Shaft voltage and shaft current calculation method and related device

Abstract

The invention provides a shaft voltage and shaft current calculation method and a related device, and the method comprises the steps: carrying out the static electric field finite element calculation of a simulation model of a motor, and obtaining the stray capacitance of the motor; calculating bearing equivalent capacitance based on the parameters of the bearing; performing common-mode impedance analysis on the motor to determine common-mode inductance; performing differential mode impedance analysis on the motor, and determining eddy current equivalent resistance; calculating an impedance parameter in a circulation axis current loop; based on the stray capacitance of the motor, the equivalent capacitance of the bearing, the common mode inductance, the eddy current equivalent resistance and the impedance parameters, an electrical model is built, and shaft current and shaft voltage at the two ends of the bearing are obtained through simulation. Different shaft current sources are considered, motor stray capacitance, bearing equivalent capacitance, common-mode inductance and eddy current equivalent resistance can influence EDM current, impedance parameters can influence circulating current, comprehensive consideration of the EDM current and the circulating current can be realized, the calculated shaft current and the calculated shaft current are more accurate, and the calculation efficiency is improved. And the use condition of the motor bearing can be evaluated more accurately.

Description

Technical Field

[0001] The present application relates to the field of motors, and in particular to a method for calculating shaft voltage and shaft current and a related device. Background Art

[0002] As new energy vehicles are developing towards high voltage platforms and high speeds, the problem of electrical corrosion in motor bearings is gradually emerging. Electrical corrosion is a phenomenon in which a large amount of heat is generated on the contact interface due to the instantaneous flow of current, causing local melting of metal materials and forming pits. Due to the presence of various currents in the motor, the electrical corrosion of the bearings is relatively serious, affecting the normal operation and service life of the bearings and even the motor. Therefore, it is necessary to accurately calculate the shaft voltage and shaft current of the bearing in order to monitor the use of the bearing. Summary of the invention

[0003] In view of this, the purpose of this application is to provide a method and related device for calculating shaft voltage and shaft current, so that the calculated shaft voltage and shaft current are more accurate and the use of motor bearings can be more accurately evaluated. The specific scheme is as follows:

[0004] On the one hand, the present application provides a method for calculating shaft voltage and shaft current, comprising:

[0005] Perform electrostatic field finite element calculation on the simulation model of the motor to obtain the stray capacitance of the motor;

[0006] Calculating the equivalent capacitance of the bearing based on the parameters of the bearing; the parameters of the bearing include the number of bearing balls, the diameter of the balls, the diameter of the inner ring of the bearing, the diameter of the outer ring of the bearing and the properties of the bearing material;

[0007] Performing common mode impedance analysis on the motor to determine common mode inductance;

[0008] Performing differential mode impedance analysis on the motor to determine eddy current equivalent resistance;

[0009] Calculating impedance parameters in the circulating shaft current loop; the impedance parameters include inductance, resistance, stator core path impedance and rotor lamination path impedance;

[0010] Based on the motor stray capacitance, the bearing equivalent capacitance, the common mode inductance, the eddy current equivalent resistance and the impedance parameters, an electrical model is built to simulate the shaft current and shaft voltage at both ends of the bearing.

[0011] Optionally, performing electrostatic field finite element calculation on the simulation model of the motor to obtain the stray capacitance of the motor includes:

[0012] Based on the physical structure of the motor, construct the simulation model of the motor;

[0013] Setting voltage boundary conditions; the voltage boundary conditions include the voltage boundary of the stator winding, the voltage boundary of the stator core and the voltage boundary of the rotor;

[0014] Based on the voltage boundary condition, electrostatic field finite element calculation is performed on the simulation model to obtain the motor stray capacitance; the motor stray capacitance includes a first capacitance between the stator winding and the housing, a second capacitance between the stator winding and the rotor, and a third capacitance between the housing and the rotor.

[0015] Optionally, the simulation model is a single-slot simulation model, and performing electrostatic field finite element calculation on the simulation model based on the voltage boundary condition to obtain the stray capacitance of the motor includes:

[0016] Performing electrostatic field finite element calculation on the single slot simulation model based on the voltage boundary condition to obtain the single slot stray capacitance;

[0017] The motor stray capacitance is determined based on the single-slot stray capacitance and the number of slots of the stator.

