Method for calculating stator iron loss of permanent magnet motor

Abstract

The invention relates to a method for calculating stator iron loss of a permanent magnet motor, which uses a test motor, an unmagnetized motor and a to-be-tested motor with the same winding, and comprises the following steps: S1, connecting a rotating shaft of the test motor with a rotating shaft of the unmagnetized motor, controlling the test motor to drive the rotating speed of the rotating shaft of the unmagnetized motor to be increased to V1 by a driver, recording the input power P1 of the test motor and the winding temperature T1 of the unmagnetized motor; s2, when the to-be-tested motor runs in a no-load mode, the driver controls the rotating speed of a rotating shaft of the to-be-tested motor to be increased to V1 and the winding temperature of the to-be-tested motor to be T1, and the input power P2 of the to-be-tested motor and the winding current I of the to-be-tested motor are recorded; s3, calculating copper loss P3 according to the winding current I of the motor to be measured; and S4, P4 = P2-P1-P3, and P4 is the stator iron loss. According to the scheme, the iron loss of the permanent magnet motor can be accurately measured, and the iron loss and hysteresis coefficient of the stator core can be accurately calculated.

Description

Technical Field

[0001] The present invention relates to the technical field of motor design, and in particular to a method for calculating the stator iron loss of a permanent magnet motor. Background Art

[0002] Permanent magnet motors are widely used in many fields due to their high efficiency, high power density, low maintenance requirements and good dynamic response characteristics, such as industrial automation, new energy vehicles, wind power generation, household appliances, medical equipment, aerospace, agriculture, shipbuilding and marine engineering, compressors and pumps, etc. In the early design of permanent magnet motors, there will be a required efficiency value. In order to avoid repeated modifications due to insufficient design efficiency, the iron loss of permanent magnet motors needs to be calculated.

[0003] At present, there is no method that can accurately calculate the iron loss of a permanent magnet motor. The iron loss of the stator core of a permanent magnet motor mainly includes hysteresis loss, eddy current loss, and additional loss. Factors affecting iron loss include the material properties of silicon steel sheets, alternating frequency, magnetic field density, and material weight. Silicon steel sheets exhibit different magnetic properties due to the difference in raw materials, and their iron loss values ​​are different at different magnetic densities and frequencies. The prior art lacks a method that can accurately calculate the iron loss of the stator core of a permanent magnet motor.

[0004] Therefore, there is an urgent need for a method for calculating the stator iron loss of a permanent magnet motor to solve the above technical problems. Summary of the invention

[0005] The purpose of the present invention is to provide a method for calculating the stator iron loss of a permanent magnet motor, so as to accurately calculate the iron loss of the stator core of the permanent magnet motor.

[0006] To achieve the above object, the present invention provides a method for calculating the stator iron loss of a permanent magnet motor.

[0007] Using a test motor with identical windings, an unmagnetized motor, and a motor to be tested, the following steps are included:

[0008] S1: The rotating shaft of the test motor is connected to the rotating shaft of the unmagnetized motor. The driver controls the test motor to drive the rotating shaft of the unmagnetized motor to increase the rotation speed to V1. The input power P1 of the test motor and the winding temperature T1 of the unmagnetized motor are recorded.

[0009] S2: When the motor to be tested is running at no load, the driver controls the rotation speed of the shaft of the motor to be tested to increase to V1. When the winding temperature of the motor to be tested reaches T1, the input power P2 of the motor to be tested and the winding current I of the motor to be tested are recorded;

[0010] S3: Calculate the copper loss P3 according to the winding current I of the motor to be tested;

[0011] S4: According to P4=P2-P1-P3, where P4 is the stator iron loss.

[0012] Preferably, the step S2 further comprises: when the motor to be tested is in load operation, the rotating shaft of the motor to be tested is connected to the rotating shaft of the test motor, the driver controls the rotating speed of the rotating shaft of the motor to be tested to increase to V1, and when the winding temperature of the motor to be tested is T1, the input power P2' of the motor to be tested and the winding current I' of the motor to be tested are recorded;

[0013] The step S3 further includes: calculating the copper loss P3' according to the winding current I' of the motor to be tested;

[0014] The step S4 further includes: according to P4'=P2'-P1-P3', wherein P4' is the stator iron loss.

