A method and device for separating no-load loss of a permanent magnet generator
By using five opposing test platforms and temperature sensors under normal pressure and vacuum conditions, the losses of permanent magnet generators were isolated, solving the problem of difficult loss separation in existing technologies and realizing accurate loss measurement and design optimization.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NANJING TECH UNIV
- Filing Date
- 2022-11-08
- Publication Date
- 2026-05-12
AI Technical Summary
Existing technologies struggle to accurately separate various losses in permanent magnet generators, resulting in a lack of reliable pathways for verifying loss calculation models during the design process and impacting the accuracy of design optimization.
By combining five test platforms and temperature sensors under normal pressure and vacuum conditions, the input power and shaft heat of the generator were measured. Using torque sensors and generator windings under different conditions, bearing losses, rotor windage losses, winding copper losses, stator iron losses and rotor eddy current losses were isolated.
It achieves accurate measurement and separation of various types of losses, verifies the reliability of simulation and calculation models, improves the efficiency of generator system-level optimization design, and has low cost and simple operation.
Smart Images
Figure CN115864931B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to a generator loss separation method, in particular to a no-load loss separation method and device of a permanent magnet generator, and belongs to the technical field of generators. BACKGROUND
[0002] Permanent magnet motors have the advantages of high power density, high efficiency and good dynamic characteristics, and are widely used in electric spindles, new type flywheel energy storage and gas turbine power generation systems. The rotor magnetic field of a permanent magnet generator is established by permanent magnets, and various losses exist in the running process. First, the wind friction loss exists between the rotating parts and the surrounding medium (generally air in the general working environment) in the high-speed rotating process, and the size is related to the rotating speed, the physical properties of the medium and the surface roughness of the rotating parts, and the wind friction loss does not exist in a high vacuum environment. At the same time, the rotating parts and the fixed parts are connected through bearings, and there are rolling balls or rolling needles between the inner and outer channels of the bearings, and there is friction loss in the rotating process. In addition to the influence of the rotating speed, the bearing loss is also related to its own characteristics. Second, the stator core of the permanent magnet motor is usually made of high magnetic permeability materials, such as non-oriented electrical steel, and a considerable proportion of iron loss is generated in the alternating magnetic field. In addition, for permanent magnet motors with high frequency, the motor winding material is exposed to an alternating leakage magnetic field. Due to the existence of skin effect, eddy current exists in the conductor, and additional loss will be generated in the winding under no-load and load conditions. Finally, affected by space harmonics, tooth harmonics and current time harmonics, there is a certain harmonic magnetic field on the rotor, which induces more rotor eddy current loss in the conductive parts.
[0003] The above-mentioned losses often occur simultaneously in the permanent magnet motor, and are dispersedly distributed on each electromagnetic component, and it is difficult to directly measure and separate each loss by simple instruments. At present, the mechanical loss and electromagnetic loss of the motor can be separated by the false rotor method and the natural speed reduction method, but the internal components of the mechanical loss and the electromagnetic loss still cannot be effectively and accurately separated. Therefore, in actual engineering application, the performance test can only obtain the total loss and the comprehensive efficiency of the motor or the generator, and the influence of each type of loss cannot be analyzed separately. In the design process of the motor, the actual test results of each loss are needed to test and verify the related models and calculation methods. Due to the inability to accurately measure and separate each type of loss, the verification work of the loss calculation model still lacks a feasible path. Further, due to the lack of reliable loss model and test data, the accuracy of the optimization of the electromagnetic parameters in the design process is reduced. SUMMARY
[0004] In order to overcome the shortcomings of the prior art, the application provides a no-load loss separation method of a permanent magnet generator, which solves the problem that each type of loss of the generator is difficult to be separately separated and determined. The application also provides a no-load loss separation device of a permanent magnet generator.
[0005] The technical solution of this invention is as follows: A method for separating no-load losses in a permanent magnet generator, comprising the following steps:
[0006] Step 1: Under normal pressure, on the test platform, the generator is driven by the motor to rotate and the input power of the generator is measured and recorded as P1. In this step, the generator magnet is not magnetized and the three-phase winding of the generator is in an open-circuit and no-load state.
[0007] Step 2: Under vacuum conditions, on the test platform, the generator is driven by the motor to rotate, and the input power of the generator is measured and recorded as P2. In this step, the generator magnet is not magnetized, and the three-phase windings of the generator are in an open-circuit and no-load state.
[0008] Step 3: Under normal pressure, on the test platform, the generator is driven by the motor to rotate and the input power of the generator is measured and recorded as P3. In this step, the generator magnet is magnetized and the three-phase winding of the generator is in an open-circuit no-load state.
