A method for eccentric fault diagnosis of permanent magnet motor based on port voltage envelope

Abstract

This invention discloses a method for diagnosing eccentricity faults in permanent magnet motors based on port voltage envelopes, relating to the field of motor fault diagnosis technology. The method includes: firstly, winding i ≥ 3 detection coils on stator teeth of the permanent magnet motor with an integer number of pole pairs separated; secondly, simultaneously acquiring the voltage signals u of the i detection coils during stable operation of the permanent magnet motor. i (x); then, according to u i (x) Calculate the static eccentricity fault index SE and the dynamic eccentricity fault index DE; compare the fault characteristic value with the set threshold to determine the eccentricity fault type of the permanent magnet motor; realize the motor eccentricity fault diagnosis, and can effectively identify the static eccentricity, dynamic eccentricity and mixed eccentricity faults of the permanent magnet motor; the method is easy to implement and has low cost.

Description

Technical Field

[0001] This invention relates to the field of motor fault diagnosis technology, specifically a method for diagnosing eccentricity faults in permanent magnet motors based on the port voltage envelope. Background Technology

[0002] Permanent magnet motors, characterized by high speed, high torque, and high reliability, are widely used in aerospace, defense, automotive, and wind power industries. As devices that convert mechanical energy into electrical energy, ensuring their stable and efficient operation is crucial. Due to processing, assembly, and prolonged high-load operation, permanent magnet motors may experience various faults, with eccentricity being a common one. If eccentricity is not detected in time, prolonged eccentric operation generates unbalanced magnetic pull within the motor, causing bearing wear, further exacerbating the fault, and even leading to rotor damage. Research shows that after an eccentricity fault occurs in a permanent magnet motor, the uneven distribution of the air gap inside the motor leads to changes in the internal magnetic field distribution.

[0003] Therefore, by placing a detection coil inside the motor, and according to Faraday's law of electromagnetic induction, the induced voltage generated in the detection coil at different positions of the non-uniformly distributed magnetic field will vary. By monitoring the changes in the voltage at the port of the detection coil, the changes in the air gap inside the motor can be determined, thus enabling the diagnosis of motor eccentricity faults. To this end, this invention proposes a method for diagnosing eccentricity faults in permanent magnet motors based on the port voltage envelope. Summary of the Invention

[0004] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a method for diagnosing eccentricity faults in permanent magnet motors based on port voltage envelopes. This method realizes the diagnosis and type identification of eccentricity faults in permanent magnet motors, and can effectively identify static eccentricity, dynamic eccentricity, and mixed eccentricity faults in permanent magnet motors. This method is easy to implement and has low cost.

[0005] To achieve the above objectives, according to an embodiment of the first aspect of the present invention, a method for diagnosing eccentricity faults in permanent magnet motors based on port voltage envelopes is proposed, comprising the following steps:

[0006] Step 1: Use enameled wire to wind three detection coils onto the teeth of the permanent magnet stator to be diagnosed; wherein each detection coil is spaced an integer number of pole pairs apart;

[0007] Step 2: When the motor is running smoothly, the voltage signal u at each probe coil port is acquired through the voltage sampling circuit. i (x);

[0008] Step 3: Calculate the static eccentricity fault index SE and the dynamic eccentricity fault index DE based on the voltage signal;

[0009] Step 4: Compare the static eccentricity index SE and the dynamic eccentricity index DE with the set threshold T. se and T de Compare and determine whether the motor has static or dynamic eccentricity faults.

[0010] Furthermore, the specific calculation steps for the static eccentricity fault index SE and the dynamic eccentricity fault index DE are as follows:

[0011] S31: First, take the absolute value of the three sets of probe coil voltage signals obtained; that is:

[0012] U (i) (x)=|u sc(i) (x)| (1)

[0013] S32: Take the upper envelope of the obtained absolute value signal, that is:

[0014] U up(i) (x)=up(U (i) (x)) (2)

[0015] S33: To U up(i) (x) take the reciprocal, that is:

[0016]

[0017] S34: Normalize the three sets of signals using the signal mean, i.e.

[0018]

[0019]

[0020] S35: For the normalized signal, three sets of signals W N(i) (x) Take the upper envelope and lower envelope respectively, that is:

[0021] V up(i) (x)=up(W N(i) (x)) (6)

[0022] V low(i) (x)=low(W N(i) (x)) (7)

[0023] S36: Calculate the mean of the upper and lower envelopes for each group, i.e.:

[0024]

[0025] S37: Take the variance of the mean of the upper and lower envelopes of each signal group as the static eccentricity existence index, that is:

[0026] SE = S(V) (i)(9)

[0027] S38: Take the average distance between the upper and lower envelopes of the three sets of signals as the dynamic eccentricity existence index, that is:

[0028]

[0029] Furthermore, in step four, determining the static and dynamic eccentricity faults of the motor specifically involves:

[0030] If SE≥T se Then there exists static eccentricity; if DE≥T de Then there is dynamic eccentricity; if SE≥T se and DE≥T de If both conditions are met, then the motor will exhibit mixed eccentricity.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] This invention places a detection coil inside the motor. According to Faraday's law of electromagnetic induction, the induced voltage generated in the detection coil at different positions of the non-uniformly distributed magnetic field is different. By monitoring the voltage change at the port of the detection coil, the change of the air gap inside the motor can be known, thus realizing the diagnosis of motor eccentricity faults. It can effectively identify static eccentricity, dynamic eccentricity and mixed eccentricity faults of permanent magnet motors. This method is easy to implement and has low cost. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram showing the placement of the detection coils in this invention.