[0015] Preferably, V1 is 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500 and 8000 rpm respectively.

[0016] Preferably, the step S2 further comprises: when the motor to be tested is running at no-load, the driver controls the rotation speed of the shaft of the motor to be tested to increase to V1, and when the winding temperature of the motor to be tested increases from T1 to T2 and remains stable, the input power P2" of the motor to be tested, the winding current I" of the motor to be tested, the temperature T1 and the temperature T2 are recorded;

[0017] The step S3 also includes: calculating the copper loss P3" according to the winding current I" of the motor to be tested;

[0018] The step S4 also includes: according to P4"=P2"-P1-P3", wherein P4" is the stator iron loss.

[0019] As a preferred method, the winding phase resistance of the motor to be tested is measured, and the copper loss P3=3I 2 R, copper loss P3'=3I' 2 R, copper loss P3”=3I” 2 R*(1+α*(T2-T1)), where R is the phase resistance at the initial temperature, α is the temperature coefficient of resistance, T1 is the initial temperature, and T2 is the elevated temperature.

[0020] Preferably, when the motor to be tested is a plurality of identical motors to be tested, the method further comprises the steps of:

[0021] S5: Replace the motor to be tested, repeat S1 to S4, and calculate the iron loss of different motors to be tested.

[0022] Preferably, the method further includes step S6: weighing the stator core of the motor to be tested to obtain a weight m1, and the calculation formula of the stator iron loss is:

[0023] P Fe =[k h f m 2 +k c (fB m ) 2 +k e (fB m ) 1.5 ]*m1 / p,

[0024] Among them, k h is the hysteresis coefficient, k c is the eddy current coefficient, k e is the additional eddy current loss coefficient, f is the electrical frequency, B m is the maximum magnetic flux density, p is the material density of silicon steel sheet;

[0025] When P Fe When P4, P4', and P4" are used respectively, the hysteresis coefficient k is calculated. h The numerical value of .

[0026] Preferably, before step S1, step S0 is also included: selecting multiple motors to be tested, connecting the rotating shaft of the test motor to the rotating shaft of the motor to be tested, and controlling the test motor to run by a driver. When the rotating shaft speed of the motor to be tested is increased to V1, measuring the back EMF of the motor to be tested, and repeatedly measuring the back EMFs of other motors to be tested. If the back EMFs of multiple motors to be tested are consistent, they are used as motors to be tested; if there is a motor to be tested that has inconsistent back EMFs, replace the inconsistent motor to be tested.

[0027] Preferably, the step S0 also includes measuring the winding phase resistance R of multiple motors to be tested. If the winding phase resistance R of multiple motors to be tested is consistent, they are used as motors to be tested; if there is a motor to be tested whose winding phase resistance R is inconsistent, the inconsistent motor to be tested is replaced.

[0028] Preferably, the rotation speed V1 is detected by a non-contact sensor.

[0029] It can be seen from the above that the technical solution provided by the present invention can accurately measure the iron loss of the permanent magnet motor with high accuracy. According to the iron loss of the permanent magnet motor, the iron loss and hysteresis coefficient of the stator core can be accurately calculated, which is convenient for using the iron loss and hysteresis coefficient to design new motors. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a flow chart of a method for calculating stator iron loss of a permanent magnet motor according to an embodiment of the present invention;

[0031] Figure 2 A structural diagram of a test system used in a method for calculating the stator iron loss of a permanent magnet motor according to an embodiment of the present invention (used to detect the consistency of multiple motors to be tested);

[0032] Figure 3 A structural diagram of a test system used in a method for calculating stator iron loss of a permanent magnet motor according to an embodiment of the present invention (for detecting mechanical loss);

[0033] Figure 4 A structural diagram of a test system used in a method for calculating the stator iron loss of a permanent magnet motor according to an embodiment of the present invention (used to detect the total loss of the permanent magnet motor);

[0034] Figure 5 A structural diagram of a test system used in a method for calculating stator iron loss of a permanent magnet motor according to an embodiment of the present invention (for detecting mechanical loss);

[0035] Figure 6 A stator core structure diagram of a method for calculating stator iron loss of a permanent magnet motor according to an embodiment of the present invention.

