CN111222279A - Design method of high-power-density motor cooling system and motor designed by method - Google Patents
Design method of high-power-density motor cooling system and motor designed by method Download PDFInfo
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- 238000001816 cooling Methods 0.000 title claims abstract description 28
- 238000000034 method Methods 0.000 title claims abstract description 24
- 238000013461 design Methods 0.000 title claims abstract description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 194
- 239000000110 cooling liquid Substances 0.000 claims abstract description 74
- 239000002826 coolant Substances 0.000 claims abstract description 21
- 238000004804 winding Methods 0.000 claims abstract description 15
- 230000008859 change Effects 0.000 claims description 3
- 230000004907 flux Effects 0.000 claims description 3
- 230000008569 process Effects 0.000 claims description 3
- 230000017525 heat dissipation Effects 0.000 abstract description 10
- 239000007788 liquid Substances 0.000 abstract description 5
- 230000004323 axial length Effects 0.000 description 7
- 238000009826 distribution Methods 0.000 description 5
- BGPVFRJUHWVFKM-UHFFFAOYSA-N N1=C2C=CC=CC2=[N+]([O-])C1(CC1)CCC21N=C1C=CC=CC1=[N+]2[O-] Chemical compound N1=C2C=CC=CC2=[N+]([O-])C1(CC1)CCC21N=C1C=CC=CC1=[N+]2[O-] BGPVFRJUHWVFKM-UHFFFAOYSA-N 0.000 description 4
- 230000003247 decreasing effect Effects 0.000 description 4
- 230000006872 improvement Effects 0.000 description 4
- 238000011161 development Methods 0.000 description 2
- 230000018109 developmental process Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 229910000976 Electrical steel Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000005347 demagnetization Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000004382 potting Methods 0.000 description 1
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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
- H02K15/14—Casings; Enclosures; Supports
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K5/00—Casings; Enclosures; Supports
- H02K5/04—Casings or enclosures characterised by the shape, form or construction thereof
- H02K5/20—Casings or enclosures characterised by the shape, form or construction thereof with channels or ducts for flow of cooling medium
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K9/00—Arrangements for cooling or ventilating
- H02K9/19—Arrangements for cooling or ventilating for machines with closed casing and closed-circuit cooling using a liquid cooling medium, e.g. oil
Abstract
The invention relates to a design method of a high-power-density motor cooling system and a motor designed by the method. The motor comprises a rotor assembly, a stator assembly and a cooling system. The rotor assembly includes a rotor yoke and a permanent magnet. The stator assembly includes a stator yoke, a stator housing, stator teeth, and stator windings. The cooling system is integrated into the stator assembly. The cooling system comprises a water inlet, a water outlet and a cooling liquid flow passage, wherein the cooling liquid flow passage is arranged inside the stator shell. The heat that stator winding produced transmits to stator shell through the stator yoke, transmits to the coolant liquid by stator shell again, and the coolant liquid velocity of flow risees by water inlet to delivery port gradually among the cooling system, can effectual increase be close to the heat dissipation capacity of the coolant liquid of delivery port for motor stator's temperature field distributes evenly, has the significance to the radiating efficiency and the power density that improve the motor.
Description
Technical Field
The invention relates to the technical field of driving motors, in particular to a method for designing a cooling system of a high-power-density motor and a motor designed by the method.
Background
Under the international background that the investment is increased in the field of new energy in all countries of the world, the weight and the volume of the driving motor are reduced, and the power of the driving motor is more and more important, so the development of the high-power-density driving motor is highly emphasized by all countries. The development target of an electric drive system is clear in the key special item of the national new energy automobile in 2018 of the department of science and technology: the power density of the motor of the passenger vehicle reaches 4.0kW/kg, and the torque density of the motor of the commercial vehicle reaches 18 Nm/kg. Along with the increase of the power of the driving motor, the heating power inevitably rises due to the water, the heat productivity seriously hinders the improvement of the motor performance and limits the improvement of the motor power density, and a high-efficiency cooling system is firstly needed to improve the power density of the driving motor.