[0035] Figure 2 This is a schematic diagram of the principle of the present invention. Detailed Implementation

[0036] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] in Figure 1The model shows a 36-slot 8-pole permanent magnet motor and the specific placement of the detection coils within the slots. Each detection coil is spaced an integer number of pole pairs apart. The detection coils are placed within the stator slots and are embedded directly at the factory. After the motor is successfully manufactured, the detection coils are inserted into the slot openings, and then slot wedges are inserted to seal the openings.

[0038] like Figure 2 As shown, a method for diagnosing eccentricity faults in a permanent magnet motor based on the port voltage envelope includes the following steps:

[0039] Step 1: Use enameled wire to wind three detection coils onto the teeth of the permanent magnet stator to be diagnosed; wherein each detection coil is spaced an integer number of pole pairs apart;

[0040] Step 2: When the motor is running smoothly, the voltage signal u at each probe coil port is acquired through the voltage sampling circuit. i (x);

[0041] Step 3: Calculate the static eccentricity fault index SE and the dynamic eccentricity fault index DE based on the voltage signal; the specific calculation steps are as follows:

[0042] S31: First, take the absolute value of the three sets of probe coil voltage signals obtained; that is:

[0043] U (i) (x)=|u sc(i) (x)| (1)

[0044] S32: Take the upper envelope of the obtained absolute value signal, that is:

[0045] U up(i) (x)=up(U (i) (x)) (2)

[0046] S33: To U up(i) (x) take the reciprocal, that is:

[0047]

[0048] S34: Normalize the three sets of signals using the signal mean, i.e.

[0049]

[0050]

[0051] S35: For the normalized signal, three sets of signals W N(i) (x) Take the upper envelope and lower envelope respectively, that is:

[0052] V up(i) (x)=up(W N(i)(x)) (6)

[0053] V low(i) (x)=low(W N(i) (x)) (7)

[0054] S36: Calculate the mean of the upper and lower envelopes for each group, i.e.:

[0055]

[0056] S37: Take the variance of the mean values ​​of the upper and lower envelopes of each signal group as an index of static eccentricity existence.

[0057] SE = S(V) (i) (9)

[0058] S38: Take the average distance between the upper and lower envelopes of the three sets of signals as an indicator of dynamic eccentricity.

[0059]

[0060] Step 4: Compare the static eccentricity index SE and the dynamic eccentricity index DE with the set threshold T. se and T de Compare and determine the static and dynamic eccentricity faults of the motor, specifically:

[0061] If SE≥T se Then there exists static eccentricity; if DE≥T de Then there is dynamic eccentricity; if SE≥T se and DE≥T de If both conditions are met, then the motor will exhibit mixed eccentricity.

[0062] In this embodiment, the principle of the detection coil is as follows:

[0063] The length of the air gap at any angle under eccentric fault is

[0064]

[0065] According to Ohm's law for equivalent magnetic circuits, the magnetic flux of the j-th equivalent magnetic circuit is...

[0066]

[0067] Based on the above analysis, it can be seen that when an eccentric fault occurs in the motor, the magnetic flux in the equivalent magnetic circuit changes. To detect this change in magnetic flux, this paper proposes a method of tightly winding three detection coils on the stator teeth of the motor for eccentricity detection. Each detection coil is spaced an integer number of poles apart. The magnetic flux through the detection coils can be approximated as the magnetic flux of the equivalent magnetic circuit where that tooth is located. According to the law of electromagnetic induction, the voltage across the detection coil is:

[0068]

[0069] Pick These time points can be approximated as the time when the detection coil on the j-th stator tooth achieves its maximum electromotive force. Therefore, there will be p such time points within one mechanical cycle T.

[0070]

[0071]

[0072]

[0073] According to the theory of unit motors, a motor with Z stator slots and p pole pairs can be considered as consisting of p identical unit motors. When an eccentric fault occurs in the motor, it can be considered as p identical unit motors with different air gap distributions, and the winding magnetomotive force and magnetic reluctance R are different. c Since the distribution is exactly the same, the detection coils are installed on stator teeth spaced an integer number of pole pairs apart, which is equivalent to each detection coil being installed at the same position in different unit motors; that is:

[0074] R c(j(1)) =R c(j(2)) =R c(j(3)) =...=R c(j(p))

[0075]

[0076] To more easily calculate the degree of failure, for U max (j,k) and U min Take the reciprocal of (j,k) and define it as the fault indication quantity.

