A motor iron loss measurement platform

Abstract

The present invention relates to a motor iron loss measurement platform, comprising a stator assembly, a rotor assembly, a measuring device and a test motor, wherein the measuring device is connected to the stator assembly or / and the rotor assembly, the test motor is connected to the rotor assembly, the rotor assembly is arranged inside the stator assembly, the stator assembly comprises a stator core and an armature winding, and is characterized in that: the stator core has the same structure as the stator core of the motor under test, a winding slot is arranged in the stator core, the armature winding is made of Litz wire or a thin wire, and is located in the winding slot of the stator core, the slot full rate of the armature winding in the winding slot is less than the slot full rate of the armature winding in the stator core winding slot of the motor under test, and the conductivity of the permanent magnet is lower than the conductivity of the permanent magnet in the motor under test. Compared with the prior art in which the motor under test is directly used for iron loss testing, the measuring platform of the present invention can effectively suppress the additional loss generated during the measurement process, making the test more accurate.

Description

Technical Field

[0001] The invention belongs to the field of motor measurement, and in particular relates to a motor iron loss measurement platform. Background Art

[0002] Iron loss, also known as core loss, is a type of motor loss, which is composed of eddy current loss and hysteresis loss caused by the alternation of the main magnetic field in the motor core. The size of the core loss depends on the core material, frequency and magnetic flux density. The iron loss is approximately proportional to the square of the magnetic flux density, of which the hysteresis loss is approximately proportional to the frequency, and the eddy current loss is approximately proportional to the square of the frequency. Iron loss is an important component of motor loss, especially for high-speed motors, which have a high operating frequency, resulting in a large proportion of iron loss in the loss of high-speed motors, so that iron loss will also have a direct impact on the temperature rise of various components of the motor.

[0003] In addition to frequency and magnetic flux density, iron loss is also related to the loss coefficient of the material. Since the loss coefficient varies with factors such as magnetic field frequency, magnetic field strength, and temperature, it is difficult to derive directly through theory, so it is usually obtained by fitting the measured loss curve. The traditional iron loss measurement method is to make the core material into a ring, and wind the primary coil and secondary coil around the ring. During measurement, the current passed through the primary coil and the voltage waveform induced by the secondary coil are first detected, and then the core loss of the ring is obtained through calculation. The measured core loss of the ring under different magnetic field frequencies and sizes is fitted to obtain various loss coefficients. Finally, the loss coefficient is input into the numerical calculation software to calculate the iron loss of the motor.

[0004] However, the magnetic field in the motor is much more complex than that in the ring. The magnetic fields of the motor core and the ring are completely different, resulting in different loss coefficients. The calculated motor iron loss is different from the actual value. Therefore, it is necessary to accurately measure the actual motor iron loss to correct the theoretical calculation model, which is of great significance for subsequent motor optimization design, temperature field analysis and other work.

[0005] In the existing improved iron loss measurement platform, the loss of the motor under test is directly measured to improve the accuracy of the motor iron loss measurement. For example, the Chinese patent with publication number CN105467223A discloses a core loss test system and method for electrical steel materials in a motor environment, including a prime mover, a motor under test, a hollow long shaft, a resistance strain torque speed tester, a temperature sensor and an electrical test device, wherein the prime mover and the motor under test share a hollow long shaft to achieve speed synchronization and torque transmission; the stator of the motor under test is replaceable, the rotor of the motor under test is sleeved on the hollow long shaft, the rotor is equipped with a temperature sensor, a resistance strain torque speed tester is fixedly installed on the hollow long shaft, one end of the hollow long shaft is used as a lead-out end and is provided with a brush slip ring, the temperature sensor and the resistance strain torque speed tester are both connected to the brush slip ring at the lead-out end of the hollow long shaft through the connection inside the hollow long shaft, and the brush slip ring is connected to the measuring bridge; the prime mover, the motor under test, the temperature sensor and the resistance strain torque speed tester are all connected to the electrical test device.