[0018] Optionally, performing common mode impedance analysis on the motor to determine common mode inductance includes:

[0019] Measuring the impedance between the three-phase stator winding and the housing to obtain a first corresponding relationship between the common mode impedance and the frequency;

[0020] Based on the first corresponding relationship, determining the port capacitance between the stator winding and the housing;

[0021] The common mode inductance is determined based on the first corresponding relationship and the port capacitance.

[0022] Optionally, determining the port capacitance between the stator winding and the casing based on the first corresponding relationship includes:

[0023] Determine the frequency and impedance corresponding to the phase angle of -90° from the first corresponding relationship;

[0024] The port capacitance between the stator winding and the housing is calculated according to the frequency and impedance corresponding to the phase angle of -90°.

[0025] Optionally, performing differential mode impedance analysis on the motor to determine eddy current equivalent resistance includes:

[0026] Measuring the impedance between the two-phase stator winding and the third-phase stator winding to obtain a second corresponding relationship between the differential mode impedance and the frequency;

[0027] Determine the impedance corresponding to the phase angle of 0° from the second corresponding relationship;

[0028] The eddy current equivalent resistance is calculated according to the impedance corresponding to the phase angle of 0°.

[0029] Optionally, the frequency range is 10 3 -10 6 Hz.

[0030] On the other hand, the embodiment of the present application further provides a device for calculating shaft voltage and shaft current, comprising:

[0031] A first calculation unit is used to perform electrostatic field finite element calculation on the simulation model of the motor to obtain the stray capacitance of the motor;

[0032] A second calculation unit is used to calculate the equivalent capacitance of the bearing based on the parameters of the bearing; the parameters of the bearing include the number of bearing balls, the diameter of the balls, the diameter of the inner ring of the bearing, the diameter of the outer ring of the bearing and the properties of the bearing material;

[0033] A first analysis unit, configured to perform common mode impedance analysis on the motor to determine common mode inductance;

[0034] A second analysis unit is used to perform differential mode impedance analysis on the motor to determine eddy current equivalent resistance;

[0035] A third calculation unit is used to calculate impedance parameters in the circulating shaft current loop; the impedance parameters include inductance, resistance, stator core path impedance and rotor lamination path impedance;

[0036] The simulation unit is used to build an electrical model based on the motor stray capacitance, the bearing equivalent capacitance, the common mode inductance, the eddy current equivalent resistance and the impedance parameter, and simulate the shaft current and shaft voltage at both ends of the bearing.

[0037] The present application provides a computer device, which includes a processor and a memory.

[0038] The memory is used to store program code and transmit the program code to the processor;

[0039] The processor is configured to execute the method described above according to the instructions in the program code.

[0040] On the other hand, an embodiment of the present application provides a computer-readable storage medium, wherein the computer-readable storage medium is used to store a computer program, and the computer program is used to execute the method described in the above aspects.

[0041] The embodiment of the present application provides a method and related device for calculating shaft voltage and shaft current, performs electrostatic field finite element calculation on a simulation model of a motor to obtain the stray capacitance of the motor; calculates the equivalent capacitance of the bearing based on the parameters of the bearing; the parameters of the bearing include the number of bearing balls, the ball diameter, the inner ring diameter of the bearing, the outer ring diameter of the bearing and the material properties of the bearing; performs common-mode impedance analysis on the motor to determine the common-mode inductance; performs differential-mode impedance analysis on the motor to determine the eddy current equivalent resistance; calculates the impedance parameters in the circulating shaft current loop; the impedance parameters include inductance, resistance, stator core path impedance and rotor lamination path impedance; based on the stray capacitance of the motor, the equivalent capacitance of the bearing, the common-mode inductance, the eddy current equivalent resistance and the impedance parameters, builds an electrical model, and simulates the shaft current and shaft voltage at both ends of the bearing. It can be seen that different sources of shaft current are considered in this application, among which the motor stray capacitance, bearing equivalent capacitance, common mode inductance and eddy current equivalent resistance will affect the EDM current, and the impedance parameters will affect the circulating current. Building a simulation model based on them can achieve comprehensive consideration of the EDM current and circulating current, making the calculated shaft current and shaft current more accurate, and can more accurately evaluate the usage of the motor bearings. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0043] Figure 1 A schematic flow chart of a method for calculating shaft voltage and shaft current provided in an embodiment of the present application is shown;