[0036] In the figure:

[0037] 1. Motor to be tested; 2. Unmagnetized motor; 3. Test motor; 5. Coupling; 6. Temperature detection device; 7. Test bench;

[0038] 10. Stator core; 11. Stator yoke; 12. Stator teeth; 13. Stator root. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. It is understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It is also necessary to explain that, for ease of description, only the parts related to the present invention are shown in the accompanying drawings, rather than all.

[0040] Some directional words are defined in the present invention. Unless otherwise specified, the directional words used, such as "up", "down", "left", "right", "inside" and "outside", are used to facilitate understanding and therefore do not constitute a limitation on the scope of protection of the present invention.

[0041] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0042] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0043] This embodiment provides a method for calculating the stator iron loss of a permanent magnet motor. Figures 1 to 5 As shown, a motor to be tested 1, an unmagnetized motor 2, a test motor 3, a driver (not shown), a coupling 5, a temperature detection device 6, a test bench 7, a power analyzer (not shown) and a multimeter (not shown) are used, wherein the windings of the motor to be tested 1, the unmagnetized motor 2 and the test motor 3 are the same, and the following steps are included:

[0044] In this embodiment, the stator core material of the motor to be tested 1, the unmagnetized motor 2, and the test motor 3 is silicon steel sheet 35WW350, where the front 35 represents a nominal thickness of 0.35 mm, and 350 represents 100 times the maximum iron loss value of 3.50 W / kg.

[0045] The losses of permanent magnet motors mainly include copper loss, iron loss and mechanical loss. The copper loss and mechanical loss can be accurately obtained using test methods, but the iron loss is difficult to accurately obtain due to its characteristics.

[0046] Two groups of temperature testing devices are arranged at the winding ends of the motor 1 to be tested, and four groups of temperature testing devices are arranged on the outer surface of the casing to monitor the temperature change of the motor 1 to be tested.

[0047] S0: Select multiple motors to be tested, connect the shaft of test motor 3 to the shaft of motor 1 to be tested, and control the test motor 3 to run by a driver. When the shaft speed of motor 1 to be tested is increased to V1, measure the back EMF of motor 1 to be tested; repeatedly measure the back EMF of other multiple motors 1 to be tested. If the back EMFs of multiple motors 1 to be tested are consistent, use them as motor 1 to be tested; if there is a motor 1 to be tested that has inconsistent back EMFs, replace the inconsistent motor 1 to be tested.

[0048] like Figure 2 As shown, on the test bench 7, the rotating shaft of the motor 1 to be tested is connected to one end of the coupling 5, and the other end of the coupling 5 is connected to the rotating shaft of the test motor 3. The temperature detection device 6 on the motor 1 to be tested is used to monitor the temperature change of the motor 1 to be tested to ensure that the temperature of the motor 1 to be tested does not change too much. The driver controls the test motor 3 to operate, and the rotating shaft of the test motor 3 drives the rotating shaft of the motor 1 to be tested to rotate through the coupling 5. The rotating shaft drives the rotor core of the motor 1 to be tested to rotate. The magnetic field generated by the magnetic steel in the rotor core cuts the winding copper wire wound on the stator core to generate back electromotive force. The value of the back electromotive force of the motor 1 to be tested is measured by a multimeter. The temperature detection device 6 is connected to the power analyzer, and the temperature is displayed on the power analyzer. Replace another motor 1 to be tested, and repeat the test until the back electromotive force of multiple motors 1 to be tested is consistent.

[0049] The motor 1 to be tested is connected to the test motor 3 through a coupling, so that the test motor 3 drives the motor 1 to be tested to rotate, and the back EMF of the motor 1 to be tested is recorded once every 500 rpm. Similarly, test other motors 1 to be tested, compare the consistency of the back EMFs of the multiple motors 1 to be tested, and determine that the rotor magnetic properties of the multiple motors 1 to be tested are the same. If there is a motor 1 to be tested with a large back EMF deviation, replace it with a new motor 1 to be tested, and repeat the above test to ensure the consistency of the multiple motors 1 to be tested.