In a traditional motor cooling system, the equivalent diameter of a liquid cooling pipeline is a constant value. In the conventional parallel pipeline structure, the number of parallel pipelines is also a constant value. The temperature of the cooling liquid is gradually increased from the water inlet to the water outlet, the temperature difference between the wall surface and the cooling liquid is gradually reduced, the closer the cooling liquid is to the water outlet of the motor, the worse the heat dissipation condition of the motor is, the uneven temperature of the motor is, and the thermal performances of the motor are limited by the highest temperature point of the motor. The performance of the motor is reduced due to the local high temperature of the motor, the improvement of the power density is limited, meanwhile, the highest point temperature possibly exceeds the limit temperature of the winding to cause the winding to be burnt out, or the irreversible demagnetization of the permanent magnet is caused due to the overhigh local temperature, so that the motor is damaged. It follows that the realization of an electric machine with a uniform temperature distribution is the subject of considerable research.
Disclosure of Invention
The invention aims to provide a high-power density motor with uniform temperature distribution and a design method thereof, wherein the equivalent diameter of a liquid cooling pipeline is gradually changed from a water inlet to a water outlet, or the parallel number of the pipelines is decreased progressively from the water inlet to the water outlet, so that the flow speed of cooling liquid at the water outlet is increased, the convection heat exchange coefficient of a shell and the cooling liquid is increased, the heat dissipation capacity of a cooling system close to the water outlet is increased, the deterioration of the heat dissipation condition of the outlet caused by the temperature rise of the cooling liquid is compensated, and the temperature distribution of the motor is uniform; meanwhile, the winding and the permanent magnet at the water outlet are prevented from being damaged due to overhigh temperature, the function of protecting key parts of the motor is realized, and the motor is more reliable and efficient to operate.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method of designing a high power density motor cooling system, the method comprising the steps of:
(1) a cooling liquid flow channel is arranged in the motor stator shell, a water inlet and a water outlet which are communicated with the cooling liquid flow channel are arranged on the outer side of the motor stator shell, and the initial sizes of the water inlet and the water outlet are set; the coolant flow channel includes at least one shunt channel.
(2) Obtaining parameters of the motor under rated working condition, and calculating the winding resistance loss P of the motor under rated working condition by the following formulaCuAnd core loss PFe：
PCu＝mI2R (1)
PFe＝Pn+Pc(2)
Pn＝KnfBp x(3)
Pc＝Kcf2BP 2(4)
Wherein m is the phase number, I is the rated current, and R is the resistance value of the motor winding; pnFor hysteresis loss, pcIs the eddy current loss; b ispIs the magnetic flux density amplitude, KnAnd x is the hysteresis loss coefficient, KcF is the frequency of the alternating current.
Using the formula P ═ PFe+PCuDetermining the total of the electric machineLoss P.
(3) The temperature difference delta T of the cooling liquid between the water inlet and the water outlet is obtained by adopting the following formula:
wherein p is the total loss of the motor, Q is the flow rate of the cooling liquid, ρ is the density of the cooling liquid, and c is the specific heat capacity of the cooling liquid.
(4) The geometrical relationship between the water inlet and the water outlet is obtained by adopting the following formula:
wherein d is1Is the equivalent diameter of the water inlet, d2Is the equivalent diameter of the water outlet, N2The number of the shunt pipes connected with the water outlet in parallel is N1The number of the shunt pipes connected with the water inlet is in parallel connection, delta T-delta T is the temperature difference between the cooling liquid at the water outlet and the wall surface, and delta T is the temperature difference between the cooling liquid at the water inlet and the wall surface.
(5) And obtaining the optimal sizes of the water inlet and the water outlet through multiple iterations, so that the difference Y between the wall temperature of the water inlet and the wall temperature of the water outlet reaches the set precision Y.