[0044] Figure 2 A schematic diagram of a simulation model of a motor provided in an embodiment of the present application is shown;

[0045] Figure 3 A wiring diagram of a common mode impedance test provided by an embodiment of the present application is shown;

[0046] Figure 4 A schematic diagram of a common-mode impedance curve provided in an embodiment of the present application is shown;

[0047] Figure 5 A wiring diagram of a differential mode impedance test provided by an embodiment of the present application is shown;

[0048] Figure 6 A schematic diagram of a differential mode impedance curve provided by an embodiment of the present application is shown;

[0049] Figure 7A schematic diagram of the structure of an electrical model provided in an embodiment of the present application is shown;

[0050] Figure 8 A structural block diagram of a shaft current and shaft voltage calculation device provided in an embodiment of the present application;

[0051] Fig. 9 A structural diagram of a computer device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0052] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below with reference to the accompanying drawings.

[0053] In the following description, many specific details are set forth to facilitate a full understanding of the present application, but the present application may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0054] The calculation method of shaft current and shaft voltage provided in the embodiment of the present application can be implemented by a computer device, which can be a terminal device or a server, wherein the server can be an independent physical server, or a server cluster or distributed system composed of multiple physical servers, or a cloud server providing cloud computing services. Terminal devices include but are not limited to mobile phones, computers, intelligent voice interaction devices, smart home appliances, vehicle-mounted terminals, etc. The terminal device and the server can be directly or indirectly connected via wired or wireless communication, and this application does not impose any restrictions on this.

[0055] For ease of understanding, a method for calculating shaft voltage and shaft current and related devices provided in an embodiment of the present application are described in detail below in conjunction with the accompanying drawings.

[0056] refer to Figure 1 As shown, it is a flow chart of a method for calculating shaft voltage and shaft current provided in an embodiment of the present application. The method may include the following steps.

[0057] S101, performing electrostatic field finite element calculation on the simulation model of the motor to obtain the stray capacitance of the motor.

[0058] Specifically, the simulation model of the motor can be created based on the physical structure of the motor, and the simulation model can be created in advance or newly created. The simulation model can be subjected to Maxwell-based electrostatic field finite element calculation to obtain the motor stray capacitance. The motor stray capacitance can be understood as the parasitic capacitance in the motor, which is the capacitance formed by the proximity of the components in the motor.

[0059] In a possible implementation, S101 may specifically include constructing a simulation model of the motor based on the physical structure of the motor; setting voltage boundary conditions; and performing electrostatic field finite element calculation on the simulation model based on the voltage boundary conditions to obtain the stray capacitance of the motor.

[0060] Specifically, the physical structure of the motor may include the structure of the motor stator and the structure of the motor rotor, etc. Based on the actual physical structure of the motor, a corresponding simulation model may be created. As an example, the simulation model may simulate the structure of the entire motor or may simulate the main part of the motor.

[0061] After the simulation model of the motor is created, voltage boundary conditions can be set for the simulation to ensure that the simulation process is normal. The voltage boundary conditions can include the voltage boundary of the stator winding, the voltage boundary of the stator core, and the voltage boundary of the rotor. As an example, the voltage boundary of the stator winding can be 1V, the voltage boundary of the stator core can be 0.5V, and the voltage boundary of the rotor can be 0V. In addition, the material properties can be assigned according to the actual materials of the stator and rotor components.

[0062] Under the voltage boundary condition, the simulation model can be simulated, and the capacitance coefficient matrix is ​​calculated during the simulation process to output the motor stray capacitance. The motor stray capacitance can include the first capacitance C between the stator winding and the housing. ws , the second capacitor C between the stator winding and the rotor rw , and the third capacitor C between the housing and the rotor rs .