[0050] Selecting multiple motors to be tested also includes using a multimeter to measure the winding phase resistance R of multiple motors 1 to be tested. If the winding phase resistance R of multiple motors 1 to be tested is consistent, they are used as motors 1 to be tested; if there is a motor 1 to be tested that has inconsistent winding phase resistance R, replace the inconsistent motor 1 to be tested. For example, set the limit difference of the winding phase resistance R, compare the magnitude of the winding phase resistance R of multiple motors 1 to be tested, and if the difference is within the set error limit difference range, determine the winding consistency, if it exceeds the limit difference, replace the motor 1 to be tested, and repeat the above steps until it is determined that the multiple motors 1 to be tested are consistent. To ensure the reliability of the subsequent measured data. The winding phase resistance R measured in this process can be used as the winding phase resistance R at the initial temperature T1 for the subsequent calculation of copper loss.

[0051] S1: Reference Figure 3As shown, the rotating shaft of the test motor 3 is connected to the rotating shaft of the unmagnetized motor 2, and the driver controls the test motor 3 to drive the rotating shaft of the unmagnetized motor 2 to increase the rotation speed to V1, and records the input power P1 of the test motor 3 and the winding temperature T1 of the unmagnetized motor 2.

[0052] Unmagnetized motor 2 refers to a motor whose rotor is not magnetized. On the test bench 7, the unmagnetized motor 2 is connected to the test motor 3 through the coupling 5, and the test motor 3 is connected to the power analyzer. The test motor 3 drives the shaft of the unmagnetized motor 2 to rotate, and the rotation speed is increased to V1, and the input power P1 of the test motor 3 is recorded. The mechanical loss of the motor is positively correlated with the rotation speed. V1 is 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500, and 8000 rpm, that is, the data of the input power P1 displayed on the power analyzer is recorded once every 500rpm, and the input power P1 of the test motor 1 corresponding to different rotation speed conditions is recorded. Since the unmagnetized motor 2 is not magnetized, under this condition, the input power P1 of the test motor 1 is used as the mechanical loss of the motor 1 to be tested.

[0053] For the winding temperature T1 of the unmagnetized motor 2, a temperature measuring device can be used to detect the unmagnetized motor 2. Since the unmagnetized motor 2 has no current, the heat generated is very small, and the test time of the unmagnetized motor 2 is short. T1 can use the ambient temperature, that is, the ambient temperature is used as the initial temperature.

[0054] S2: Reference Figure 4 As shown, when the motor 1 to be tested is running at no load, the driver controls the rotation speed of the shaft of the motor 1 to be tested to increase to V1, and when the winding temperature of the motor 1 to be tested is T1, the input power P2 of the motor 1 to be tested and the winding current I of the motor 1 to be tested are recorded.

[0055] Take a motor 1 to be tested for no-load test. The motor 1 to be tested is connected to the power analyzer, and the driver controls the motor 1 to be tested to run at no-load. The rotation speed of the shaft of the motor 1 to be tested is increased to V1, and the winding temperature T1 of the motor 1 to be tested is obtained. The power analyzer will have data such as torque, speed, input power, output power, efficiency, current, etc., and record the input power P2 of the motor 1 to be tested and the winding current I of the motor 1 to be tested. Corresponding to the mechanical loss test of the unmagnetized motor 2, the V1 of the motor 1 to be tested is respectively 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500, and 8000 rpm, that is, the data of the input power P2 displayed on the power analyzer is recorded once every 500rpm. Since the main heat source iron loss will cause the temperature of the motor 1 to rise when the motor 1 is running at no load, thus affecting the magnetic properties of the motor 1, in this process, the temperature change of the motor 1 to be tested is monitored to make the winding temperature of the motor 1 to be tested at T1, where T1 is preferably an upper and lower deviation of no more than 2K (i.e., the floating deviation does not exceed 4K) to ensure the validity of the data. If the upper and lower floating extreme values ​​of the displayed temperature exceed 4K, the data is discarded, and the motor 1 to be tested is restored to temperature T1 for retesting.