[0009] Step 4: In a vacuum environment, on a test platform, the generator is driven by an electric motor to rotate, and the input power of the generator is measured and recorded as P4. In this step, the generator magnet is magnetized and the three-phase windings of the generator are replaced with non-conductive materials.
[0010] Step 5: Under vacuum conditions, on the test platform, the generator is driven by the motor to rotate. The sum of the heat at both ends of the generator shaft is measured and recorded as P5. In this step, the generator magnet is magnetized, the generator three-phase winding is in an open-circuit no-load state, and the inner surface of the fixed parts and the outer surface of the rotating parts of the generator are coated with a low infrared emissivity coating.
[0011] Among them, the bearing loss is P2, and the rotor wind friction loss is calculated as Pfr=P1−P2, the winding copper loss is Pwi=P3−P4, the rotor eddy current loss is Ped=P5, and the stator core loss is PFe=P4−P1−P5.
[0012] Further, in step 5, the heat at both ends of the generator shaft is calculated from the temperatures measured by temperature sensors set at predetermined intervals at both ends of the generator shaft. Specifically, the heat at the front end of the shaft is Q1 = k*A*(T2−T1) / L1, and the heat at the rear end of the shaft is Q2 = k*A*(T4−T3) / L2, where k is the thermal conductivity of the shaft material, A is the cross-sectional area of the shaft, T1 and T2 are the temperatures measured by the temperature sensors at the front end of the shaft, L1 is the spacing between the temperature measuring points of the temperature sensors at the front end of the shaft, T3 and T4 are the temperatures measured by the temperature sensors at the rear end of the shaft, and L2 is the spacing between the temperature measuring points of the temperature sensors at the rear end of the shaft.
[0013] Furthermore, the input power of the generator measured in steps 1 to 4 is obtained by measuring the input torque Ts of the generator through a torque sensor. The input power P = Ts * n, where n is the rotational speed of the generator shaft.
[0014] Another technical solution of the present invention is a permanent magnet generator no-load loss separation device, comprising five counter-tow test platforms and a computing unit, wherein the five counter-tow test platforms include:
[0015] The first platform is used to measure the input power of a generator under normal pressure. The magnets of the generator on the first platform are not magnetized, and the three-phase windings of the generator are in an open-circuit, no-load state.
[0016] The second platform is used to measure the input power of a generator under vacuum conditions. It includes a vacuum chamber, in which the generator and motor of the test platform are placed. The magnet of the generator on the second platform is not magnetized, and the three-phase windings of the generator are in an open-circuit, no-load state.
[0017] The third platform is used to measure the input power of the generator under normal pressure. The generator magnets on the third platform are magnetized, and the three-phase windings of the generator are in an open-circuit, no-load state.
[0018] The fourth platform, used to measure the input power of a generator in a vacuum environment, includes a vacuum chamber. The generator and motor of the towing test platform are placed in the vacuum chamber. The magnet of the generator on the fourth platform is magnetized, and the three-phase windings of the generator are made of non-conductive material.
[0019] And the fifth platform, used to measure the heat at both ends of the generator shaft under vacuum conditions, including a vacuum chamber, in which the generator and motor of the drag test platform are placed, the magnet of the generator on the fifth platform is magnetized, the three-phase winding of the generator is in an open-circuit no-load state, and the inner surface of the fixed parts and the outer surface of the rotating parts of the generator are coated with a low infrared emissivity coating.
[0020] The computing unit is used to implement the above-mentioned method for separating no-load losses of permanent magnet generators.
[0021] Furthermore, in the five towing test platforms, the shafts of the generator and the motor are connected by couplings and torque sensors. The torque sensors are used to measure the shaft torque of the generator to calculate the input power.
[0022] Furthermore, the fifth platform includes temperature sensors spaced at predetermined intervals at both ends of the generator shaft. The temperatures measured by these temperature sensors are used to calculate the heat at both ends of the generator shaft in the fifth platform.
[0023] The advantages of the technical solution provided by this invention are as follows:
[0024] This invention's method is independent of motor parameters and does not require an empirically based loss model, making it applicable to generators of various power and speed levels. It enables precise measurement of various types of losses, verifying the reliability of simulation and calculation-related mathematical models and methods. Furthermore, based on the test results of various losses, it facilitates generator system-level optimization design research, improving overall efficiency.