[0063] Due to the interference fit between the stator core and the casing, the position and structure of the casing may not be shown in the simulation model. The first capacitance between the stator winding and the casing is also the capacitance between the stator winding and the stator core, and the third capacitance between the casing and the rotor is also the third capacitance between the stator core and the rotor.

[0064] Thus, by simulating and calculating these three types of stray capacitance in this way, a more accurate and comprehensive simulation of the motor stray capacitance can be obtained, which is convenient for the subsequent calculation of the shaft voltage and shaft current.

[0065] In one possible implementation, the simulation model is a single-slot simulation model, and electrostatic field finite element calculation is performed on the simulation model based on voltage boundary conditions to obtain the motor stray capacitance. Specifically, electrostatic field finite element calculation is performed on the single-slot simulation model based on voltage boundary conditions to obtain the single-slot stray capacitance; the motor stray capacitance is determined based on the single-slot stray capacitance and the number of slots in the stator.

[0066] In order to reduce the amount of calculation in the simulation process, the simulation model can be a single-slot simulation model, that is, the stator in the simulation model is a single slot, not a complete stator structure. Figure 2 , which is a schematic diagram of a simulation model of a motor provided in an embodiment of the present application, including a stator core, insulating paper, gaps, stator windings, insulating varnish, copper wedges, an air gap and a rotor (ie, a rotating shaft).

[0067] Furthermore, in the simulation calculation, the single-slot stray capacitance corresponding to the single-slot stator can be obtained, and then based on the single-slot stray capacitance and the number of stator slots, the motor stray capacitance under the complete stator structure can be obtained. As an example, the single-slot stray capacitance can be multiplied by the number of stator slots. In this way, the simulation accuracy can be guaranteed while reducing the simulation calculation amount, thereby shortening the simulation time.

[0068] S102, calculating the bearing equivalent capacitance based on the bearing parameters.

[0069] Specifically, the bearing equivalent capacitance can be calculated using the bearing_dianrong_calculation program according to the bearing parameters. The bearing parameters may include the number of bearing balls, the ball diameter, the bearing inner ring diameter, the bearing outer ring diameter, and the bearing material properties. The bearing material properties may include, for example, Poisson's ratio, elastic modulus, etc. Among them, the bearing equivalent capacitance may include the equivalent capacitance C of the left end bearing b,DE , and the equivalent capacitance C of the right end bearing b,NDE .

[0070] S103, performing common mode impedance analysis on the motor to determine common mode inductance.

[0071] Specifically, an impedance analyzer can be used to perform common-mode impedance analysis on the motor to accurately evaluate the shaft current and shaft voltage at high frequencies. When the motor is stationary, the bottom of the motor can be isolated with insulation and tested for common-mode impedance, thereby calculating the common-mode inductance.

[0072] In one possible implementation, common-mode impedance analysis is performed on the motor to determine the common-mode inductance. Specifically, the impedance between the three-phase stator winding and the casing is measured to obtain a first correspondence between the common-mode impedance and the frequency; based on the first correspondence, the port capacitance between the stator winding and the casing is determined; based on the first correspondence and the port capacitance, the common-mode inductance is determined.

[0073] Specifically, the two ends of the impedance analyzer can be connected to the three-phase stator winding and the housing respectively, wherein one end is connected to the three-phase stator winding, that is, connected to the three-phase short-circuit point, refer to Figure 3As shown, it is a wiring diagram of a common mode impedance test provided in an embodiment of the present application, where one end of the impedance analyzer is connected to the three-phase short-circuit point, and the other end is connected to the casing.

[0074] The measurement result is the curve of common mode impedance changing with frequency, that is, the first corresponding relationship, refer to Figure 4 As shown, it is a schematic diagram of a common-mode impedance curve provided in an embodiment of the present application, the horizontal axis is frequency, the vertical axis is impedance and phase angle, and the two curves represent the amplitude and phase angle of impedance respectively.

[0075] Specifically, the impedance amplitude and phase angle corresponding to different frequencies can be reflected from the first corresponding relationship, so that the port capacitance between the stator winding and the housing can be determined, and then the common mode inductance can be calculated based on the port capacitance and the first corresponding relationship. In short, measuring the common mode inductance in this way is simple and the result is accurate.