Further, the step (5) of obtaining the optimal dimensions of the water inlet and the water outlet through multiple iterations to make the difference Y between the wall temperature of the water inlet and the wall temperature of the water outlet reach the set precision Y includes the specific processes:
(51) acquiring the wall surface temperature difference y between the water outlet and the water inlet;
(52) solving the relation between the equivalent diameters of the water inlet and the water outlet by adopting a formula (6), and modifying the size of the water outlet according to the relation between the equivalent diameters of the water inlet and the water outlet;
(53) acquiring the wall surface temperature difference y between the water inlet and the water outlet again;
(54) and judging whether Y is smaller than the set precision Y, if so, outputting the sizes of the water inlet and the water outlet by taking the sizes of the current water inlet and the current water outlet as the optimal sizes of the water inlet and the water outlet, and if not, returning to the step (52).
The invention also relates to a motor designed by adopting the design method, which comprises a stator assembly, a rotor assembly and a cooling system; the cooling system comprises a cooling liquid flow channel arranged in the stator shell and a water inlet and a water outlet which are respectively arranged on the outer side of the stator shell; the coolant flow channel comprises at least 1 flow dividing pipeline connected between the water inlet and the water outlet. The stator assembly comprises a stator yoke and a stator shell which are coaxially arranged from inside to outside in sequence, stator teeth arranged on the inner wall of the stator yoke and stator windings wound on the stator teeth; the rotor assembly comprises a rotor yoke and a plurality of permanent magnets adhered to the outer wall of the rotor yoke; gaps are arranged between the adjacent permanent magnets; the permanent magnet is in an arc shape matched with the rotor yoke; the permanent magnet adopts a block type structure and comprises a plurality of small permanent magnets which are bonded and connected.
Specifically, when the number of the flow dividing pipes is equal to 1, the cooling liquid flow passage comprises a spiral pipe which is connected between the water inlet and the water outlet and is coaxially arranged with the stator shell, and the central line of the spiral pipe is coincident with the axial central line of the stator shell; the equivalent diameter of the spiral pipeline is gradually reduced from the water inlet to the water outlet; the cross section of the spiral pipeline is rectangular.
When the number of the flow dividing pipelines is equal to 1, the cooling liquid flow channel comprises a plurality of longitudinal pipelines which are axially arranged along the stator shell, wherein the first longitudinal pipeline is communicated with the water inlet, and the last longitudinal pipeline is communicated with the water outlet; among other longitudinal pipelines, a connecting pipeline for communicating the two longitudinal pipelines is arranged between the two adjacent longitudinal pipelines, and the connecting pipelines are distributed in a staggered manner; the equivalent diameter of the cooling liquid flow channel is gradually reduced from the water inlet to the water outlet; the cross sections of the longitudinal pipelines and the connecting pipelines are rectangular.
When the number of the diversion pipelines is more than 1, the cooling liquid flow channel comprises a plurality of diversion pipelines I connected with the water inlet, a plurality of diversion pipelines II connected with the water outlet, a confluence pipeline I used for guiding the cooling liquid flowing in from the water inlet to the diversion pipelines I, a confluence pipeline II used for guiding the cooling liquid in the diversion pipelines I to the diversion pipelines II and a confluence pipeline III used for guiding the cooling liquid in the diversion pipelines II to the water outlet; the first shunt pipelines and the second shunt pipelines form a plurality of shunt pipelines, each shunt pipeline is arranged along the circumferential direction of the stator shell, and the shunt pipelines are uniformly distributed along the axial direction of the stator shell; the equivalent diameters of the same shunt pipeline are the same, and the equivalent diameters of the plurality of shunt pipelines gradually change along the axial direction of the stator shell. The first confluence pipeline, the second confluence pipeline and the third confluence pipeline are all distributed along the axial direction of the stator shell, and the equivalent diameters of the first confluence pipeline, the second confluence pipeline and the third confluence pipeline are the same. The cross sections of the first diversion pipeline, the second diversion pipeline, the first confluence pipeline, the second confluence pipeline and the third confluence pipeline are all rectangular.
