Design calculation method for air-air cooler of electric machine

Abstract

The application discloses a design calculation method of an air-to-air cooler for a motor, and comprises the following steps: step one, preliminarily determining key parameters of the motor and preliminarily determining key parameters of the cooler according to a heat exchange capacity P of the cooler; step two, checking whether an air temperature difference △T1 of an air inlet and an air outlet of an outer air path of the cooler meets control requirements, and checking a pressure loss F3 of the outer air path; step three, checking whether an air temperature difference △T2 of an air inlet and an air outlet of an inner air path of the cooler meets control requirements, and checking a pressure loss F4 of the inner air path; and step four, repeatedly adjusting the key parameters in step one until the checking in steps two and three is completed, and checking whether the heat exchange capacity of the cooler meets use requirements. The application provides a standard quantitative calculation analysis method for the design of the air-to-air cooler for the motor, and realizes fine design.

Description

TECHNICAL FIELD

[0001] The application relates to a design calculation method of an air-to-air cooler for a motor, relates to ventilation and heat dissipation of a motor and design calculation of an air-to-air cooler for the motor, and belongs to the technical field of motors. BACKGROUND

[0002] An air-to-air cooling motor with an IC611 structure is shown in a schematic diagram of a ventilation and heat dissipation structure of the motor. Figure 1 The heat P generated by internal components such as a stator and a rotor of the motor is brought into an air-to-air cooler (also referred to as a heat exchanger) at the upper part of the motor through circulation of air in the motor, is exchanged to air flowing in the air-to-air cooler through heat dissipation pipes in the air-to-air cooler, is transmitted and diffused to an atmospheric environment outside the motor through an external air path of the motor, so that heat dissipation balance of the motor in a certain temperature range is maintained, continuous operation of the motor is maintained, and the motor is prevented from being burned due to excessively high temperature. Driving force required by the internal and external air paths of the motor is provided by a fan provided on a rotating shaft of the motor. The heat transmission process is commonly referred to as ventilation and heat dissipation of the motor. When the ventilation and heat dissipation structure of the motor is determined, the air resistance of the internal circulation air path of the motor should be controlled within a reasonable range, so that sufficient circulation air volume of the internal circulation air path of the motor is ensured, and the heat of the motor stator and rotor can be transmitted to the air-to-air cooler.

[0003] A schematic diagram of a structure of the air-to-air cooler is shown in the accompanying Figure 2 The air-to-air cooler functions to transmit the heat of the air in the motor to the air outside the motor, and to realize heat transmission between the inside and outside of the motor. Design of the air-to-air cooler of the motor mainly includes determining the required number and arrangement mode of the cooling pipes according to the heat exchange capacity P of the cooler, the determined boundary conditions such as geometric dimensions, and simultaneously determining the geometric dimensions of the internal fan and the external fan of the motor.

[0004] At present, there is no standard calculation and analysis method for the design of the air-to-air cooler for the motor. The design method mainly adopts an analogy design method, that is, a reference cooler with a similar structure is found, the number of the cooling pipes is increased or reduced according to the increase or reduction of the heat exchange capacity P of the newly designed cooler, the relevant dimensions of the fan are adjusted according to the past experience, and the design work is completed. The design method of analogy and experience cannot perform quantitative design calculation and analysis of the air-to-air cooler, and the design margin of the cooler is excessively large, and the manufacturing cost is high. Because the design of the cooler has no corresponding calculation and analysis, the design is very subjective and random. The designed cooler cannot be matched with the ventilation and heat dissipation requirement of the motor, and the normal temperature of the motor is increased, and the motor is unqualified. SUMMARY

[0005] The application aims to solve the technical problem that the design of the existing air-to-air cooler for the motor has no standard calculation and analysis method, and the designed cooler cannot be matched with the ventilation and heat dissipation requirement of the motor, and the normal temperature of the motor is increased and the motor is unqualified.