[0056] When the shaft of the motor 1 to be tested rotates, it needs to overcome the friction caused by its own bearing and the periodically changing tooth slot torque. The loss caused by overcoming friction is mechanical loss, so there will be current display on the power analyzer when it is running at no load. At this time, the input power P2 displayed on the power analyzer is the sum of the motor iron loss P4 and the motor mechanical loss P1, which also includes a small part of the copper loss P3 caused by the current, which can be calculated using the formula for copper loss, and this part of the loss is removed for calculation.

[0057] S3: Calculate the copper loss P3 according to the winding current I of the motor 1 to be tested. In this embodiment, the winding phase resistance R of the motor 1 to be tested is measured at the initial temperature T1, and the calculation formula of the copper loss is P3=3I 2 R. In addition, since the no-load running current of the motor 1 to be tested is small, the value of the copper loss is small, and in some occasions where particularly accurate calculation is not required, the copper loss P3 can also be set to 0.

[0058] S4: According to P4=P2-P1-P3, P4 is the iron loss, P2 is the input power of the motor 1 to be tested when it is unloaded, and P1 is the input power when the test motor 3 drives the unmagnetized motor 2 to rotate. In the above test process, V1 takes 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500, 8000 rpm respectively, and multiple groups of corresponding P2, P1, and P3 are measured. Therefore, P4 also has multiple corresponding groups of values, and the corresponding values ​​are recorded.

[0059] The solution of the present invention can accurately measure the iron loss of the permanent magnet motor with high accuracy, and the iron loss and hysteresis coefficient of the stator core can be accurately calculated based on the iron loss of the permanent magnet motor. Therefore, the hysteresis coefficient is applied in the design of the new motor, and a new permanent magnet motor with high design accuracy is obtained by simulation, which reduces the project cycle and improves efficiency.

[0060] Preferably, in order to make the data more accurate, the driver used to control the test motor 3 and the driver used to control the motor to be tested 1 are the same driver.

[0061] Furthermore, step S2 further includes: referring to Figure 5 As shown, when the motor 1 to be tested is running under load, the shaft of the motor 1 to be tested is connected to the shaft of the test motor 3, and the driver controls the rotation speed of the shaft of the motor 1 to be tested to increase to V1. When the winding temperature of the motor 1 to be tested is T1, the input power P2' of the motor 1 to be tested and the winding current I' of the motor 1 to be tested are recorded.

[0062] The motor 1 to be tested is run under rated load. On the test bench 7, the rotating shaft of the motor 1 to be tested is connected to the rotating shaft of the test motor 3. The temperature detection device 6 on the motor 1 to be tested is used to detect the winding temperature of the motor 1 to be tested and the temperature of the casing, monitor the temperature change, and ensure that the motor temperature does not change too much, in order to keep the winding temperature of the motor 1 to be tested at T1. The driver controls the motor 1 to be tested to run under rated load, and the test motor 3 is used as the loading object. The motor 1 to be tested adjusts the speed while the rated current remains unchanged. The driver controls the rotation speed of the rotating shaft of the motor 1 to be tested to V1, and records the input power P2' of the motor 1 to be tested and the winding current I' of the motor 1 to be tested. V1 takes 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500, and 8000 rpm respectively, that is, the data of the input power P2' displayed on the power analyzer is recorded once every 500 rpm, and the corresponding input power P2' under different speed conditions is recorded as the total loss of the motor 1 to be tested.

[0063] The step S3 also includes: calculating the copper loss P3' according to the winding current I' of the motor 1 to be tested, measuring the winding phase resistance R of the motor 1 to be tested at the initial temperature T1, and the copper loss P3'=3I' 2 R. Under load, the value of I' is no longer small, but a much larger current value than that under no-load. Therefore, P3' cannot be replaced by 0, and P3' should be calculated accurately.

[0064] The step S4 also includes: according to P4'=P2'-P1-P3', where P4' is the stator iron loss. In the above test process, V1 is respectively 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500, 8000 rpm, and multiple groups of corresponding P2, P1, and P3 are measured. Therefore, P4 also has multiple groups of corresponding values, and the corresponding values ​​are recorded.

[0065] The stator iron loss under load was further measured and the stator iron loss could be accurately calculated.