Compared with the prior art, the invention has the beneficial effects that:
(1) the invention adopts the water channel structure with the equivalent diameter of the water channel decreased progressively or the number of the parallel water channels decreased progressively, so that the flow velocity of the cooling liquid closer to the water outlet is larger, the reduction of the heat dissipation capacity caused by the temperature rise of the cooling liquid is compensated, the temperature of the motor parts is uniform, the problem of local high temperature of the motor is solved, the highest temperature of the motor is reduced, the key parts of the motor are protected, and the power density of the motor can be further improved.
(2) The invention adopts a surface-mounted rotor structure, the magnetic leakage coefficient and the manufacturing cost are relatively small, and the permanent magnet adopts a block type structure, so that the generation of large eddy current in the permanent magnet can be effectively inhibited, the eddy current loss of the permanent magnet is reduced, the heat productivity of the permanent magnet is reduced, and the effects of improving the power density of the motor and protecting the permanent magnet are achieved.
Drawings
FIG. 1 is a flow chart of a design method of the present invention;
FIG. 2 is a schematic view of the structure of the motor of the present invention;
FIG. 3 is a schematic cross-sectional view of the motor of the present invention;
FIG. 4 is a schematic view of the structure of a permanent magnet according to the present invention;
FIG. 5 is a schematic structural view of a coolant flow path in the first embodiment;
FIG. 6 is a schematic structural view of a coolant flow path in the second embodiment;
FIG. 7 is a schematic structural view of a coolant flow path in the third embodiment;
FIG. 8 is a schematic view showing the flow direction of the cooling liquid in the cooling liquid flow path in the third embodiment;
wherein:
1. the water inlet comprises a water inlet body, 2, a water outlet body, 3, a stator shell, 4, a permanent magnet, 5, stator teeth, 6, a stator winding, 7, an air gap, 8, a rotor yoke, 9, a shunt pipeline, 10, a confluence pipeline, 11 and a stator yoke.
Detailed Description
The invention is further described below with reference to the accompanying drawings:
a method of designing a high power density motor cooling system as shown in fig. 1, the method comprising the steps of:
(1) a cooling liquid flow channel is arranged in the motor stator shell, a water inlet and a water outlet which are communicated with the cooling liquid flow channel are arranged on the outer side of the motor stator shell, and the initial sizes of the water inlet and the water outlet are set; the coolant flow channel includes at least one shunt channel.
(2) Obtaining parameters of the motor under rated working condition, and calculating the winding resistance loss P of the motor under rated working condition by the following formulaCuAnd core loss PFe：
PCu＝mI2R (1)
PFe＝Pn+Pc(2)
Pn＝KnfBp x(3)
Pc＝Kcf2BP 2(4)
Wherein m is the phase number, I is the rated current, and R is the resistance value of the motor winding; pnFor hysteresis loss, pcIs the eddy current loss; b ispIs the magnetic flux density amplitude, KnAnd x is the hysteresis loss coefficient, KcIs the eddy current loss coefficient, fIs the frequency of the alternating current.
Using the formula P ═ PFe+PCuAnd (6) obtaining the total loss P of the motor.
(3) The temperature difference delta T of the cooling liquid between the water inlet and the water outlet is obtained by adopting the following formula:
wherein p is the total loss of the motor, Q is the flow rate of the cooling liquid, ρ is the density of the cooling liquid, and c is the specific heat capacity of the cooling liquid.
(4) The geometrical relationship between the water inlet and the water outlet is obtained by adopting the following formula:
wherein d is1Is the equivalent diameter of the water inlet, d2Is the equivalent diameter of the water outlet, N2The number of the shunt pipes connected with the water outlet in parallel is N1The number of the shunt pipes connected with the water inlet is in parallel connection, delta T-delta T is the temperature difference between the cooling liquid at the water outlet and the wall surface, and delta T is the temperature difference between the cooling liquid at the water inlet and the wall surface.