[0006] To solve the above-mentioned technical problems, the technical solution of this application is to provide a design calculation method for an air cooler for an electric motor, including the following steps:

[0007] Step 1: Based on the heat exchange capacity P of the cooler design, preliminarily determine the key parameters of the motor and the cooler.

[0008] Step 2: Based on the preliminarily determined key parameters of the motor and cooler, calculate whether the inlet and outlet air temperature difference ΔT1 of the cooler's external air duct meets the control requirements. ΔT1 needs to be controlled between 10 and 20K. Calculate the pressure loss F3 of the external air duct. The pressure loss F3 of the external air duct needs to be less than the maximum pressure P that the motor's external fan can generate. 外 ;

[0009] Step 3: Based on the preliminarily determined key geometric dimensions of the motor, calculate whether the inlet and outlet air temperature difference ΔT2 in the cooler's internal airflow meets the control requirements. ΔT2 needs to be controlled between 15 and 30K. Calculate the internal airflow pressure loss F4. The internal airflow pressure loss F4 needs to be less than 0.5P of the maximum pressure that the motor's internal fan can generate. 内 ;

[0010] Step 4: Repeatedly adjust the key parameters in Step 1 until Step 2 and Step 3 are completed. Then, calculate whether the heat exchange capacity of the cooler meets the usage requirements. The actual heat exchange capacity P1 of the cooler should be greater than the preset heat exchange capacity P.

[0011] Specifically, the key parameters of the motor include: aerodynamic efficiency η, and the inner diameter d of the external fan. 外 ,

[0012] The outer diameter D of the external fan 外 Width H of the external fan 外 The inner diameter d of the internal fan 内 The outer diameter D of the internal fan 内 Width H of the internal fan 内 Air density ρ, motor speed N;

[0013] Maximum wind pressure P of external fan 外 =0.0027ηρN 2 (D 外 2 -d 外 2 );

[0014] Maximum air pressure P of internal fan 内 =0.0027ηρN 2 (D 内 2 -d 内 2 );

[0015] Fan flow coefficient K;

[0016] Outer fan maximum flow Q 外 = 0.148KND 外 2 H 外 ;

[0017] Inner fan maximum flow Q 内 = 0.148KND 内 2 H 内 ;

[0018] The cooler key parameters include: cooler design heat exchange capacity P, length L of cooling pipe, inner diameter D1 of cooling pipe, outer diameter D2 of cooling pipe, row number E of cooling pipe, column number F of cooling pipe, row spacing a, column spacing b, total number N of cooling pipes = EF, air dynamic viscosity μ in pipe, friction resistance coefficient λ, pipe mouth air inlet end wind resistance coefficient ζ;

[0019] Outer air inlet area S1 = 0.785 (D1 2 )N;

[0020] Cooling pipe inner air speed V1 = 0.5Q 外 / S1;

[0021] Pipe inner fluid Reynolds number R e = ρV1D1 / μ;

[0022] Cooling pipe inner pressure loss F1 = 0.5λρLV1 2 / D1;

[0023] Pipe mouth air inlet end pressure loss F2 = 0.5ζρV1 2 ;

[0024] Total pressure loss F3 of outer air path = F1+F2; check F3≤P 外 ;

[0025] Outer air path air inlet temperature T1, air constant volume specific heat C1; air temperature rise △T1 of outer air path = P / (0.6Q 外 C1), △T1 needs to be controlled between 10-20K;

[0026] Inner air path air inlet area S2 = 0.5LE(a-D2);

[0027] Inner air path pipe outer air speed V2 = 0.4Q 内 / S2; air constant volume specific heat C2;

[0028] Inner air path air inlet and outlet temperature difference △T2 = P / (0.5Q 内C2); △T2 needs to be controlled between 15-30K;

[0029] Pipe outside fluid Reynolds number R e = ρV2D2 / μ; Correction factor of resistance coefficient △ζ, resistance coefficient ζ1=3.587R e - 0.27 F+△ζ;