[0066] Furthermore, the step S2 further includes: referring to Figure 4 As shown, when the motor 1 to be tested is running at no-load, the driver controls the rotation speed of the shaft of the motor 1 to be tested to increase to V1, and the winding temperature of the motor 1 to be tested increases from the initial temperature T1 to the increased temperature T2 and remains stable, and the input power P2" of the motor 1 to be tested, the winding current I" of the motor 1 to be tested, the initial temperature T1 and the increased temperature T2 are recorded.

[0067] The driver controls the motor 1 to be tested to run at no load, and the rotation speed of the shaft of the motor 1 to be tested is increased to V1. The temperature detection device 6 on the motor to be tested, the motor 1 to be tested is connected to the power analyzer, and the power analyzer will display the parameters of the motor 1 to be tested. The temperature detection device 6 obtains the real-time temperature change of the motor 1 to be tested, and records the temperature data detected by the temperature detection device 6 every 3 minutes until the temperature rises from the initial temperature T1 to T2 within half an hour and the temperature rise does not exceed 1K. At this time, the temperature rise of the motor 1 to be tested reaches stability, that is, the winding temperature of the motor to be tested rises to T2 and remains stable. Record the input power P2" of the motor 1 to be tested, the winding current I" of the motor 1 to be tested, the initial temperature T1 and the increased temperature T2. Since this detection method has a long detection time, if the detection is performed every 500 revolutions, the workload is huge. In order to ensure the accuracy of the data and to reduce the measurement time, this detection method only takes data when the V1 speed is 3000 rpm.

[0068] The step S3 further includes: calculating the copper loss P3″ according to the winding current I″ of the motor 1 to be tested, wherein the winding phase resistance R of the motor 1 to be tested is measured, and the copper loss P3″=3I″2 R*(1+α*(T2-T1)), where α is the temperature coefficient of resistance, T1 is the initial temperature, T2 is the increased temperature, and R is the phase resistance at the initial temperature.

[0069] The step S4 also includes: according to P4"=P2"-P1-P3", wherein P4" is the stator iron loss.

[0070] The stator iron loss in the case where the temperature is changed from the initial temperature T1 to the elevated temperature T2 is further measured.

[0071] Preferably, the rotation speed V1 is detected by a non-contact sensor, for example, a Hall sensor is used to test the rotation speed, and multiple Hall sensors may be provided to ensure the accuracy of the data.

[0072] Furthermore, when the motor 1 to be tested is a plurality of identical motors 1 to be tested, the method further includes the following steps: S5: replacing the motor 1 to be tested, repeating steps S1 to S4, and calculating the iron loss of different motors 1 to be tested. In order to make the detected data more accurate, multiple motors 1 to be tested are used to repeat the above steps S1 to S4 respectively, and the corresponding P4, P4', and P4" are calculated. For example, three motors 1 to be tested are taken for testing, and the three motors 1 to be tested are numbered as motor 1-1 to be tested, motor 1-2 to be tested, and motor 1-3 to be tested, so as to facilitate recording and calculation and avoid errors and confusion.

[0073] The method for calculating the stator iron loss of the permanent magnet motor also includes step S6: weighing the stator iron core of the motor 1 to be tested to obtain a weight m1. The calculation formula of the iron loss is:

[0074] P Fe =[k h f m 2 +k c (fB m ) 2 +k e (fB m ) 1.5 ]*m1 / p,

[0075] Among them, k h is the hysteresis coefficient, k c is the eddy current coefficient, k e is the additional eddy current loss coefficient, f is the electrical frequency, B m is the maximum magnetic flux density value, and p is the material density of silicon steel sheet.

[0076] Eddy current coefficient k c After the material thickness and conductivity are determined, it is a fixed value, and the calculation formula is k c =π 2 *σ*d 2 / 6. The eddy current coefficient of silicon steel sheet varies according to its thickness. The eddy current coefficient k of silicon steel sheet with a thickness of 0.35 mm is c The eddy current coefficient k of the silicon steel sheet with a thickness of 0.5 mm is 0.4575 W / m3. c is 0.9336W / m3. Fe are P4, P4', P4", respectively, and the hysteresis coefficient k is calculated. h The numerical value of .

