阅读说明：本技术 一种转子中间环结构及其设计方法 (Rotor intermediate ring structure and design method thereof ) 是由 鲍晓华 徐威 许东滢 汤亦追 燕靖文 朱然 于 2019-11-14 设计创作，主要内容包括：本发明公开了一种转子中间环结构及其设计方法，一种转子中间环结构，包括中间环本体，中间环本体的轴向高度为：l<Sub>IR</Sub>∈(0,l<Sub>R</Sub>/3]，式中：l<Sub>R</Sub>是端环轴向高度。中间环本体的径向宽度为：b<Sub>IR</Sub>∈[3b<Sub>t2</Sub>/4,(D<Sub>2</Sub>?D<Sub>0</Sub>+6b<Sub>t2</Sub>)/8]；一种转子中间环结构的设计方法，包括以下步骤：确定中间环电密范围为J<Sub>IR</Sub>＝(J<Sub>R</Sub>?J<Sub>B</Sub>)；确定中间环电流幅值关系式，并得到转子等效电阻表达式；由已知的无中间环转子电机的导条电流估计中间环电流幅值，并得到中间环截面积的范围；选择最小等效电阻时的中间环参数。本发明在考虑转子铁心实际加工情况的基础上，确保中间环转子绕组各部分散热均匀，尽量减小转子绕组损耗。(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 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](ii) a A design method of a rotor intermediate ring structure comprises the following steps: determining the electric density range of the intermediate ring to be 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 dissipate heat uniformly on the basis of considering the actual processing condition of the rotor coreAnd the loss of the rotor winding is reduced as much as possible.)

1. A rotor intermediate ring structure comprising an intermediate ring body having an axial height of: l_IR∈(0,l_R/3]In the formula I_RIs the end ring axial height;

the radial width of the intermediate ring body is: b_IR∈[3b_t2/4,(D₂-D₀+6b_t2)/8]In the formula b_t2For rotor slot height, D₂Is the diameter of the outer circle of the rotor D₀Is the diameter of the inner circle of the rotor.

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 J when the corresponding motor adopts a single-chute rotor to operate_BAnd end ring electrical seal J_RDetermining the electric density range of the intermediate ring to be J_IR＝(J_R-J_B)；

Determining a relation of intermediate ring current amplitude values according to the space distribution characteristics of the rotor current, 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;

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.

3. The method for designing the intermediate ring structure of the rotor as claimed in claim 2, wherein the current amplitude relations of the odd number and the even number of the intermediate ring in the second step are respectivelyIn the formula β₁＝pb_st1/R、β₂＝pb_st2/R，b_st1For staggered distances of upper rotor conducting bars, b_st2For staggered distance of the lower rotor conducting bars, I_RThe amplitude of the end-ring current, R the rotor radius, and p the number of pole pairs of the motor.

4. A method of designing a rotor intermediate ring structure according to claim 3, characterized in that the amplitude of the end ring current isWherein α is the corresponding electrical angle of rotor pitch and α ═ p2 π/Z₂，I_BThe amplitude of the bar current.

5. The method for designing the intermediate ring structure of the rotor according to claim 2, wherein the equivalent resistance of the rotor in the second step is as follows:

6. The method for designing the intermediate ring structure of the rotor according to claim 2, wherein the sectional area of the intermediate ring in the second step is: a. the_IR＝l_IR×b_IRIn the formula: l_IRIs the axial height of the intermediate ring body, b_IRThe radial width of the intermediate ring body.

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 when the motor structure is designed. For a cage type cast aluminum rotor of a common medium and small-sized motor, a conducting bar electric density J is usually taken_B＝(2.0-4.5)A/mm²End 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 distort the magnetic field of the motor, and cause the deterioration of the performance of the motor in various aspects, such as the fluctuation of the output torque of the motor, the generation of additional electromagnetic force 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:

the rotor intermediate ring structure comprises an intermediate ring body, and an axial direction of the intermediate ring bodyThe height is as follows: l_IR∈(0,l_R/3]In the formula: l_RIs the end ring axial height. The radial width of the intermediate ring body is: b_IR∈[3b_t2/4,(D₂-D₀+6b_t2)/8]In the formula: b_t2Height of rotor slots, D₂Is the diameter of the outer circle of the rotor, D₀Is 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_BAnd end ring electrical seal J_RDetermining the electric density range of the intermediate ring to be 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_st1And b_st2Corresponding to an electrical angle of β respectively₁＝pb_st1R and β₂＝pb_st2R, wherein: p is the number of pole pairs of the motor, R is the radius of the rotor, Z₂The number of the rotor slots, the corresponding electrical angle of the rotor pitch is α ═ p2 π/Z₂It is clear that the electrical angle relation α - β is satisfied₁+β₂。

If the stagger distances of the conducting bars are not equal, the conducting bars are b_st1≠b_st2Through 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_BUAnd lower conductor current phasor I_BLRespectively expressed as:

upper side end ring current phasor is I_RUThe lower side end ring current phasor is I_RLThe bar current phasor can 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 l₁＝l₂L, 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_RThe amplitude of the conducting bar current is equal to I_BU＝I_BL＝I_BSince 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 rotor₂The 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_BIs a conducting bar resistance, Z₂Is the number of rotor slots, R_RIs the end ring segment resistance between adjacent conducting bars, the middle ring is staggered by a distance b_st1And b_st2The corresponding intermediate ring resistances are respectively R_IR1And R_IR2If the middle ring resistance in the range of the rotor pitch is R_IRObviously satisfies the intermediate ring resistance relation R_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_wIs the resistivity of the rotor winding, /)_BFor equivalent length of the conducting strip, D_R，D_IRAverage diameters of end rings and intermediate rings, A_B，A_RAnd A_IRThe cross-sectional areas of the conducting bars, the end rings and the intermediate ring are respectively, wherein the cross-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，t₂Is the pitch of the rotor, Z₂Is the number of rotor slots, b_st1And b_st2The upper rotor conducting bar and the lower rotor conducting bar are staggered.

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 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 conforms to the design principle of the motor;

2) the invention ensures the proper current density of the intermediate ring and the uniform heat dissipation distribution of the rotor winding;

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 the 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 of uniform heat dissipation of all parts of the rotor winding, the equivalent resistance of the rotor is reduced, so that the winding loss of the motor in operation 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 of 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_RIs the end ring axial height. The radial width of the intermediate ring body is: b_IR∈[3b_t2/4,(D₂-D₀+6b_t2)/8]In the formula:b_t2height of rotor slots, D₂Is the diameter of the outer circle of the rotor, D₀Is 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 ringless rotor

TABLE 2

When the motor runs by adopting the traditional cage type rotor, the conducting bar is electrically dense_B＝2.89A/mm²End ring electric seal J_R＝2.21A/mm²And 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/mm²。

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_st1And b_st2Corresponding to an electrical angle of β respectively₁＝pb_st1R and β₂＝pb_st2R, wherein: p is the number of pole pairs of the motor, R is the radius of the rotor, Z₂The number of the rotor slots, the corresponding electrical angle of the rotor pitch is α ═ p2 π/Z₂It is clear that the electrical angle relation α - β is satisfied₁+β₂。

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_st2Go through the chessSeveral times of intermediate ring current I_IR(2n-1)And even-order intermediate loop current I_IR(2n)Phasor operation, upper bar current phasor I_BUAnd lower conductor current phasor I_BLRespectively expressed as:

upper side end ring current phasor is I_RUThe lower side end ring current phasor is I_RLThe bar current phasor can 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 l₁＝l₂L, 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_RThe amplitude of the conducting bar current is equal to I_BU＝I_BL＝I_BSince 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 now that the intermediate ring rotor is offset by a distance b_st1＝b_st1＝t₂2, so corresponding electrical angle β₁＝β₂α/2, equal amplitude of current in odd and even intermediate ring of 155.78A, cross-sectional area of intermediate ring of (53.9-70.5) mm²。

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^-5Ω。

TABLE 3

The minimum value of the equivalent resistance value of the rotor is found to be 7.45 multiplied by 10 through calculation^-5Ω 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 application of the motor 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 that the rotor core is prevented from being laminated and deformed; 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.