[0030] The air pressure drop F4 of the inner air path = 2·0.5·ζ1·ρV2 2 , needs to meet F4≤0.5P 内 ;

[0031] Motor temperature rise estimation △T3=△T1+5+△T2+10, needs to meet △T3<80;

[0032] Cooling pipe outer surface area S3=πD2LN; Cooling pipe inner surface area S4=πD1LN;

[0033] Cooling pipe wall thickness δ; Cooling pipe thermal conductivity λ1;

[0034] Pipe inner surface heat dissipation coefficient α1=0.001(30V1 0.5 -20);

[0035] Pipe outer surface heat dissipation coefficient α2=0.001(30V2 0.5 -20);

[0036] Cooling device comprehensive heat dissipation coefficient K=1 / (1 / α1+1 / α2+δ / λ1);

[0037] The average logarithmic temperature difference between the inner and outer air paths △T=(△T2-△T1) / ln(1+0.05(△T2-△T1));

[0038] The actual heat exchange capacity of the cooler P1=S3·K·△T, needs to meet P1≥P.

[0039] The application provides a standard quantitative calculation analysis method for the design of air-to-air coolers for motors, and realizes fine design. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 It is a schematic diagram of motor ventilation and heat dissipation structure, wherein T1 is the inlet air temperature of the outer air path, T2 is the outlet air temperature of the outer air path, T3 is the inlet air temperature of the inner air path, T4 is the outlet air temperature of the inner air path, Q1 is the air volume of the outer air path, Q2 is the air volume of the inner air path, H1 is the air pressure of the outer air path, H2 is the air pressure of the inner air path, 1 is the motor stator, 2 is the air-to-air cooler, 3 is the motor rotor, 4 is the inner fan, and 5 is the outer fan;

[0041] Figure 2Structure diagram of air-to-air cooler;

[0042] Figure 3 Tube arrangement diagram of cooler, wherein E is the number of rows of cooling tubes, F is the number of columns of cooling tubes, a is the row spacing, and b is the column spacing;

[0043] Figure 4 The principle and flow chart of the calculation method provided in the embodiment. DETAILED DESCRIPTION

[0044] In order to make the application more obvious and easy to understand, the preferred embodiment is described in detail below with the help of the accompanying drawings.

[0045] EMBODIMENT

[0046] The purpose of the embodiment is to provide a design calculation method for air-to-air coolers for electric machines. Under the known conditions of the operating speed of the electric machine, the design heat exchange capacity P of the cooler, and the related geometric dimensions, the design calculation analysis of the air-to-air cooler for the electric machine is carried out, and the following calculation results are output: 1. checking whether the heat exchange capacity P of the cooler meets the design requirements and has a certain design margin; 2. determining the number and arrangement of the heat dissipation tubes required by the air-to-air cooler; and 3. checking whether the geometric dimensions of the fan inside the electric machine and the fan outside the electric machine meet the use requirements.

[0047] The embodiment analyzes the above requirements Figure 1 The process of ventilation and heat dissipation of the electric machine and the internal mutual logical relationship thereof are shown, the key control parameters are proposed in combination with the previous practical experience, the classical theories and calculation formulas of heat transfer, fluid mechanics, and centrifugal fan design are comprehensively used, the design calculation analysis process of the air-to-air cooler for the electric machine is prepared in the form of an electronic form, the value range of the related parameters in the calculation process is set in combination with the test data of the electric machine, and is continuously revised and improved. Through verification in recent years, the calculation method meets the design calculation requirements of the air-to-air cooler in the precision range of the electric machine engineering design calculation, achieves the quantitative analysis and calculation of the air-to-air cooler, realizes the purpose of fine design, and improves the design capability of the air-to-air cooler.