[0077] Hysteresis loss is the energy loss caused by the irreversible movement of the domain wall and the rotation of the magnetic domain when the ferromagnetic material is repeatedly magnetized in an alternating magnetic field; eddy current loss is the resistance loss caused by the eddy current induced in the ferromagnetic material by the alternating magnetic field; additional eddy current loss is other losses besides hysteresis loss and eddy current loss, which is usually related to factors such as the material's microstructure and impurities.

[0078] The additional eddy current loss accounts for a small proportion, and its influence on the iron loss can be ignored. Therefore, the main unknown in the iron loss calculation formula is the hysteresis coefficient. Taking the three sets of iron loss values ​​obtained from the test as the target values, the no-load iron loss of the simulation project is calculated, and the hysteresis coefficient is continuously solved using the least squares method to solve the hysteresis coefficient infinitely close to the target value.

[0079] Due to the influence of magnetic resistance, the magnetic field of permanent magnet motors will produce harmonics of different frequencies, and these harmonics will also produce iron loss. Although its magnetic density is small, its frequency is a multiple of the fundamental wave. According to the loss calculation formula, it will also have a significant impact. In addition, during the production and processing of the stator core, during the molding process, the mold will have a trimming edge effect on the core, which will destroy the structural characteristics of the core edge material, resulting in changes in the magnetic domain distribution of the core material at the edge and changes in the metallographic structure, resulting in an increase in this part of the iron loss.

[0080] The above-mentioned factors have a certain impact on the loss of permanent magnet motors. Because it is impossible for all dimensional parameters to be the same when designing the stator and rotor cores of each motor, a correction factor is required.

[0081] A series of hysteresis coefficients of the stator core are obtained according to the above calculations. The hysteresis coefficients can be applied to the simulation software system to perform simulation calculations on the newly designed motor.

[0082] Taking the motor no-load state as an example, activate the core loss algorithm in the simulation software, divide the stator core into grids, and refine the grids to make the iron loss value calculation more precise. Since the current is very small when no-load, the simulation current can be set to 0A. The iron loss generated on the stator core is caused by the alternating magnetic field caused by the rotation of the rotor permanent magnet. Run this project to obtain the iron loss value calculated by simulation.

[0083] like Figure 6As shown, the stator core 10 is divided into three parts, including a stator yoke 11, a stator tooth 12, and a stator root 13. The maximum magnetic density value of each part is found by using the probe function of the software. Then, the iron loss value of each part is calculated by combining the calculated weight of each part, the alternating frequency of the magnetic field, the hysteresis coefficient of the material, the eddy current coefficient, and the additional loss coefficient using the traditional iron loss calculation formula. The sum of the iron loss values ​​is the iron loss value calculated by the formula.

[0084] Comparing the simulated iron loss value with the calculated iron loss value, the difference is very small. It can be seen that the above calculation method can correct the simulation parameters of the core material, which has reference significance for the subsequent motor design scheme using the core. It can be seen that the software also uses the traditional calculation formula for the simulation of iron loss, but it has carried out grid division, dividing the stator core into more than N small units, and the calculation accuracy is higher. Therefore, the accuracy of the above method for calculating the stator iron loss of permanent magnet motor is verified. When designing a new permanent magnet motor, using silicon steel sheet 35WW350, the stator iron loss value calculated by the present invention can be applied to the simulation system to simulate the iron loss of the new permanent magnet motor, which can greatly save the design cycle.

[0085] Although the present invention has been described in detail above by means of general description, specific implementation methods and tests, it is obvious to those skilled in the art that some modifications or improvements may be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A method for calculating the stator iron loss of a permanent magnet motor, characterized in that: Using a test motor with identical windings, an unmagnetized motor, and a motor to be tested, the following steps are included: S1: The rotating shaft of the test motor is connected to the rotating shaft of the unmagnetized motor. The driver controls the test motor to drive the rotating shaft of the unmagnetized motor to increase the rotation speed to V1. The input power P1 of the test motor and the winding temperature T1 of the unmagnetized motor are recorded. S2: When the motor to be tested is running at no load, the driver controls the rotation speed of the shaft of the motor to be tested to increase to V1. When the winding temperature of the motor to be tested reaches T1, the input power P2 of the motor to be tested and the winding current I of the motor to be tested are recorded; S3: Calculate the copper loss P3 according to the winding current I of the motor to be tested; S4: According to P4=P2-P1-P3, where P4 is the stator iron loss.