[0076] In a possible implementation, based on the first corresponding relationship, the port capacitance between the stator winding and the casing is determined. Specifically, the frequency and impedance corresponding to the phase angle of -90° are determined from the first corresponding relationship; and the port capacitance between the stator winding and the casing is calculated according to the frequency and impedance corresponding to the phase angle of -90°.

[0077] Specifically, when the common mode circuit is a pure capacitive characteristic, the calculated port capacitance will be more accurate. Therefore, the impedance and frequency corresponding to the phase angle of -90° are determined from the first corresponding relationship. At this time, it is a circuit with pure capacitive characteristics, that is, Figure 4 Point A in the figure, and the impedance corresponding to point A is recorded as Z A , the corresponding frequency is recorded as f A , then the terminal capacitance C between the stator winding and the housing wfp It can be expressed as:

[0078]

[0079] Then, based on the first corresponding relationship and the port capacitance, the common mode inductance can be determined. Specifically, point B is determined from the first corresponding relationship. The phase angle of the impedance at point B is -90°. At this time, the common mode inductance L of the motor is c With the port capacitance C wfp Series resonance occurs, which can be calculated based on the resonant frequency f at point B. B Calculate the common mode inductance L c :

[0080]

[0081] S104, performing differential mode impedance analysis on the motor to determine eddy current equivalent resistance.

[0082] Specifically, the motor is connected to an impedance analyzer to form a differential mode loop, so as to calculate the eddy current equivalent resistance. The eddy current equivalent resistance can be understood as the resistance corresponding to the parallel resonance of the differential mode port of the stator winding.

[0083] In one possible implementation, a differential mode impedance analysis is performed on the motor to determine the eddy current equivalent resistance. Specifically, the impedance between the two-phase stator winding and the third-phase stator winding is measured to obtain a second corresponding relationship between the differential mode impedance and the frequency; the impedance corresponding to the phase angle of 0° is determined from the second corresponding relationship; and the eddy current equivalent resistance is calculated based on the impedance corresponding to the phase angle of 0°.

[0084] Specifically, one end of the impedance analyzer can be connected to the two-phase short-circuit point, that is, connected to the two-phase stator winding, and the other end can be connected to the third-phase stator winding, so as to measure the impedance between the two-phase short-circuit point and the third-phase winding, and obtain a test curve of differential mode impedance versus frequency, which is the second corresponding relationship. As an example, refer to Figure 5 , which is a wiring diagram of a differential mode impedance test provided by an embodiment of the present application, wherein an impedance analyzer is connected to the housing of a motor. Figure 6 , which is a schematic diagram of a differential mode impedance curve provided in an embodiment of the present application.

[0085] Specifically, when the phase angle of the impedance is 0°, that is, Figure 6 Point C in the figure shows that the differential mode circuit exhibits pure resistance characteristics, and the differential mode resistance R e It is composed of three single-phase resistors R e1 Parallel, i.e. R e =R e1 / 3, and the differential impedance characteristic is equivalent to two phases in parallel and the third phase in series, so the impedance at point C can be expressed as Z c =3R e1 / 2. In this way, the impedance Z is determined from the second corresponding relationship. c Afterwards, R can be calculated e1 , and then get the differential mode resistance, differential mode resistance R e That is the eddy current equivalent resistance R e :

[0086]

[0087] In this way, a more accurate eddy current equivalent resistance can be calculated, and the calculation process is concise.

[0088] In a possible implementation, in the first correspondence and the second correspondence, the frequency range can be 10 3 -10 6Hz, this frequency band can be considered as a high frequency band, so that the EDM current can be extended to the high frequency band. The current conditions in the high frequency band are taken into consideration, which facilitates the calculation of more accurate shaft current and shaft voltage.

[0089] S105, calculating the impedance parameters in the circulating shaft current loop.

