CN110501640A - A method for detecting static eccentricity of permanent magnet motors based on air gap magnetic field direct test - Google Patents

Abstract

A method for directly testing and detecting static eccentricity of permanent magnet motors based on an air-gap magnetic field, involving a detection method for motor faults, the steps are as follows: test the air-gap radial magnetic density of a standard motor under no eccentricity and different static eccentricity rates, and obtain static eccentricity rate and characteristic order Linear relationship between magnitudes The coefficient A in , where y is the static eccentricity and x is the characteristic order Amplitude; Test the air gap radial magnetic density of the circumferential spatial distribution of the motor to be tested; Drawing: Br ‑ standard and graph: Br ‑ test, subtracting Br ‑ standard from Br ‑test to obtain the magnetic density difference data, drawing Draw the magnetic density difference diagram; combine the Br -standard, Br -test and magnetic density difference diagram to determine the eccentric direction; analyze the spatial order characteristics of the Br -test, find its amplitude, and substitute it into , to get the static eccentricity y. The method of the invention is simple and convenient to use, and can accurately measure the static eccentric fault of the permanent magnet motor.

Description

A method for detecting static eccentricity of permanent magnet motors based on air gap magnetic field direct test

technical field

The invention relates to a detection method for a motor fault, more specifically a method for directly testing and detecting the static eccentricity of a permanent magnet motor based on an air gap magnetic field.

Background technique

The permanent magnet motor cancels the excitation system, so the structure is simple and the operation is reliable. The excitation winding loss is reduced and the efficiency is improved. From the national economy, industrial production, to automobiles, aerospace, national defense, etc., it has gradually been widely used in various industries. But at the same time, the permanent magnet motor will inevitably have eccentricity problems during operation. This kind of problem may come from: 1) Due to unqualified production and processing technology, the axis of the motor stator and rotor does not coincide; 2) Due to the wear and tear of the motor due to complex load conditions, harsh use environment, and continuous work, etc., resulting in Eccentricity occurs between the stator and rotor of the motor. Static eccentricity means that the rotation center of the rotor of the motor deviates from the rotation center of the stator, thereby distorting the air gap magnetic field. According to engineering experience and scientific research, static eccentricity will increase the vibration and noise of the motor and reduce the electromagnetic performance of the motor. In severe cases, it may cause direct contact between the stator and rotor of the motor, resulting in serious production accidents. Therefore, in the stage of motor production design and daily use, accurately detecting whether the motor has static eccentricity and determining the degree of static eccentricity can reduce the risk of failure and improve economic benefits, and has extremely high engineering value. After a comprehensive survey of existing literature, it is found that the existing motor eccentricity detection technology can be roughly divided into the following two categories:

One class of methods can determine the eccentricity direction:

1) Based on the indirect test of the air gap magnetic field to judge the eccentricity fault. Install detection coils or encoders in the stator slot or the inner surface of the stator, and detect the direction and degree of eccentricity by analyzing the voltage changes of the coils or encoders. However, it has the following disadvantages: the amplitude of the magnetic field induced by the coil is small, and the sensitivity is low; the motor needs to be greatly modified; the coil is prone to friction with the rotor at high speed; Determine the approximate direction of eccentricity.

2) Based on the zero-sequence back electromotive force of the three-phase asynchronous motor, the direction of the static eccentricity is judged by the fault indication vector of the static eccentricity. This method is not suitable for permanent magnet motors.

One class of methods cannot determine the direction of eccentricity:

1) Based on the stator current and its side frequency characteristics, the eccentricity fault is judged. Such methods are highly susceptible to load conditions and motor control methods, and the eccentric characteristic spectrum of the stator current may come from other fault factors. Furthermore, low-level eccentricity failures cannot be predicted because eccentricity spectral features tend to be small;

2) Calculate the static eccentricity based on the vibration response of the motor. The testing process of this kind of method is complicated, the testing cost is high, and it is susceptible to external interference.

Based on the existing literature, it can be found that the existing technologies are mostly aimed at AC induction motors, and the static eccentricity detection methods involving permanent magnet motors are rarely introduced. In addition, most of the existing technologies cannot determine the static eccentric direction, and the methods that can determine the eccentric direction are limited by the number of detection coils and cannot achieve high-precision positioning. Therefore, it is difficult to use the existing technology to achieve low cost, high precision, easy operation and suitable for detecting the direction and degree of static eccentricity of permanent magnet motors.