(5) And obtaining the optimal sizes of the water inlet and the water outlet through multiple iterations, so that the difference Y between the wall temperature of the water inlet and the wall temperature of the water outlet reaches the set precision Y.
Further, the step (5) of obtaining the optimal dimensions of the water inlet and the water outlet through multiple iterations to make the difference Y between the wall temperature of the water inlet and the wall temperature of the water outlet reach the set precision Y includes the specific processes:
(51) acquiring the wall surface temperature difference y between the water outlet and the water inlet;
(52) solving the relation between the equivalent diameters of the water inlet and the water outlet by adopting a formula (6), and modifying the size of the water outlet according to the relation between the equivalent diameters of the water inlet and the water outlet;
(53) acquiring the wall surface temperature difference y between the water inlet and the water outlet again;
(54) and judging whether Y is smaller than the set precision Y, if so, outputting the sizes of the water inlet and the water outlet by taking the sizes of the current water inlet and the current water outlet as the optimal sizes of the water inlet and the water outlet, and if not, returning to the step (52).
The invention also relates to a motor designed by adopting the design method, which comprises a stator assembly, a rotor assembly and a cooling system. The cooling system comprises a cooling liquid flow channel arranged in the stator shell 3 and a water inlet 1 and a water outlet 2 which are respectively arranged on the outer side of the stator shell 3; the coolant flow channel comprises at least 1 flow dividing pipeline connected between a water inlet 1 and a water outlet 2. The stator assembly comprises a stator yoke 11 and a stator shell 3 which are coaxially arranged from inside to outside in sequence, stator teeth 5 arranged on the inner wall of the stator yoke 11 and a stator winding 6 wound on the stator teeth 5; the rotor assembly comprises a rotor yoke 8 and a plurality of permanent magnets 4 pasted on the outer wall of the rotor yoke 8; gaps are arranged between the adjacent permanent magnets 4; the permanent magnet 4 is in an arc shape matched with the rotor yoke 8; the permanent magnet 4 is of a block type structure and comprises a plurality of small permanent magnets which are bonded and connected. The inner surface of the stator teeth 5 is a circular surface and forms an annular air gap 7 together with the outer surface of the permanent magnet. The axial length of the stator housing 3 is greater than the axial length of the stator yoke 11. The axial length of the rotor yoke 8 is greater than the axial length of the stator yoke 11 and less than the axial length of the stator housing 3. The axial length of the permanent magnet 4 is equal to the axial length of the rotor yoke 8. The stator yoke 11 and the rotor yoke 8 are formed by laminating high-permeability and low-conductivity silicon steel sheets. The surfaces of the permanent magnet 4, the stator yoke 11 and the stator teeth 5 are subjected to insulation treatment, and a gap between the stator yoke 11 and the stator teeth 5 is filled with a potting material with a high heat conductivity coefficient.
The coolant flow channel according to the present invention will be described in three embodiments according to the number of the branch pipes and the shapes of the branch pipes. In three embodiments, each of the flow distribution conduits is rectangular in cross-section, the axial width of the flow distribution conduit is constant, and the equivalent diameter is varied by varying the radial height.
Example one
As shown in fig. 5, when the number of the branch pipes is equal to 1, the coolant flow passage includes a spiral pipe connected between the water inlet 1 and the water outlet 2 and disposed coaxially with the stator housing 3, and a center line of the spiral pipe coincides with an axial center line of the stator housing 3. The cross section of the spiral pipeline is rectangular. The equivalent diameter of the spiral pipeline is decreased progressively from the water inlet 1 to the water outlet 2, so that the problem of uneven axial temperature of the motor can be effectively solved.