[0048] The principle and flow of the calculation method of the air-to-air cooler for the electric machine are shown in the attached Figure 4 ; The calculation method is described as follows:

[0049] S1, according to the design heat exchange capacity P of the cooler, referring to the existing design data of the same type, the key parameters such as the inner diameter, the outer diameter, and the width of the inner fan and the outer fan of the electric machine are preliminarily determined, and the key parameters of the cooler are preliminarily determined;

[0050] S2, according to the preliminary determination of the motor key parameters and cooler key parameters, accounting for the cooler outside air temperature rise △T1 whether to meet the control requirements, according to the experience value △T1 need to control between 10~20K; while accounting for the total pressure loss F3 of the outer air path, the outer air path pressure loss includes two parts, one part is the air into the cooling pipe when the nozzle pressure loss, the other part is the air flow in the cooling pipe generated by the pressure loss, the outer air path pressure loss F3 need to be less than the highest wind pressure P generated by the motor fan 外 ; otherwise, the cooling pipe has no wind, can not meet the requirements of heat transfer;

[0051] S3, according to the preliminary determination of the motor key parameters and cooler key parameters, accounting for the cooler inside air temperature difference △T2 whether to meet the control requirements, according to the experience value △T2 need to control between 15~30K; while accounting for the inner air path pressure loss F4, the inner air path pressure loss F4 need to be less than the highest pressure 0.5P generated by the motor fan 内 , otherwise, the motor internal air circulation can not be flow, can not be transmitted to the internal heat of the motor to the inside of the cooler;

[0052] S4, repeated adjustment of the key parameters in step one until step two, step three accounting for the completion, also need to account for the heat transfer capacity of the cooler whether to meet the use requirements, the actual heat transfer capacity of the cooler P1 is greater than the preset heat transfer capacity P, and has a certain design margin.

[0053] It should be noted that the application of this calculation method is limited to the professional range, only in the design of motor air cooling cooler, and need to have certain motor professional knowledge personnel use. In the use process, the size of the inner and outer fan and the number of cooling pipe need to be taken into account, sometimes need to be adjusted repeatedly to meet the design requirements.

[0054] In order to verify whether the calculation method meets the design requirements, select different types of multiple motor, motor test, the internal and external air temperature of the motor T1, T2, T3, T4 and internal and external air flow Q1, Q2, the comparison results show that the measured value and the calculated value are basically consistent, the error is within 5%. The following YKK series motor air-cooled cooler design calculation analysis process as an example, the detailed process is shown in the following table:

[0055] YKK series motor air-cooled cooler design calculation analysis

[0056]

[0057]

[0058]

[0059]

[0060] In possible embodiments, if the outer fan of the motor is cancelled and an independent blower is used, i.e. the ventilation cooling form of the motor is IC616, the air volume and air pressure directly input into the outer air path, and the method can also be used after modification; if the inner and outer fans of the motor are cancelled and an independent blower is used, i.e. the ventilation cooling form of the motor is IC666, the air volume and air pressure directly input into the inner and outer air paths, and the method can also be used after modification.