[0090] Specifically, the impedance parameters in the circulating shaft current loop can be obtained based on the number of stator laminations, vacuum magnetic permeability, relative magnetic permeability of stator laminations, inner and outer diameters of the stator, etc., using the cir_calculating program, which is a matlab m-code file. The circulating shaft current loop can be understood as a closed loop between the rotating shaft-drive end bearing-stator core / casing-non-drive end bearing-rotating shaft. The impedance parameters may include inductance, resistance, stator core path impedance, and rotor lamination path impedance. In other words, the inductance L in the circulating shaft current loop can be calculated. g , resistor R g , and the stator core path impedance Z bcir and rotor lamination path impedance Z rotor .

[0091] It is understandable that the order of calculating the motor stray capacitance, bearing equivalent capacitance, common mode inductance, eddy current equivalent capacitance and impedance parameters is not specifically limited here. For example, the impedance parameters can be calculated first, and then the motor stray capacitance can be calculated. Of course, they can also be calculated at the same time.

[0092] S106: Based on the motor stray capacitance, bearing equivalent capacitance, common mode inductance, eddy current equivalent resistance and impedance parameters, an electrical model is built to simulate the shaft current and shaft voltage at both ends of the bearing.

[0093] EDM current is mainly formed when the shaft voltage caused by electrostatic induction or variable frequency power supply is large enough to break through the bearing lubricating oil film. The circulating current can be understood as the parasitic capacitance between the stator winding and the housing under the action of the high-frequency common-mode voltage, which generates a high-frequency common-mode current flowing through the stator core. The common-mode current generates a high-frequency magnetic flux around the motor shaft, and then induces shaft voltage and shaft current along the shaft.

[0094] Specifically, the motor stray capacitance, bearing equivalent capacitance, common mode inductance, and eddy current equivalent resistance will affect the EDM current, and the impedance parameters will affect the circulating current in the circulating shaft current loop. Based on them, the corresponding electrical model can be built, for example, in Simulink simulation software, and the shaft current and shaft voltage at both ends of the bearing can be simulated. The shaft current is the current flowing through the bearing, and the shaft voltage is the shaft voltage at both ends of the bearing, that is, the voltage between the inner and outer rings of the bearing.

[0095] As an example, refer to Figure 7As shown, it is a structural schematic diagram of an electrical model provided in an embodiment of the present application, which includes three-phase input terminals u, v, and w. The dotted box parts are the corresponding parts of the two bearings, and the subscript numbers of each variable in the figure mean equal division.

[0096] In summary, in this application, by combining the transmission paths of the EDM current and the circulating current, the construction of an electrical model that comprehensively considers the EDM current and the circulating current is realized, so that the shaft current and shaft voltage of the bearing can be accurately and directly calculated. Different sources of shaft current are considered in this application, among which the motor stray capacitance, bearing equivalent capacitance, common mode inductance and eddy current equivalent resistance will affect the EDM current, and the impedance parameters will affect the circulating current. Building a simulation model based on them can achieve comprehensive consideration of the EDM current and the circulating current, making the calculated shaft current and shaft current more accurate, and more accurately evaluating the use of the motor bearings.

[0097] Based on the above shaft current and shaft voltage calculation method, the present application embodiment also provides a shaft current and shaft voltage calculation device, referring to Figure 8 As shown, it is a structural block diagram of a shaft current and shaft voltage calculation device provided in an embodiment of the present application, and the device may include:

[0098] The first calculation unit 201 is used to perform electrostatic field finite element calculation on the simulation model of the motor to obtain the stray capacitance of the motor;

[0099] A second calculation unit 202 is used to calculate the equivalent capacitance of the bearing based on the parameters of the bearing; the parameters of the bearing include the number of bearing balls, the diameter of the balls, the diameter of the inner ring of the bearing, the diameter of the outer ring of the bearing and the properties of the bearing material;

[0100] A first analysis unit 203, configured to perform common mode impedance analysis on the motor to determine common mode inductance;

[0101] A second analysis unit 204 is used to perform differential mode impedance analysis on the motor to determine eddy current equivalent resistance;

[0102] The third calculation unit 205 is used to calculate the impedance parameters in the circulating shaft current loop; the impedance parameters include inductance, resistance, stator core path impedance and rotor lamination path impedance;

[0103] The simulation unit 206 is used to build an electrical model based on the motor stray capacitance, the bearing equivalent capacitance, the common mode inductance, the eddy current equivalent resistance and the impedance parameter, and simulate the shaft current and shaft voltage at both ends of the bearing.