Example two
As shown in fig. 6, when the number of the flow dividing pipes is equal to 1, the coolant flow passage includes a plurality of longitudinal pipes axially arranged along the stator housing, wherein a first longitudinal pipe is communicated with the water inlet 1, and a last longitudinal pipe is communicated with the water outlet 2; and in the other longitudinal pipelines, a connecting pipeline for communicating the two longitudinal pipelines is arranged between the two adjacent longitudinal pipelines, and the connecting pipelines are distributed in a staggered manner. The cross sections of the longitudinal pipelines and the connecting pipelines are rectangular. The equivalent diameter of the cooling liquid runner is gradually reduced from the water inlet 1 to the water outlet 2, so that the problem of uneven circumferential temperature of the motor can be effectively solved.
EXAMPLE III
As shown in fig. 7 and 8, when the number of the branch pipes is greater than 1, the coolant flow channel includes a plurality of branch pipes i connected to the water inlet 1, a plurality of branch pipes ii connected to the water outlet 2, a confluence pipe i for guiding the coolant flowing from the water inlet 1 to the branch pipes i, a confluence pipe ii for guiding the coolant flowing from the branch pipes i to the branch pipes ii, and a confluence pipe iii for guiding the coolant flowing from the branch pipes ii to the water outlet 2; the first shunt pipelines and the second shunt pipelines form a plurality of shunt pipelines, each shunt pipeline is arranged along the circumferential direction of the stator shell 3, and the shunt pipelines are uniformly distributed along the axial direction of the stator shell 3; the equivalent diameters of the same shunt pipeline are the same, and the equivalent diameters of the plurality of shunt pipelines change along the axial direction of the stator shell. The first confluence pipeline, the second confluence pipeline and the third confluence pipeline are all distributed along the axial direction of the stator shell, and the equivalent diameters of the first confluence pipeline, the second confluence pipeline and the third confluence pipeline are the same. The cross sections of the first diversion pipeline, the second diversion pipeline, the first confluence pipeline, the second confluence pipeline and the third confluence pipeline are all rectangular. The cooling liquid flows in from the water inlet, the confluence pipeline I distributes the cooling liquid to the shunt pipelines I, the cooling liquid flows for a circle in the shunt pipelines I and then is collected by the confluence pipeline II and redistributed to the shunt pipelines II, and the cooling liquid flows for a circle in the shunt pipelines II and then is collected by the confluence pipeline III, then enters the shunt pipelines at the outermost side and flows out from the water outlet. The equivalent diameter of the shunting pipeline and the number of the shunting pipelines are variable values, and the flow velocity of the cooling liquid is gradually increased from the water inlet to the water outlet.
The design principle of the invention is as follows:
in an electric machine cooling system, convective heat transfer can be described as:
Φh＝hAΔt (7)
wherein phihH is the convective heat transfer coefficient, A is the contact area between the wall surface of the cooling liquid flow channel and the cooling liquid, delta t is the temperature difference between the wall surface of the cooling liquid flow channel and the cooling liquid, v is the kinematic viscosity of the cooling liquid, and dlIs a characteristic diameter, N is the number of the shunt pipes, lpFor the total length of the coolant flow channel, μ is the hydrodynamic viscosity of the coolant, CpThe specific heat capacity at constant pressure is the thermal conductivity of the stator housing material, and Q is the input flow to the cooling system. When the cooling system pipeline is a single pipe, N is 1, namely, the cooling liquid flow channel described in the first embodiment and the second embodiment.
In the cooling liquid flow channel, the temperature of the cooling liquid increases from the water inlet 1 to the water outlet 2, so the temperature difference delta t between the wall surface temperature of the cooling liquid flow channel and the cooling liquid decreases progressively, h x A can be increased by adopting the design method and the cooling liquid flow channel structure, and the heat dissipation phi of each section of the cooling system is maintainedhThe value of (A) is in a certain range, so that the temperature of each part of the motor is uniform. Simulation results show that the heat dissipation performance at the position is better as the flow speed is increased.