Contents of the invention

The purpose of the present invention is to solve the shortcomings of the above-mentioned prior art, such as insufficient test accuracy, large test error, complicated modification process, complicated test process, and inability to accurately locate the eccentric direction, and provide a method that is simple, easy to use, and can accurately measure A detection method for static eccentric faults of permanent magnet motors.

The technical solution adopted by the present invention to solve the above-mentioned deficiencies in the prior art is:

A method for directly testing and detecting the static eccentricity of a permanent magnet motor based on an air-gap magnetic field, characterized in that it comprises the following steps:

Step 1: Test the air-gap radial flux density of the standard motor under no eccentricity and different static eccentricities, and obtain the static eccentricity and characteristic order Linear relationship between magnitudes The coefficient A in , where y is the static eccentricity and x is the characteristic order the amplitude of

Step 2: Test the radial magnetic density of the air gap distributed in the circumferential space of the motor to be tested;

Step 3. According to the test data of air gap radial flux density obtained in step 1 and step 2, draw the radial flux density spatial distribution diagram of the standard motor without eccentricity: Br - the radial flux density spatial distribution of the standard and the motor to be tested Figure: Br -test, then subtract the Br -standard curve data from the curve data in the Br -test to obtain the magnetic density difference data, and draw the magnetic density difference diagram according to the magnetic density difference data;

Step 4. Combining the radial magnetic density spatial distribution diagram of the standard motor without eccentricity, the radial magnetic density spatial distribution diagram and the magnetic density difference diagram of the motor to be tested, determine the eccentricity direction;

Step 5. Analyze the spatial order characteristics of the Br -test, find the magnitude of the static eccentric feature space order, and substitute it into the linear relationship , the static eccentricity y can be obtained.

In the step 1, the following steps are specifically included:

11): Set the test condition point of the motor under test, as shown in Figure 3. Take the circle at the center of the air gap (radial direction) of the motor, (establish a coordinate system,) divide it into N parts, and use the angle is the interval, where p is the number of pole pairs of the motor, (the measuring point in the X-axis direction is the starting point of the test,) each motor air gap (center) is a test point;

12): Install and fix the motor under test on the rotary table, control the probe bracket so that the Tesla meter enters the test starting point in the air gap of the permanent magnet motor, test the radial magnetic density at this point and record it;

13): Control the rotary table, rotate the motor under test to the next test point in the circumferential direction, test the radial magnetic density at this point and record; repeat the test until each test point (circumferential spatial distribution ) of the radial flux density are all measured.

14) Set the eccentricity of the standard motor at equal intervals, the interval is not less than 10% of the static eccentricity, and the total number is not less than 8 groups; different static eccentricities can be obtained by plugging brass feeler gauges of different thicknesses on the side of the air gap Rate , e is the static eccentricity, δ is the original length of the air gap;

15) Repeat steps 11), 12) and 13) to test the radial flux density spatial distribution of the standard motor at each static eccentricity;

16) Perform spatial order analysis on the radial magnetic density of standard motors at various static eccentricities to obtain the amplitude of the characteristic order;

17) Take the static eccentricity as the dependent variable, and the characteristic order magnitude under each eccentricity as the independent variable, and obtain the linear relationship between the two A in .

The test method of the radial magnetic density of the air gap distributed in the circumferential space of the motor to be tested is the same as the test method of the radial magnetic density of the air gap distributed in the circumferential space of the motor under test in step 1.

In the described step 4, the following steps are specifically included:

41) Find the two symmetrical zero point positions of the magnetic density difference diagram, as shown in Figure 6, and calculate the angle values of the two midpoints (the side of the superior arc and the side of the inferior arc), and then the air gap after eccentricity can be obtained Maximum position (negative direction of eccentricity) and minimum position of air gap (direction of eccentricity).

42) The angle interval of the eccentric direction can be determined by the amplitude change of the motor to be tested relative to the standard motor without eccentricity, as shown in Figure 5, the central angle at the zero point within the angular interval of the eccentric direction is the eccentric direction.