[0006] The above-mentioned measurement platform has improved the measurement accuracy of the motor iron loss to a certain extent, but the measured motor has other losses besides iron loss. First, the conductor has skin effect and proximity effect in the AC magnetic field, which causes AC copper loss, resulting in the actual copper loss being greater than the DC copper loss that can be directly measured; secondly, the currently more common high-performance permanent magnets are made of sintered NdFeB, sintered SmCo and other materials, with high conductivity. If the rotor is excited by permanent magnets, eddy current losses will be generated in the permanent magnets. In addition, the sheath, rotor yoke and shaft are also usually made of materials with high conductivity, which will generate eddy current losses. Among the above-mentioned types of additional losses, AC copper loss and permanent magnet eddy current loss account for a large proportion. In the process of iron loss measurement, these additional losses are difficult to separate from the iron loss, resulting in the measured loss being the sum of the iron loss and the additional loss, and the accurate value of the actual iron loss cannot be obtained. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a new motor iron loss measurement platform for the above-mentioned prior art, which can better suppress the AC copper loss and permanent magnet eddy current loss generated during the iron loss measurement process, thereby improving the measurement accuracy of the motor iron loss.

[0008] The technical solution adopted by the present invention to solve the above technical problems is: a motor iron loss measurement platform, including a stator assembly, a rotor assembly, a measuring device and a test motor, the measuring device is connected to the stator assembly or / and the rotor assembly, the test motor is connected to the rotor assembly, the rotor assembly is arranged inside the stator assembly, the stator assembly includes a stator core and an armature winding, and is characterized in that: the stator core has the same structure as the stator core of the motor to be measured, a winding slot is arranged in the stator core, the armature winding is made of Litz wire or a thin wire and is located in the winding slot of the stator core, the slot filling rate of the armature winding in the winding slot of the stator core of the motor to be measured is set to α, the slot filling rate of the armature winding in the motor to be measured in the winding slot of the stator core of the motor to be measured is set to β, the stator assembly satisfies: α is less than β; the rotor assembly includes a permanent magnet, a rotor yoke and a rotating shaft, the conductivity of the permanent magnet is set to σ1, the conductivity of the permanent magnet in the motor to be measured is set to σ2, and the following is satisfied: σ1<σ2 / 10.

[0009] Preferably, the winding slots in the stator core have openings, and the distribution position of the armature windings deviates from or is far away from the openings of the winding slots.

[0010] As an improvement, the permanent magnet is made of ferrite, bonded NdFeB or bonded SmCo, the rotor yoke is made of ceramic or plastic, and the size of the permanent magnet is larger than the size of the permanent magnet of the motor being measured. The permanent magnet is made of materials such as ferrite, bonded NdFeB, bonded SmCo, etc., and its electrical conductivity is less than one-tenth of that of the sintered permanent magnet, so the eddy current loss of the permanent magnet can be reduced. The rotor yoke is made of materials with low electrical conductivity such as ceramic or plastic to reduce the rotor yoke loss. Since the magnetic properties of the above-mentioned permanent magnet materials are weaker than those of traditional sintered NdFeB and sintered SmCo, and the rotor yoke material is non-magnetic, when the motor being measured uses sintered NdFeB or sintered SmCo, the size of the permanent magnet of the measuring platform of the present invention can be larger than the size of the permanent magnet of the motor being measured, so that the magnetic flux density in the stator core of the measuring platform is similar to the magnetic flux density in the stator core of the motor being measured.

[0011] As a further improvement, the permanent magnet adopts Halbach magnetization method to increase the magnetic flux density. When the rotor yoke is made of non-magnetic conductive material, the permanent magnet adopts Halbach magnetization method to achieve magnetic concentration effect.

[0012] Further improvement, the rotor is connected to the output shaft of the accompanying test motor through a coupling. When testing the no-load iron loss, the accompanying test motor drives the rotor assembly to rotate. When testing the loaded iron loss, the accompanying test motor provides the load torque. By adjusting the speed and torque of the accompanying test motor, the iron loss measurement under different working conditions can be achieved.