2. The method for calculating the stator iron loss of a permanent magnet motor according to claim 1, characterized in that: The step S2 further comprises: when the motor under test is in load operation, the rotating shaft of the motor under test is connected to the rotating shaft of the test motor, the driver controls the rotating speed of the rotating shaft of the motor under test to increase to V1, and when the winding temperature of the motor under test is T1, the input power P2' of the motor under test and the winding current I' of the motor under test are recorded; The step S3 further includes: calculating the copper loss P3' according to the winding current I' of the motor to be tested; The step S4 further includes: according to P4'=P2'-P1-P3', wherein P4' is the stator iron loss.

3. The method for calculating the stator iron loss of a permanent magnet motor according to claim 2, characterized in that: in, The V1 is 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500 and 8000 rpm respectively.

4. The method for calculating the stator iron loss of a permanent magnet motor according to claim 3, characterized in that: The step S2 further comprises: when the motor to be tested is running at no-load, the driver controls the rotation speed of the shaft of the motor to be tested to increase to V1, and when the winding temperature of the motor to be tested increases from T1 to T2 and remains stable, the input power P2" of the motor to be tested, the winding current I" of the motor to be tested, the temperature T1 and the temperature T2 are recorded; The step S3 also includes: calculating the copper loss P3" according to the winding current I" of the motor to be tested; The step S4 also includes: according to P4"=P2"-P1-P3", wherein P4" is the stator iron loss.

5. The method for calculating the stator iron loss of a permanent magnet motor according to claim 4, characterized in that: The winding phase resistance of the motor to be tested is measured, and the copper loss P3 = 3I 2 R, copper loss P3'=3I' 2 R, copper loss P3”=3I” 2 R*(1+α*(T2-T1)), where R is the phase resistance at the initial temperature, α is the temperature coefficient of resistance, T1 is the initial temperature, and T2 is the elevated temperature.

6. The method for calculating the stator iron loss of a permanent magnet motor according to claim 5, characterized in that: When the motor to be tested is a plurality of identical motors to be tested, the method further includes the following steps: S5: Replace the motor to be tested, repeat S1 to S4, and calculate the iron loss of different motors to be tested.

7. The method for calculating the stator iron loss of a permanent magnet motor according to claim 6, characterized in that: The method further includes step S6: weighing the stator core of the motor to be tested to obtain a weight m1. The calculation formula of the stator iron loss is: P Fe =[k h fB m 2 +k c (fB m ) 2 +k e (fB m ) 1.5 ]*m1 / p, Among them, k h is the hysteresis coefficient, k c is the eddy current coefficient, k e is the additional eddy current loss coefficient, f is the electrical frequency, B m is the maximum magnetic flux density, p is the material density of silicon steel sheet; When P Fe When P4, P4', and P4" are used respectively, the hysteresis coefficient k is calculated. h The numerical value of .

8. The method for calculating the stator iron loss of a permanent magnet motor according to claim 6, characterized in that: Before step S1, step S0 is also included: selecting multiple motors to be tested, connecting the rotating shaft of the test motor to the rotating shaft of the motor to be tested, and controlling the test motor to run by a driver. When the rotating shaft speed of the motor to be tested is increased to V1, measuring the back EMF of the motor to be tested, and repeatedly measuring the back EMF of other motors to be tested. If the back EMFs of multiple motors to be tested are consistent, they are used as motors to be tested; if there is a motor to be tested that has inconsistent back EMFs, replace the inconsistent motor to be tested.

9. The method for calculating the stator iron loss of a permanent magnet motor according to claim 8, characterized in that: The step S0 also includes measuring the winding phase resistance R of multiple motors to be tested. If the winding phase resistance R of the multiple motors to be tested is consistent, they are used as motors to be tested; if there is a motor to be tested that has an inconsistent winding phase resistance R, replace the inconsistent motor to be tested.

10. The method for calculating the stator iron loss of a permanent magnet motor according to claim 1, characterized in that: The rotation speed V1 is detected by a non-contact sensor.

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