[0104] Specifically, the first computing unit is used to:

[0105] Based on the physical structure of the motor, construct the simulation model of the motor;

[0106] Setting voltage boundary conditions; the voltage boundary conditions include the voltage boundary of the stator winding, the voltage boundary of the stator core and the voltage boundary of the rotor;

[0107] Based on the voltage boundary condition, electrostatic field finite element calculation is performed on the simulation model to obtain the motor stray capacitance; the motor stray capacitance includes a first capacitance between the stator winding and the housing, a second capacitance between the stator winding and the rotor, and a third capacitance between the housing and the rotor.

[0108] Specifically, the simulation model is a single-slot simulation model, and the first computing unit is used to:

[0109] Performing electrostatic field finite element calculation on the single slot simulation model based on the voltage boundary condition to obtain the single slot stray capacitance;

[0110] The motor stray capacitance is determined based on the single-slot stray capacitance and the number of slots of the stator.

[0111] Specifically, the first analysis unit is used for:

[0112] Measuring the impedance between the three-phase stator winding and the housing to obtain a first corresponding relationship between the common mode impedance and the frequency;

[0113] Based on the first corresponding relationship, determining the port capacitance between the stator winding and the housing;

[0114] The common mode inductance is determined based on the first corresponding relationship and the port capacitance.

[0115] Specifically, the first analysis unit is used for:

[0116] Determine the frequency and impedance corresponding to the phase angle of -90° from the first corresponding relationship;

[0117] The port capacitance between the stator winding and the housing is calculated according to the frequency and impedance corresponding to the phase angle of -90°.

[0118] Specifically, the second analysis unit is used for:

[0119] Measuring the impedance between the two-phase stator winding and the third-phase stator winding to obtain a second corresponding relationship between the differential mode impedance and the frequency;

[0120] Determine the impedance corresponding to the phase angle of 0° from the second corresponding relationship;

[0121] The eddy current equivalent resistance is calculated according to the impedance corresponding to the phase angle of 0°.

[0122] Specifically, the frequency range is 10 3 -10 6 Hz.

[0123] In another aspect, the present application provides a computer device, referring to Fig. 9 , which is a structural diagram of a computer device provided in an embodiment of the present application, wherein the computer device includes a processor 310 and a memory 320:

[0124] The memory 320 is used to store program codes and transmit the program codes to the processor 310;

[0125] The processor 310 is used to execute the method provided in the above embodiment according to the instructions in the program code.

[0126] The computer device may include a terminal device or a server, and the aforementioned apparatus may be configured in the computer device.

[0127] On the other hand, an embodiment of the present application further provides a storage medium, wherein the storage medium is used to store a computer program, and the computer program is used to execute the method provided by the above embodiment.

[0128] A person skilled in the art can understand that all or part of the steps of implementing the above method embodiment can be completed by program instruction hardware, and the above program can be stored in a computer-readable storage medium. When the program is executed, it executes the steps of the above method embodiment; and the above storage medium can be at least one of the following media: read-only memory (English: Read-only Memory, abbreviated: ROM), RAM, magnetic disk or optical disk, etc. Various media that can store program codes.

[0129] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0130] The above is only a preferred implementation of the present application. Although the present application has been disclosed as a preferred embodiment, it is not intended to limit the present application. Any technician familiar with the art can use the above disclosed methods and technical contents to make many possible changes and modifications to the technical solution of the present application without departing from the scope of the technical solution of the present application, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present application without departing from the content of the technical solution of the present application still falls within the scope of protection of the technical solution of the present application.

Claims

1. A method for calculating shaft voltage and shaft current, characterized in that: include: Perform electrostatic field finite element calculation on the simulation model of the motor to obtain the stray capacitance of the motor; Calculating the equivalent capacitance of the bearing based on the parameters of the bearing; the parameters of the bearing include the number of bearing balls, the diameter of the balls, the diameter of the inner ring of the bearing, the diameter of the outer ring of the bearing and the properties of the bearing material; Performing common mode impedance analysis on the motor to determine common mode inductance; Performing differential mode impedance analysis on the motor to determine eddy current equivalent resistance; Calculating impedance parameters in the circulating shaft current loop; the impedance parameters include inductance, resistance, stator core path impedance and rotor lamination path impedance; Based on the motor stray capacitance, the bearing equivalent capacitance, the common mode inductance, the eddy current equivalent resistance and the impedance parameters, an electrical model is built to simulate the shaft current and shaft voltage at both ends of the bearing.