[0013] In a further improvement, a sheath is provided on the outer side of the rotor assembly, and the sheath is made of a material with low electrical conductivity such as carbon fiber or glass fiber. The sheath can ensure the mechanical strength of the rotor under high-speed operation. At the same time, in order to suppress the eddy current loss generated by the sheath and reduce the influence of the eddy current loss of the sheath on the iron loss measurement, the sheath should be made of a material with low electrical conductivity such as carbon fiber.

[0014] As a further improvement, the armature winding is powered by a multi-phase AC power supply, or by a frequency converter matched with the motor under test. When the frequency converter is used for power supply, the current of the measuring platform is closer to the current of the motor under test during actual operation, which can reflect the distortion of the actual current, thereby improving the iron loss measurement accuracy.

[0015] The rotating shaft of the rotor is made of a material with low electrical conductivity, such as ceramics and plastics, so as to suppress eddy current loss in the rotating shaft and improve the measurement accuracy of iron loss.

[0016] The measuring device is one or more of the following devices: an oscilloscope, a power analyzer, a torque and speed sensor, and a temperature sensor, wherein the oscilloscope is used to analyze the voltage and current waveforms of the armature winding, the power analyzer is used to analyze the power on the armature winding, the torque and speed sensor is used to analyze the power on the shaft, and the temperature sensor is used to analyze the temperature of each part of the measuring platform to ensure the safety of the measurement process.

[0017] The stator assembly, rotor assembly, measuring equipment and test motor are integrally located in a vacuum cover, so that the entire measuring platform is located in a vacuum environment, which can eliminate the wind friction loss generated when the rotor rotates and improve the iron loss measurement accuracy. At the same time, a magnetic suspension bearing can be used to achieve the suspension of the rotor to eliminate the loss caused by the mechanical friction of the bearing and further improve the iron loss measurement accuracy.

[0018] The stator assembly, rotor assembly, measuring equipment and accompanying test motor are integrally located in a high and low temperature test chamber. Since the motor under test will generate losses during actual operation, causing components to heat up, resulting in the stator core temperature of the motor under test being higher than the ambient temperature, and the size of the iron loss is closely related to the temperature of the core. Therefore, the measuring platform of the present invention can be placed in a high and low temperature test chamber to measure the stator iron loss at different temperatures and improve the iron loss measurement accuracy. When the measurement process takes a long time, the various components of the measuring platform will cause temperature rise due to losses. The temperature of each component of the measuring platform is controlled within a certain range by means of air cooling or water cooling to ensure the safety of the measurement process.

[0019] Compared with the prior art of directly testing the iron loss of the motor under test, the stator slot filling rate of the measuring platform of the present invention is lower, and the conductivity of the permanent magnet is lower. The stator assembly and the rotor assembly of the measuring platform of the present invention are used for iron loss measurement. Due to the improved design and materials, the AC copper loss and permanent magnet loss associated with the iron loss measurement process can be effectively suppressed, thereby effectively improving the measurement accuracy of the motor iron loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the structure of the motor iron loss measurement platform in an embodiment of the present invention.

[0021] Figure 2 The cross-sectional view of the motor under test.

[0022] Figure 3 4 is a cross-sectional view of a stator assembly and a rotor assembly in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below with reference to the accompanying drawings.

[0024] like Figure 1 The motor iron loss measurement platform shown includes a stator assembly 1, a rotor assembly 2, a test motor 3, a measuring device 4 and a motor under test 6. The motor under test 6 is not used directly for iron loss measurement, but is used to determine the size and structure of the stator assembly 1 and the rotor assembly 2. The rotor assembly 2 is connected to the test motor 3 through a coupling 5. By adjusting the speed and torque of the test motor 3, iron loss measurement under different working conditions can be achieved. The stator assembly 1 is arranged outside the rotor assembly 2. The measuring platform is located in a vacuum cover 7, which can eliminate the wind friction loss generated when the rotor rotates and improve the accuracy of iron loss measurement.