Described step 4, its technical basis is, as shown in Figure 4:

When static eccentricity occurs, the rotor rotation center O _r shifts and does not coincide with the stator center O _s . The length of the air gap changes within the entire circumference range. There must be two points symmetrically distributed on both sides of the eccentric direction within the range of the circumference. The radial flux density will not change either. The center position of the two points is the position of the maximum air gap (the side of the inferior arc) or the position of the minimum air gap (the side of the superior arc), combined with the circumferential spatial distribution diagram of the radial flux density tested, as shown in Figure 5, The direction of eccentricity can be determined.

The technical feature on which the present invention is based is: when statically eccentric, as shown in Figure 4, the length of the air gap changes within the entire circumference, and the minimum position of the air gap is fixed. The magnetic permeability of the air gap is close to the vacuum magnetic permeability, and its value is much smaller than the magnetic permeability of the stator magnetic material. The larger the air gap width, the larger the reluctance and the smaller the corresponding magnetic density amplitude. With this The characteristic can be used to locate the direction of static eccentricity; and as the degree of static eccentricity increases, the greater the change in the width of the air gap, the higher the amplitude of the characteristic frequency. After calculation, there is a linear relationship between the characteristic frequency amplitude and the static eccentricity, and by virtue of this feature, the degree of static eccentricity can be determined.

The invention is based on the direct test of the air gap magnetic field of the permanent magnet motor. The air-gap magnetic field is the basis for permanent magnet motors to realize electromechanical energy conversion, and static eccentricity will significantly affect the flux density waveform of permanent magnet motors, causing the amplitude of the waveform to change in the eccentric direction. The position of the changing value directly corresponds to the direction of eccentricity, and the changing value has a linear relationship with the degree of eccentricity. Therefore, it is possible to quickly and accurately detect whether there is static eccentricity in the motor and determine the direction and degree of static eccentricity.

By using the method for detecting the static eccentricity fault of the hub motor of the present invention, it is possible to accurately determine whether there is static eccentricity in the permanent magnet motor and accurately determine the direction and degree of the static eccentricity. The invention has the advantages of simple operation, high detection precision, accurate detection of eccentric direction and the like.

Compared with the prior art, the beneficial effects of the present invention are reflected in:

1. The invention can be widely applied to various permanent magnet motors to realize the static eccentricity detection of the permanent magnet motors.

2. The invention can simultaneously realize high-precision static eccentricity direction detection and eccentricity degree detection.

3. The evaluation index based on the present invention has been scientifically demonstrated by analytical formulas and finite element simulation tools, and is less affected by other non-eccentric fault factors, so it has high precision.

Description of drawings

Figure 1 is a detection flow chart.

Fig. 2 is a schematic diagram of the structure of the air-gap magnetic field direct test device.

Figure 3 is a schematic diagram of the setting of measuring points for air gap magnetic field direct testing.

Figure 4 is a schematic diagram of the static eccentricity of the motor.

Figure 5 is the spatial distribution diagram of the air gap radial magnetic field in two static eccentric directions (135° and 270°).

Figure 6 is a diagram of the difference in radial magnetic density between the motor under test and the standard motor in two static eccentric directions (135° and 270°).

Fig. 7 is a linear relationship between the static eccentricity and the magnitude of the characteristic order in the embodiment.

Fig. 8 is a spatial distribution diagram of the radial magnetic field of the motor to be tested and the standard motor in the embodiment.

Fig. 9 is a difference diagram of the radial flux density between the motor under test and the standard motor in the embodiment.

Fig. 10 is a spatial order diagram of the motor to be tested in the embodiment.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

For a 24-pole 27-slot electric vehicle with an outer rotor hub permanent magnet synchronous motor, the whole process of static eccentricity detection is carried out according to the method of the present invention.

As shown in Figure 1, it is a schematic diagram of the structure of the air gap magnetic field direct test device, which is provided with a test platform 1, a vertical adjustment bracket 5 and an adjustment screw 3; a horizontal adjustment bracket 4 and a horizontal adjustment screw 6; Tesla probe 8, probe 7 And the data acquisition host 11; the rotary table 10 and the index plate 2; the motor 9 under test.

For the motor to be tested, as shown in the flow chart in Figure 4, there is the following execution process:

1) Test the air-gap radial magnetic field of the standard motor under no eccentricity and different static eccentricity, and obtain the static eccentricity and characteristic order Linear relationship between magnitudes , as shown in Figure 7.

2) Test the radial magnetic field of the air gap distributed in the circumferential space of the motor to be tested.