In the formula (8), the length Δ l of the pipe infinitesimal is takenpTo calculate the area, there are:
the heat dissipation capacity of the water inlet is phi1＝h1A1Delta t, delta t is the temperature difference between the cooling liquid at the water inlet and the wall surface, and the equivalent diameter is taken as d1(ii) a The heat dissipation at the water outlet is phi2＝h2A2(delta T-delta T) which is the temperature difference between the cooling liquid at the water outlet and the wall surface, and the equivalent diameter is taken as d2. Let phi1＝Φ2After simplification, formula (6) is obtained:
wherein N is2The number of the shunt pipes connected with the water outlet in parallel is N1The number of the shunt pipes connected with the water inlet is in parallel. The equivalent diameter relation of the water inlet and the water outlet can be obtained according to the formula (6), reference is provided for the design of the whole cooling liquid flow channel, and the difference Y between the wall surface temperature of the water inlet and the wall surface temperature of the water outlet can reach the set precision Y through multiple iterations. Meanwhile, the parallel water channels can be segmented, and the temperature of each section of cooling liquid in the water channel is measured by the temperature measuring module to obtain delta T, so that the relation between the equivalent diameter of each stage of flow dividing pipeline and the equivalent diameter of the water inlet is obtained, the accuracy of the heat dissipation capacity in the water channel is improved, and the temperatures of all parts of the motor tend to be consistent.
The above-mentioned embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solution of the present invention by those skilled in the art should fall within the protection scope defined by the claims of the present invention without departing from the spirit of the present invention.
Claims (9)
1. The design method of the cooling system of the high-power density motor is characterized by comprising the following steps: the method comprises the following steps:
(1) a cooling liquid flow channel is arranged in the motor stator shell, a water inlet and a water outlet which are communicated with the cooling liquid flow channel are arranged on the outer side of the motor stator shell, and the initial sizes of the water inlet and the water outlet are set; the coolant flow channel comprises at least one split flow channel;
(2) obtaining parameters of the motor under rated working condition, and calculating the winding resistance loss P of the motor under rated working condition by the following formulaCuAnd core loss PFe：
PCu＝mI2R (1)
PFe＝Pn+Pc(2)
Pn＝KnfBp x(3)
Pc＝Kcf2BP 2(4)
Wherein m is the phase number, I is the rated current, and R is the resistance value of the motor winding; pnFor hysteresis loss, pcIs the eddy current loss; b ispIs the magnetic flux density amplitude, KnAnd x is the hysteresis loss coefficient, KcIs the eddy current loss coefficient, and f is the frequency of the alternating current;
using the formula P ═ PFe+PCuSolving the total loss P of the motor;
(3) the temperature difference delta T of the cooling liquid between the water inlet and the water outlet is obtained by adopting the following formula:
wherein p is the total loss of the motor, Q is the flow rate of the cooling liquid, rho is the density of the cooling liquid, and c is the specific heat capacity of the cooling liquid;
(4) the geometrical relationship between the water inlet and the water outlet is obtained by adopting the following formula:
wherein d is1Is the equivalent diameter of the water inlet, d2Is the equivalent diameter of the water outlet, N2The number of the shunt pipes connected with the water outlet in parallel is N1The number of the shunt pipes connected with the water inlet is in parallel connection, delta T-delta T is the temperature difference between the cooling liquid at the water outlet and the wall surface, and delta T is the temperature difference between the cooling liquid at the water inlet and the wall surface;
(5) and obtaining the optimal sizes of the water inlet and the water outlet through multiple iterations, so that the difference Y between the wall temperature of the water inlet and the wall temperature of the water outlet reaches the set precision Y.
2. The design method of the cooling system of the high power density motor according to claim 1, wherein: the step (5) of obtaining the optimal sizes of the water inlet and the water outlet through multiple iterations to enable the difference Y between the wall temperature of the water inlet and the wall temperature of the water outlet to reach the set precision Y comprises the following specific processes:
(51) acquiring the wall surface temperature difference y between the water outlet and the water inlet;
(52) solving the relation between the equivalent diameters of the water inlet and the water outlet by adopting a formula (6), and modifying the size of the water outlet according to the relation between the equivalent diameters of the water inlet and the water outlet;
(53) acquiring the wall surface temperature difference y between the water inlet and the water outlet again;
(54) and judging whether Y is smaller than the set precision Y, if so, outputting the sizes of the water inlet and the water outlet by taking the sizes of the current water inlet and the current water outlet as the optimal sizes of the water inlet and the water outlet, and if not, returning to the step (52).