[0025] like Figure 2The figure shows a motor under test 6 with a common structure, including a motor under test stator assembly and a motor under test rotor assembly. The motor under test stator assembly includes a motor under test stator core 61 and a motor under test armature winding 62. The motor under test armature winding 62 is filled with winding slots in the motor under test stator core 61, and the slot filling rate is high, which can reduce the DC copper loss generated in the actual operation of the motor. The motor under test rotor assembly includes a motor under test permanent magnet 65, a motor under test rotor yoke 64, and a motor under test shaft 63. A motor under test sheath 66 is provided on the outside of the motor under test rotor assembly. The motor under test permanent magnet 65 is generally made of sintered NdFeB or sintered SmCo material, which can obtain stronger magnetic properties at a moderate price. The motor under test rotor yoke 64 is generally made of silicon steel sheet, electrical pure iron or magnetic steel, which is used to provide a magnetic field loop, reduce the magnetic resistance on the magnetic circuit, and enhance the performance of the motor. If the motor under test is directly loaded into the measuring platform for iron loss measurement, during the measurement process, since the wire cross-sectional area of ​​the armature winding 62 of the motor under test is large and the wire is close to the opening of the winding slot, the armature winding 62 of the motor under test will generate AC copper loss, and eddy current loss will also be generated in the permanent magnet 63 of the motor under test and the rotor yoke 64 of the motor under test. Ultimately, the measured loss is greater than the actual stator iron loss, resulting in measurement errors.

[0026] The structures of the stator assembly 1 and the rotor assembly 2 in this embodiment are shown in FIG. Figure 3 As shown, the stator 1 includes a stator core 11 and an armature winding 12. Figure 2 The structure and size of the stator core 61 of the motor under test are the same. The number of turns and the connection method of the armature winding 12 are the same as Figure 2 The armature winding 62 of the motor under test is the same as that of the motor under test, but a wire with a smaller cross-sectional area is used instead. Therefore, the slot fill rate of the armature winding 12 in the winding slot is lower than Figure 2 The slot filling rate of the armature winding 62 of the motor under test in the winding slot in the stator core 61 of the motor under test is reduced, and the wire is far away from the opening of the winding slot in the stator core 11. This design can effectively suppress the AC copper loss of the armature winding 12. It is worth noting that although this design will increase the DC copper loss of the armature winding 12 of the measurement platform, the DC copper loss can be calculated by the current on and the resistance when it is not powered, and the error effect on the iron loss measurement is very small.

[0027] The rotor assembly 2 includes a permanent magnet 23, a rotor yoke 22, and a rotating shaft 21. A sheath 24 is provided on the outer side of the rotor assembly 2. The permanent magnet 23 is made of a material with low electrical conductivity such as ferrite, bonded NdFeB, or bonded SmCo. The electrical conductivity of the permanent magnet 23 is set to σ1, and the electrical conductivity of the measured motor permanent magnet 65 is set to σ2, satisfying: σ1<σ2 / 10. The rotor yoke 22 is made of a material with low electrical conductivity such as ceramics and plastics, and the sheath 24 is made of a material with low electrical conductivity such as carbon fiber and glass fiber, thereby suppressing eddy current losses in the permanent magnet, rotor yoke, and sheath, and improving the accuracy of iron loss measurement. Figure 2 Compared with the motor under test in the present invention, the permanent magnet 23 of the measuring platform of the present invention has weaker performance, and the rotor yoke 22 is non-magnetic, and the magnetic resistance on the magnetic circuit is large. Therefore, in order to make the magnetic field strength and Figure 2 The magnetic field strength in the stator core 11 of the motor under test is similar, and the size of the permanent magnet 23 of the measuring platform of the present invention is larger than Figure 2 Furthermore, the permanent magnet 23 of the measuring platform of the present invention can adopt the Halbach magnetization method to improve the magnetic field concentration ability and increase the magnetic flux density in the stator core 11.