2. The method according to claim 1, characterized in that The electrostatic field finite element calculation is performed on the simulation model of the motor to obtain the stray capacitance of the motor, including: Based on the physical structure of the motor, construct the simulation model of the motor; Setting voltage boundary conditions; the voltage boundary conditions include the voltage boundary of the stator winding, the voltage boundary of the stator core and the voltage boundary of the rotor; Based on the voltage boundary condition, electrostatic field finite element calculation is performed on the simulation model to obtain the motor stray capacitance; the motor stray capacitance includes a first capacitance between the stator winding and the housing, a second capacitance between the stator winding and the rotor, and a third capacitance between the housing and the rotor.

3. The method according to claim 2, characterized in that The simulation model is a single-slot simulation model, and the electrostatic field finite element calculation is performed on the simulation model based on the voltage boundary condition to obtain the stray capacitance of the motor, including: Performing electrostatic field finite element calculation on the single slot simulation model based on the voltage boundary condition to obtain the single slot stray capacitance; The motor stray capacitance is determined based on the single-slot stray capacitance and the number of slots of the stator.

4. The method according to claim 1, characterized in that: The performing common mode impedance analysis on the motor to determine the common mode inductance includes: Measuring the impedance between the three-phase stator winding and the housing to obtain a first corresponding relationship between the common mode impedance and the frequency; Based on the first corresponding relationship, determining the port capacitance between the stator winding and the housing; The common mode inductance is determined based on the first corresponding relationship and the port capacitance.

5. The method according to claim 4, characterized in that The determining, based on the first corresponding relationship, the port capacitance between the stator winding and the housing includes: Determine the frequency and impedance corresponding to the phase angle of -90° from the first corresponding relationship; The port capacitance between the stator winding and the housing is calculated according to the frequency and impedance corresponding to the phase angle of -90°.

6. The method according to claim 1, characterized in that The step of performing differential mode impedance analysis on the motor to determine eddy current equivalent resistance includes: Measuring the impedance between the two-phase stator winding and the third-phase stator winding to obtain a second corresponding relationship between the differential mode impedance and the frequency; Determine the impedance corresponding to the phase angle of 0° from the second corresponding relationship; The eddy current equivalent resistance is calculated according to the impedance corresponding to the phase angle of 0°.

7. The method according to claim 4 or 6, characterized in that: The frequency range is 10 3 -10 6 Hz.

8. A device for calculating shaft voltage and shaft current, characterized in that: include: A first calculation unit is used to perform electrostatic field finite element calculation on the simulation model of the motor to obtain the stray capacitance of the motor; A second calculation unit is used to calculate the equivalent capacitance of the bearing based on the parameters of the bearing; the parameters of the bearing include the number of bearing balls, the diameter of the balls, the diameter of the inner ring of the bearing, the diameter of the outer ring of the bearing and the properties of the bearing material; A first analysis unit, configured to perform common mode impedance analysis on the motor to determine common mode inductance; A second analysis unit is used to perform differential mode impedance analysis on the motor to determine eddy current equivalent resistance; A third calculation unit is used to calculate impedance parameters in the circulating shaft current loop; the impedance parameters include inductance, resistance, stator core path impedance and rotor lamination path impedance; The simulation unit is used to build an electrical model based on the motor stray capacitance, the bearing equivalent capacitance, the common mode inductance, the eddy current equivalent resistance and the impedance parameter, and simulate the shaft current and shaft voltage at both ends of the bearing.

9. A computer device, characterized in that: The computer device comprises a processor and a memory: The memory is used to store program code and transmit the program code to the processor; The processor is configured to execute the method according to any one of claims 1 to 7 according to the instructions in the program code.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium is used to store a computer program, and the computer program is used to execute the method according to any one of claims 1 to 7.

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