[0025] The permanent magnet generator no-load loss separation device of the present invention can be implemented by simple modification of existing motor testing equipment. The device and loss separation method use torque and temperature sensors, eliminating the need for high-value testing instruments and thus reducing costs. Furthermore, the testing device and platform are versatile, easy to operate, and readily integrated into system testing. Attached Figure Description
[0026] Figure 1 The structure and configuration of the first platform of the no-load loss separation device in this embodiment of the invention;
[0027] Figure 2 The structure and configuration of the second platform of the no-load loss separation device in this embodiment of the invention;
[0028] Figure 3 The structure and configuration of the third platform of the no-load loss separation device in this embodiment of the invention;
[0029] Figure 4 The structure and configuration of the fourth platform of the no-load loss separation device in this embodiment of the invention;
[0030] Figure 5 The structure and configuration of the fifth platform of the no-load loss separation device in this embodiment of the invention;
[0031] Figure 6 This is a flowchart of the main steps of the no-load loss separation method in an embodiment of the present invention. Detailed Implementation
[0032] The present invention will be further described below with reference to embodiments, but these are not intended to limit the scope of the invention.
[0033] Please combine Figures 1 to 5 As shown, this embodiment relates to a method for separating the no-load loss of a permanent magnet generator, which is based on a permanent magnet generator no-load loss separation device. The permanent magnet generator no-load loss separation device includes five counter-tow test platforms and a computing unit. The five counter-tow test platforms are a first platform, a second platform, a third platform, a fourth platform, and a fifth platform.
[0034] The first platform includes a 15kW, 20000r / min electric motor 11 and a generator 12 of the same power and speed rating. The neodymium iron boron magnet 121 on the rotor of the generator 12 is not magnetized. The three-phase windings 122 of the generator 12 are in an open-circuit, no-load state. The electric motor 11 is driven by a vector controller 15. The generator 12 is driven to rotate by the electric motor 11, and the two are axially connected through a torque sensor 13 and a coupling 14. The other structures of the towing test platform are existing technologies and will not be described in detail here.
[0035] The second platform has the same structure and configuration as the first platform, including a 15kW, 20000r / min electric motor 21 and a generator 22 with the same power and speed rating. The rotor neodymium iron boron magnet 221 of the generator 22 is not magnetized. The three-phase windings 222 of the generator 22 are in an open-circuit, no-load state, and the electric motor 21 is driven by a vector controller 25. The generator 22 is driven to rotate by the electric motor 21, and the two are axially connected through a torque sensor 23 and a coupling 24. In addition, the second platform structure also includes a vacuum chamber 20. The entire structure described above is installed in the vacuum chamber 20, that is, the electric motor 21, the generator 22, the coupling 24 between them, and other structures are all housed in the vacuum chamber 20 and operate in a vacuum environment.
[0036] The third platform has the same structure as the first platform, including a 15kW, 20000r / min electric motor 31 and a generator 32 of the same power and speed rating. The three-phase windings 322 of the generator 32 are in an open-circuit, no-load state. The electric motor 31 is driven by a vector controller 35. The generator 32 is driven to rotate by the electric motor 31, and the two are axially connected through a torque sensor 33 and a coupling 34. Unlike the first platform, the rotor neodymium iron boron magnet 321 of the generator 32 is magnetized.
[0037] The fourth platform has a similar structure to the third platform, including a 15kW, 20000r / min electric motor 41 and a generator 42 with the same power and speed rating. The rotor of the generator 42 has a magnetized neodymium iron boron magnet 421, and the electric motor 41 is driven by a vector controller 45. The generator 42 is driven to rotate by the electric motor 41, and the two are axially connected via a torque sensor 43 and a coupling 44. Unlike the third platform, the three-phase windings 422 of the generator 42 are made of a non-conductive material. In this embodiment, nylon is chosen as the non-conductive material.
[0038] The fifth platform is structurally similar to the third platform, including a 15kW, 20000r / min electric motor 51 and a generator 52 of the same power and speed rating. The three-phase windings 522 of the generator 52 are in an open-circuit, unloaded state. The neodymium iron boron magnets 521 of the generator 52 rotor are magnetized. The electric motor 51 is driven by a vector controller 55. The generator 52 is driven to rotate by the electric motor 51, and the two are axially connected through a torque sensor 53 and a coupling 54. Similar to the second platform, it also includes a vacuum chamber 50. The entire structure described above is installed in the vacuum chamber 50, meaning that the electric motor, generator, coupling between them, and other structures are all housed in the vacuum chamber and operate in a vacuum environment. In addition, the inner surface 523 of the fixed component and the outer surface 524 of the rotating component of the generator 52 are coated with a low infrared emissivity coating. Four non-contact infrared thermometers 526, 527, 528 and 529 are arranged inside the generator 52 housing to measure the temperature of four sampling points on the rotating shaft. Two are arranged at the front end and two at the rear end of the rotating shaft, and a certain axial distance is maintained between the two non-contact infrared thermometers.