3) According to the test data of the radial magnetic field obtained in step 1 and step 2, draw the spatial distribution diagram of the radial magnetic field: Br - test and Br - standard, as shown in Figure 8; then subtract Br - from the curve data in the Br - test The standard curve data is used to obtain the magnetic density difference data, and the magnetic density difference diagram is drawn, as shown in Figure 9.

4) Combining the magnetic density spatial distribution diagram and the magnetic density difference diagram, determine the eccentric direction:

41) From the zero position in Figure 9, determine the central angles as 224.83° and 44.83°.

42) From Figure 8, it is judged that the maximum radial magnetic density of the air gap, that is, the angle range of the eccentric direction is between 180°-270°. Based on Fig. 8 and Fig. 9, the center angle of the zero position located in the angle range of the eccentric direction is the eccentric direction, and it can be judged that the eccentric direction is 224.83°.

5) Analyze the spatial order characteristics of the Br -test to find the amplitude of the static eccentricity characteristic space order, as shown in Figure 10, the obtained characteristic order amplitude is 0.09519T; substituting the linear relational formula, the static eccentricity degree can be obtained: Substituting into the relationship obtained in 2), as shown in Figure 7, the static eccentricity can be obtained as 90%.

Compared with the prior art, the invention can quickly, easily and accurately detect whether there is static eccentricity in the permanent magnet motor and determine the accurate eccentricity direction and eccentricity degree.

Claims (3)

1. a kind of directly test the static eccentric method of detection magneto based on air-gap field, it is characterised in that including walking as follows It is rapid:

Step 1: testing the air gap radial direction flux density of standard electromotor under lower and different static eccentricities without acceptance of persons, obtain static bias Rate and feature orderLinear relationship between amplitudeIn coefficientA,WhereinyFor static eccentricity,xIt is characterized OrderAmplitude；

Step 2: air gap radial direction flux density of the test to measured motor circumferential direction spatial distribution；

Diameter of the step 3. according to the test data of step 1 and step 2 gained air gap radial direction flux density, under drawing standard electromotor without acceptance of persons To flux density spatial distribution map:BrStandard and radial flux density spatial distribution map to measured motor:Br-Test, is then usedBrTest In curve data subtractBrThe curve data of standard obtains flux density difference data, and it is poor to draw flux density according to flux density difference data Value figure；

Step 4. combined standard motor without acceptance of persons under radial flux density spatial distribution map, the radial flux density space point to measured motor Butut and flux density differential chart, determine eccentric direction；

Step 5. is rightBrTest carries out space order specificity analysis, finds the amplitude of static eccentric nature space order, substitutes into Linear relation, static eccentricity y can be obtained.

2. according to claim 1 directly test the static eccentric method of detection magneto, spy based on air-gap field It levies and is in the step 1, comprising the following steps:

11): the measurement condition point of tested motor being set: taking the circle at the center of motor gas-gap, is divided intoNPart, with angleTo be spaced, whereinpIt is a measurement condition point at every part of motor gas-gap for the number of pole-pairs of motor；

12): fixed tested motor being installed on rotary table, the test starting for entering Tesla meter in magneto air gap At operating point, tests radial direction flux density at this and record；

13): control rotary table rotates at next measurement condition point in tested motor to its circumferential direction, tests radial at this Flux density simultaneously records；Retest finishes until the radial flux density of each measurement condition point all measures；

14) eccentricity of established standards motor, interval are not less than 10% static eccentricity at equal intervals, and sum is no less than 8 groups；

And 13) 15) step 11), 12) is repeated, the radial flux density spatial distribution of standard electromotor under each static eccentricity is tested；

16) space order analysis is carried out to the radial flux density of standard electromotor under each eccentricity, obtains the amplitude of feature order；

17) using static eccentricity as dependent variable, the feature order amplitude under each eccentricity is independent variable, seeks line between the two Sexual intercourse formulaInA。

3. according to claim 1 directly test the static eccentric method of detection magneto, spy based on air-gap field It levies and is in the step 4, comprising the following steps:

41) two symmetrical dead-center positions of flux density differential chart are found, and calculate the angle value at two midpoint, bias can be obtained Air gap maximum position and air gap minimum position afterwards；

42) by measured motor, the amplitude variation of standard electromotor can determine the angular interval of eccentric direction without acceptance of persons relatively, then it is located at The centric angle of dead-center position is eccentric direction in eccentric direction angular interval.