conducting bars and the end rings are equal, the amplitudes of the end ring currents at the two ends are equal to I RU =I RL =I R The amplitude of the conducting bar current is equal to I BU =I BL =I B Since the bar current phasor is equal to the difference in the adjacent end ring current phasors on the corresponding side, the magnitude of the end ring current can be expressed as:
according to the phasor relation of the currents of the adjacent end rings, the odd-order and even-order current amplitude relations of the intermediate ring are respectively as follows:
the equivalent rotor resistance expression of the intermediate ring rotor is as follows:
suppose at this time that the intermediate ring rotor is offset by a distance b st1 =b st1 =t 2 2, so corresponding electrical angle β 1 =β 2 The even and odd intermediate ring currents are equal in magnitude of about 155.78A at α/2, and the intermediate ring cross-sectional area ranges from (53.9-70.5) mm 2 。
And step three, taking a plurality of numerical points within the radial width range, respectively determining the respective axial height range according to the sectional area range, calculating the resistance value of the equivalent rotor resistor, and selecting the intermediate ring parameter when the equivalent rotor resistor is the minimum.
The radial width range of the middle ring is about 19-31mm, a plurality of numerical points are taken at intervals of 2mm, the axial height range of each radial width is obtained according to the sectional area range of the middle ring, and the value of the equivalent rotor resistance under the corresponding condition is obtained.
Table 3 is a table of equivalent rotor resistance values for the intermediate ring rotor winding, where the radial width and axial height of the intermediate ring are in mm and the resistance is in 10 -5 Ω。
TABLE 3
The minimum value of the equivalent resistance value of the rotor is found to be 7.45 multiplied by 10 through calculation -5 Ω and there are many intermediate ring design combinations that can reach this minimum. Obviously, the smaller the electrical density of the intermediate ring, i.e. the larger the current flow cross-sectional area at this time, the smaller the equivalent resistance value of the rotor. According to the motor application and the actual processing technology, the design parameters of the intermediate ring are reasonably selected, and if the inner diameter of the rotor is smaller, the radial width is 19mm and the axial height is 3.7mm, so as to avoid the situation that the rotor is not large in diameterThe rotor core is deformed by lamination; if the core length is small, a radial width of 31mm and an axial height of 2.2mm may be selected to avoid a reduction in output torque.
As shown in fig. 4-5, the intermediate ring designed by the method is applied to the rotor winding and the rotor core.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.
Claims (2)
1. A rotor intermediate ring structure is characterized by comprising an intermediate ring body, wherein the axial height of the intermediate ring body is as follows:in the formulaIs the end ring axial height;
2. The method of designing a rotor intermediate ring structure of claim 1, comprising the steps of:
step one, calculating the conducting bar electric density when the corresponding motor adopts a single-chute rotor to operateAnd end ring electric sealDetermining the electrical density range of the intermediate ring as;
Determining a current amplitude relation formula of the intermediate ring according to the space distribution characteristics of the rotor current, wherein the current amplitude relation formulas of the intermediate ring for odd times and even times are respectively as follows:
in the formula:the staggered distance of the upper rotor conducting bars is adopted,the staggered distance of the lower rotor conducting bars,to be the magnitude of the end-ring current,Rwhich is the radius of the rotor, is,pthe number of pole pairs of the motor is;
the magnitude of the end-ring current is:
in the formula:αthe pitch of the rotor corresponds to the electrical angle and,is the amplitude of the conducting bar current;
determining the range of the sectional area of the intermediate ring according to the electric density range of the intermediate ring in the step one and the current amplitude of the intermediate ring determined in the step two;
determining a rotor equivalent resistance expression:
in the formula:is the resistivity of the rotor windings and,the length of the conducting bar is equivalent to the length of the conducting bar,the average diameters of the end rings and the intermediate rings respectively,andrespectively the sectional areas of the conducting bar, the end ring and the middle ring,in order to obtain the pitch of the rotor teeth,the number of rotor slots;
taking a plurality of numerical points within the radial width range of the intermediate ring body, respectively determining the axial height range of each intermediate ring body according to the sectional area of the intermediate ring, calculating the resistance value of the rotor equivalent resistance, and selecting the intermediate ring parameter when the rotor equivalent resistance is minimum;
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