[0039] Based on the aforementioned device, a method for separating the no-load losses of a permanent magnet motor is proposed, achieving the separation of bearing losses Pbr, rotor windage losses Pfr, winding copper losses Pwi, stator iron losses PFe, and rotor eddy current losses Ped, as follows: Figure 6 As shown, the main steps include:
[0040] Step 1: In the first platform, the generator 12 is driven by the electric motor 11. The input torque Ts and speed n of the generator 12 are measured by the torque sensor 13, and the input power P1 = Ts * n is calculated. P1 is the sum of bearing loss Pbr and rotor windage loss Pfr, i.e., P1 = Pbr + Pfr;
[0041] Step 2: For the second platform installed in the vacuum chamber 20, the generator 22 is rotated by the motor 21. The input torque Ts and rotational speed n of the generator 22 are measured by the torque sensor 23, and the input power P2 = Ts * n is calculated. Since it is in a vacuum environment, there is no wind friction loss Pfr, and P2 is the bearing loss Pbr, i.e., Pbr = P2. The difference between P1 and P2 is the rotor wind friction loss Pfr, i.e., Pfr = P1 − P2;
[0042] Step 3: In the third platform, the generator 32 is driven by the motor 31 to rotate. The input torque Ts and speed n of the generator 32 are measured by the torque sensor 33, and the input power P3 = Ts * n is calculated. At this time, P3 is the sum of bearing loss Pbr, rotor windage loss Pfr, winding copper loss Pwi, stator iron loss PFe, and rotor eddy current loss Ped, that is, P3 = Pbr + Pfr + Pwi + PFe + Ped;
[0043] Step 4: For the fourth platform, the generator 42 is rotated by the motor 41. The input torque Ts and rotational speed n of the generator 42 are measured by the torque sensor 43, and the input power P4 = Ts * n is calculated. At this time, since the winding 422 of the generator 42 is made of non-conductive nylon material, P4 includes bearing loss Pbr, rotor windage loss Pfr, stator iron loss PFe, and rotor eddy current loss Ped, but there is no winding copper loss Pwi, that is, P4 = Pbr + Pfr + PFe + Ped. Therefore, according to the measurement results of step 3, the difference between P3 and P4 is the winding copper loss Pwi, that is, Pwi = P3 − P4;
[0044] Step 5: For the fifth platform installed in the vacuum chamber 50, the generator 52 is rotated by the motor 51. Four infrared thermometers 526-529 are used to measure the temperatures T1, T2, T3, and T4 at four sampling points at the front and rear ends of the rotating shaft 525, respectively. Based on the measured temperatures T1-T4, the thermal conductivity k of the shaft material, and the cross-sectional area S of the shaft, the heat transferred at the front end Q1 = k*A*(T2−T1) / L1 and the heat transferred at the rear end Q2 = k*A*(T4−T3) / L2 are calculated, where L1 is the axial distance between thermometers 526 and 527, and L2 is the axial distance between thermometers 528 and 529. Since the inner cavity of generator 52 is in a high vacuum state and is coated with a low emissivity material, thermal convection, thermal radiation and thermal conduction between the stator and rotor are eliminated. The sum of the heat Q1 and Q2 transferred on the shaft (denoted as P5) is the rotor eddy current loss Ped, that is, Ped=P5=Q1+Q2.
[0045] The final analysis shows that the difference between the measured losses P4 and P1 (denoted as P6) is the sum of the stator iron loss PFe and the rotor eddy current loss Ped, i.e., P6 = P4 - P1 = PFe + Ped. Therefore, the difference between losses P6 and P5 is the core loss PFe, i.e., PFe = P6 - P5.
[0046] This embodiment uses the no-load loss separation device and method proposed in this invention to achieve accurate separation of bearing loss, wind friction loss, winding loss, stator iron loss and rotor eddy current loss of permanent magnet motor, which can be used to verify relevant model algorithms in simulation and calculation process.