3. A motor designed by the method for designing a cooling system of a high power density motor according to claim 1, wherein: the motor comprises a stator assembly, a rotor assembly and a cooling system; the cooling system comprises a cooling liquid flow channel arranged in the stator shell and a water inlet and a water outlet which are respectively arranged on the outer side of the stator shell; the coolant flow channel comprises at least 1 flow dividing pipeline connected between the water inlet and the water outlet.
4. The electric machine of claim 3, wherein: when the number of the flow dividing pipelines is equal to 1, the cooling liquid pipeline comprises a spiral pipeline which is connected between the water inlet and the water outlet and is coaxially arranged with the stator shell, and the central line of the spiral pipeline is superposed with the axial central line of the stator shell; the equivalent diameter of the spiral pipeline is gradually reduced from the water inlet to the water outlet; the cross section of the spiral pipeline is rectangular.
5. The electric machine of claim 3, wherein: when the number of the flow dividing pipelines is equal to 1, the cooling liquid flow channel comprises a plurality of longitudinal pipelines which are axially arranged along the stator shell, wherein the first longitudinal pipeline is communicated with the water inlet, and the last longitudinal pipeline is communicated with the water outlet; among other longitudinal pipelines, a connecting pipeline for communicating the two longitudinal pipelines is arranged between the two adjacent longitudinal pipelines, and the connecting pipelines are distributed in a staggered manner; the equivalent diameter of the cooling liquid flow channel is gradually reduced from the water inlet to the water outlet; the cross sections of the longitudinal pipelines and the connecting pipelines are rectangular.
6. The electric machine of claim 3, wherein: when the number of the diversion pipelines is more than 1, the cooling liquid flow channel comprises a plurality of diversion pipelines I connected with the water inlet, a plurality of diversion pipelines II connected with the water outlet, a confluence pipeline I used for guiding the cooling liquid flowing in from the water inlet to the diversion pipelines I, a confluence pipeline II used for guiding the cooling liquid in the diversion pipelines I to the diversion pipelines II and a confluence pipeline III used for guiding the cooling liquid in the diversion pipelines II to the water outlet; the first shunt pipelines and the second shunt pipelines form a plurality of shunt pipelines, each shunt pipeline is arranged along the circumferential direction of the stator shell, and the shunt pipelines are uniformly distributed along the axial direction of the stator shell; the equivalent diameters of the same shunt pipeline are the same, and the equivalent diameters of the plurality of shunt pipelines change along the axial direction of the stator shell.
7. The electric machine of claim 3, wherein: the stator assembly comprises a stator yoke and a stator shell which are coaxially arranged from inside to outside in sequence, stator teeth arranged on the inner wall of the stator yoke and stator windings wound on the stator teeth; the rotor assembly comprises a rotor yoke and a plurality of permanent magnets adhered to the outer wall of the rotor yoke; gaps are arranged between the adjacent permanent magnets; the permanent magnet is in an arc shape matched with the rotor yoke; the permanent magnet adopts a block type structure and comprises a plurality of small permanent magnets which are bonded and connected.
8. The electric machine of claim 5, wherein: the first confluence pipeline, the second confluence pipeline and the third confluence pipeline are all distributed along the axial direction of the stator shell, and the equivalent diameters of the first confluence pipeline, the second confluence pipeline and the third confluence pipeline are the same.
9. The electric machine of claim 5, wherein: the cross sections of the first diversion pipeline, the second diversion pipeline, the first confluence pipeline, the second confluence pipeline and the third confluence pipeline are all rectangular.
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| CN202010035149.9A CN111222279A (en) | 2020-01-14 | 2020-01-14 | Design method of high-power-density motor cooling system and motor designed by method |
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