[0028] The measuring device is one or more of the following devices: an oscilloscope, a power analyzer, a torque and speed sensor, and a temperature sensor, wherein the oscilloscope is used to analyze the voltage and current waveforms of the armature winding, the power analyzer is used to analyze the power on the armature winding, the torque and speed sensor is used to analyze the power on the shaft, and the temperature sensor is used to analyze the temperature of each part of the measuring platform to ensure the safety of the measurement process.

[0029] If a normal motor is directly used for iron loss measurement, the measured loss is actually the sum of iron loss, DC copper loss, AC copper loss, permanent magnet loss, sheath loss, rotor yoke loss and shaft loss, among which DC copper loss can be accurately calculated, but the other types of losses cannot be separated from iron loss, resulting in the inability to measure the real iron loss. The stator and rotor of the measurement platform of the present invention are used for iron loss measurement. Due to the improved design and materials, the AC copper loss, permanent magnet loss, sheath loss, rotor yoke loss and shaft loss associated with the iron loss measurement process are effectively suppressed. The measured loss minus the DC copper loss is the real iron loss.

Claims

1. A motor iron loss measurement platform, comprising a stator assembly, a rotor assembly, a measuring device and a test motor, wherein the measuring device is connected to the stator assembly and / or the rotor assembly, the test motor is connected to the rotor assembly, the rotor assembly is arranged inside the stator assembly, the stator assembly comprises a stator core and an armature winding, and is characterized in that: The stator core has the same structure as the stator core of the motor under test, and winding slots are provided in the stator core. The armature winding is made of Litz wire or thin wire and is located in the winding slots of the stator core. The slot fill rate of the armature winding in the winding slots is set to α, and the slot fill rate of the armature winding in the motor under test in the winding slots of the stator core of the motor under test is set to β. The stator assembly satisfies: α is less than β; the rotor assembly includes a permanent magnet, a rotor yoke and a rotating shaft, the conductivity of the permanent magnet is set to σ1, the conductivity of the permanent magnet in the motor under test is set to σ2, and the following is satisfied: σ1<σ2 / 10.

2. The motor iron loss measurement platform according to claim 1, characterized in that: The winding slots in the stator core have openings, and the distribution positions of the armature windings deviate from or are far away from the openings of the winding slots.

3. The motor iron loss measurement platform according to claim 1, characterized in that: The permanent magnet is made of ferrite, bonded neodymium iron boron or bonded samarium cobalt, the rotor yoke is made of ceramic or plastic, and the size of the permanent magnet is larger than that of the permanent magnet of the motor being tested.

4. The motor iron loss measurement platform according to claim 3, characterized in that: The permanent magnet adopts the Halbach magnetization method.

5. The motor iron loss measurement platform according to claim 3, characterized in that: The rotor is connected to the output shaft of the accompanying test motor through a coupling.

6. The motor iron loss measurement platform according to claim 3, characterized in that: A sheath is arranged on the outer side of the rotor assembly, the sheath is made of carbon fiber or glass fiber, and the rotating shaft of the rotor is made of ceramic.

7. The motor iron loss measurement platform according to claim 1, characterized in that: The armature winding is powered by a multi-phase AC power supply or a frequency converter.

8. The motor iron loss measurement platform according to claim 1, characterized in that: The measuring device is one or more of the following devices: an oscilloscope, a power analyzer, a torque and speed sensor, and a temperature sensor, wherein the oscilloscope is used to analyze the voltage and current waveforms of the armature winding, the power analyzer is used to analyze the power on the armature winding, the torque and speed sensor is used to analyze the power on the shaft, and the temperature sensor is used to analyze the temperature of each part of the measuring platform to ensure the safety of the measurement process.

9. The motor iron loss measurement platform according to claim 1, characterized in that: The stator assembly, the rotor assembly, the measuring device and the accompanying test motor are integrally located in the vacuum cover.

10. The motor iron loss measurement platform according to claim 9, characterized in that: The stator assembly, rotor assembly, measuring equipment and accompanying test motor are integrally located in a high and low temperature test box.

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