Claims
1. A method for separating no-load losses in a permanent magnet generator, characterized in that, Includes the following steps: Step 1: Under normal pressure, on the test platform, the generator is driven by the motor to rotate and the input power of the generator is measured and recorded as P1. In this step, the generator magnet is not magnetized and the three-phase winding of the generator is in an open circuit and no-load state. Step 2: Under vacuum conditions, on the test platform, the generator is driven by the motor to rotate, and the input power of the generator is measured and recorded as P2. In this step, the generator magnet is not magnetized, and the three-phase windings of the generator are in an open-circuit and no-load state. Step 3: Under normal pressure, on the test platform, the generator is driven by the motor to rotate and the input power of the generator is measured and recorded as P3. In this step, the generator magnet is magnetized and the three-phase winding of the generator is in an open-circuit no-load state. Step 4: In a vacuum environment, on a test platform, the generator is driven by an electric motor to rotate, and the input power of the generator is measured and recorded as P4. In this step, the generator magnet is magnetized and the three-phase windings of the generator are replaced with non-conductive materials. Step 5: Under vacuum conditions, on the test platform, the generator is driven by the motor to rotate. The sum of the heat at both ends of the generator shaft is measured and recorded as P5. In this step, the generator magnet is magnetized, the generator three-phase winding is in an open-circuit no-load state, and the inner surface of the fixed parts and the outer surface of the rotating parts of the generator are coated with a low infrared emissivity coating. Among them, the bearing loss is Pbr, Pbr=P2, the rotor wind friction loss is calculated as Pfr=P1-Pbr=P1−P2, the winding copper loss is Pwi=P3−P4, the rotor eddy current loss is Ped=P5, and the stator core loss is PFe= P4−P1−P5.
2. The method for separating no-load losses of a permanent magnet generator according to claim 1, characterized in that, In step 5, the heat at both ends of the generator shaft is calculated from the temperatures measured by temperature sensors set at predetermined intervals at both ends of the generator shaft. Specifically, the heat at the front end of the shaft is Q1 = k*A*(T2−T1) / L1, and the heat at the rear end of the shaft is Q2 = k*A*(T4−T3) / L2, where k is the thermal conductivity of the shaft material, A is the cross-sectional area of the shaft, T1 and T2 are the temperatures measured by the temperature sensors at the front end of the shaft, L1 is the spacing between the temperature measuring points of the temperature sensors at the front end of the shaft, T3 and T4 are the temperatures measured by the temperature sensors at the rear end of the shaft, and L2 is the spacing between the temperature measuring points of the temperature sensors at the rear end of the shaft.
3. The method for separating no-load losses of a permanent magnet generator according to claim 1, characterized in that, The input power of the generator measured in steps 1 to 4 is obtained by measuring the input torque Ts of the generator using a torque sensor. The input power P = Ts * n, where n is the rotational speed of the generator shaft.
4. A permanent magnet generator no-load loss separation device, characterized in that, It includes five towing test platforms and a computing unit, wherein the five towing test platforms include: The first platform is used to measure the input power of a generator under normal pressure. The magnets of the generator on the first platform are not magnetized, and the three-phase windings of the generator are in an open-circuit, no-load state. The second platform is used to measure the input power of a generator under vacuum conditions. It includes a vacuum chamber, in which the generator and motor of the test platform are placed. The magnet of the generator on the second platform is not magnetized, and the three-phase windings of the generator are in an open-circuit, no-load state. The third platform is used to measure the input power of the generator under normal pressure. The generator magnets on the third platform are magnetized, and the three-phase windings of the generator are in an open-circuit, no-load state. The fourth platform, used to measure the input power of a generator in a vacuum environment, includes a vacuum chamber. The generator and motor of the towing test platform are placed in the vacuum chamber. The magnet of the generator on the fourth platform is magnetized, and the three-phase windings of the generator are made of non-conductive material. And the fifth platform, used to measure the heat at both ends of the generator shaft under vacuum conditions, including a vacuum chamber, in which the generator and motor of the drag test platform are placed, the magnet of the generator on the fifth platform is magnetized, the three-phase winding of the generator is in an open-circuit no-load state, and the inner surface of the fixed parts and the outer surface of the rotating parts of the generator are coated with a low infrared emissivity coating. The computing unit is used to implement the permanent magnet generator no-load loss separation method as described in any one of claims 1 to 3.
5. The permanent magnet generator no-load loss separation device according to claim 4, characterized in that, In the five towing test platforms, the shafts of the generator and the motor are connected by couplings and torque sensors. The torque sensors are used to measure the shaft torque of the generator to calculate the input power.
6. The permanent magnet generator no-load loss separation device according to claim 4, characterized in that, Temperature sensors at predetermined intervals are installed at both ends of the generator shaft in the fifth platform. The temperatures measured by these temperature sensors are used to calculate the heat at both ends of the generator shaft in the fifth platform.