Claims

1. A design calculation method for an air cooler for an electric motor, characterized in that, Includes the following steps: Step 1: Based on the heat exchange capacity P of the cooler design, preliminarily determine the key parameters of the motor and the cooler. Step two, according to the preliminary determined motor key parameters and cooler key parameters, calculate whether the inlet and outlet air temperature difference of the cooler outer air path ΔT1 meets the control requirements, ΔT1 needs to be controlled between 10-20K; calculate the outer air path pressure loss F3, the outer air path pressure loss F3 needs to be less than the highest pressure P that the motor outer fan can produce 外 ; Step three, according to the preliminary determined key geometry size of the motor, calculate whether the temperature difference △T2 of the inlet and outlet air of the cooler meets the control requirements, △T2 needs to be controlled between 15-30K; calculate the pressure loss F4 of the inner air path, the pressure loss F4 of the inner air path needs to be less than the highest pressure 0.5P that the motor inner fan can produce 内 ; Step 4: Repeatedly adjust the key parameters in Step 1 until Step 2 and Step 3 are completed. Then, calculate whether the heat exchange capacity of the cooler meets the usage requirements. The actual heat exchange capacity P1 of the cooler should be greater than the preset heat exchange capacity P. The key parameters of the electric fan include: aerodynamic efficiency η, inner diameter d of the outer fan 外 , Outer diameter D of outer fan 外 Width H of outer fan 外 Inner diameter d of inner fan 内 Outer diameter D of inner fan 内 Width H of inner fan 内 Air density p, motor rotation speed N Pmax: maximum wind pressure of the outer fan 外 = 0.0027ηρN 2 (D 外 2 -d 外 2 ); Maximum air pressure P of internal fan 内 =0.0027ηρN 2 (D 内 2 -d 内 2 ); Fan flow coefficient K; External fan maximum flow rate Q 外 =0.148KND 外 2 H 外 ; Maximum airflow of internal fan Q 内 =0.148KND 内 2 H 内 ; The key parameters of the cooler include: the design heat exchange capacity P of the cooler, the length L of the cooling tube, the inner diameter D1 of the cooling tube, the outer diameter D2 of the cooling tube, the number of rows E of the cooling tube, the number of columns F of the cooling tube, the row spacing a, the column spacing b, the total number of cooling tubes N = EF, the dynamic viscosity of the air inside the tube μ, the friction resistance coefficient λ, and the air resistance coefficient ζ at the air inlet of the tube. The air inlet area of ​​the external air duct is S1 = 0.785 (D1) 2 N; The air velocity inside the cooling pipe is V1 = 0.5Q. 外 / S1; Reynolds number R of fluid inside the pipe e =ρV1D1 / μ; The pressure loss inside the cooling pipe is F1 = 0.5λρLV1 2 / D1; Pressure loss at the air inlet of the pipe: F2 = 0.5ζρV1 2 ; The total pressure loss of the external ventilation path is F3 = F1 + F2; check that F3 ≤ P. 外 ; The inlet air temperature T1 of the external air duct and the specific heat of the air at constant volume C1; the air temperature rise ΔT1 of the external air duct = P / (0.6Q) 外 C1), △T1 needs to be controlled between 10 and 20K; The air intake area of ​​the internal air duct is S2 = 0.5LE(a-D2); The external wind speed in the internal air duct is V2 = 0.4Q. 内 / S2; Specific heat at constant volume of air C2; Temperature difference between inlet and outlet air in the internal air duct ΔT2=P / (0.5Q) 内 C2); △T2 needs to be controlled between 15 and 30K; Reynolds number R of the fluid outside the pipe e =ρV²D² / μ; Correction factor for drag coefficient Δζ, drag coefficient ζ₁ = 3.587R e -0.27 F+△ζ; The internal airflow pressure drop F4 = 2·0.5·ζ1·ρV2 2 The condition F4 ≤ 0.5P must be met. 内 ; The estimated temperature rise of the motor is ΔT3 = ΔT1 + 5 + ΔT2 + 10, which must satisfy ΔT3 < 80. The outer surface area of ​​the cooling pipe is S3 = πD2LN; the inner surface area of ​​the cooling pipe is S4 = πD1LN. Cooling pipe wall thickness δ; cooling pipe thermal conductivity λ1; The heat dissipation coefficient of the inner surface of the tube is α1 = 0.001 (30V1). 0.5 -20); The heat dissipation coefficient of the outer surface of the tube is α2 = 0.001 (30V2). 0.5 -20); The overall heat dissipation coefficient of the cooler is K = 1 / (1 / α1 + 1 / α2 + δ / λ1); The average logarithmic temperature difference between the internal and external air ducts is ΔT = (ΔT2 - ΔT1) / ln(1 + 0.05(ΔT2 - ΔT1)). The actual heat exchange capacity of the cooler is P1 = S3·K·△T, which must satisfy P1≥P.

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