[0077] When the motor is fault-free

[0078]

[0079]

[0080] definition get

[0081] Conclusion: Based on the analysis, when the rotational speed is constant, W max (i,k) and W min (i,k) are DC quantities, and their absolute values ​​are equal;

[0082] When the motor only has static eccentricity

[0083]

[0084]

[0085] When the motor only has dynamic eccentricity

[0086]

[0087]

[0088] Conclusion: During dynamic eccentricity, the fault indication quantity W of the three detection coils max (i,k) and W min (i,k) can be regarded as the superposition of DC and cosine quantities. The DC component has the same amplitude, and the period of the cosine component is the mechanical period T. The time difference is 2π·i / p, the amplitude is equal, and the amplitude can reflect the degree of dynamic eccentricity.

[0089] When the motor is in a mixed eccentric state

[0090]

[0091]

[0092] Conclusion: Fault indication quantity W under mixed eccentricity state max (i,k) and W min (i,k) is equivalent to the linear superposition of static eccentricity and dynamic eccentricity. Static eccentricity causes the DC component amplitudes of the three fault indication quantities to be different, while dynamic eccentricity generates cosine components.

[0093] The diagnostic results for motors with different eccentric faults are shown in Table 1:

[0094] Static eccentricity Dynamic eccentricity SE DE Diagnostic results 0 0 <![CDATA[7.55*10 -4 ]]> <![CDATA[1.07*10 -2 ]]> healthy 18％ 0 <![CDATA[2.56*10 -2 ]]> <![CDATA[2.20*10 -3 ]]> Static eccentricity 27％ 0 <![CDATA[4.11*10 -2 ]]> <![CDATA[2.30*10 -3 ]]> Static eccentricity 36％ 0 <![CDATA[6.30*10 -2 ]]> <![CDATA[2.40*10 -3 ]]> Static eccentricity 45％ 0 <![CDATA[8.86*10 -2 ]]> <![CDATA[2.30*10 -3 ]]> Static eccentricity 54％ 0 <![CDATA[1.06*10 -1 ]]> <![CDATA[6.20*10 -3 ]]> Static eccentricity 63％ 0 <![CDATA[1.07*10 -1 ]]> <![CDATA[8.80*10 -3 ]]> Static eccentricity 0 36％ <![CDATA[4.90*10 -3 ]]> <![CDATA[3.03*10 -1 ]]> Dynamic eccentricity 0 45％ <![CDATA[6.10*10 -3 ]]> <![CDATA[3.67*10 -1 ]]> Dynamic eccentricity 0 54％ <![CDATA[8.30*10 -3 ]]> <![CDATA[4.37*10 -1 ]]> Dynamic eccentricity 0 63％ <![CDATA[1.00*10 -2 ]]> <![CDATA[4.90*10 -1 ]]> Dynamic eccentricity 18％ 18％ <![CDATA[3.19*10 -2 ]]> <![CDATA[1.58*10 -1 ]]> Mixed eccentricity 27％ 27％ <![CDATA[4.86*10 -2 ]]> <![CDATA[2.37*10 -1 ]]> Mixed eccentricity 36％ 18％ <![CDATA[3.65*10 -2 ]]> <![CDATA[3.01*10 -1 ]]> Mixed eccentricity 36％ 36％ <![CDATA[6.55*10 -2 ]]> <![CDATA[3.07*10 -1 ]]> Mixed eccentricity

[0095] Table 1

[0096] The above formulas are all numerical calculations after removing dimensions. The formulas are obtained by software simulation based on a large amount of data and are closest to the real situation. The preset parameters and preset thresholds in the formulas are set by those skilled in the art according to the actual situation or obtained by simulation based on a large amount of data.

[0097] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0098] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to any specific implementation. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1.A method for diagnosing eccentricity fault of a permanent magnet motor based on port voltage envelope, characterized in that, Comprising the following steps: Step one: three detection coils are wound on the stator teeth of the permanent magnet motor to be diagnosed by using enameled wire; wherein each detection coil is separated by an integer number of poles; Step two: when the motor runs smoothly, collect each detection coil port voltage signal through the voltage sampling circuit ; Step three: the static eccentricity fault index SE and the dynamic eccentricity fault index DE are calculated according to the voltage signals; Wherein, the specific calculation steps of the static eccentricity fault index SE and the dynamic eccentricity fault index DE are as follows: Step four: compare the static eccentricity index SE and the dynamic eccentricity index DE with the set threshold value and ; determine the motor static eccentricity and dynamic eccentricity faults; S31: first, take the absolute value of the three groups of detection coil voltage signals; that is: S32: take the upper envelope of the obtained absolute value signal, that is: （1） S34: normalize the three groups of signals by using the signal mean value, that is: （2） S33: To Take the reciprocal, i.e.: （3） S36: calculate the mean value of each group of upper and lower envelope lines, that is: （4） （5） S35: normalizing the three sets of signals The upper envelope and the lower envelope are taken separately, i.e. （6） （7） S37: take the variance of the mean value of each group of upper and lower envelope lines as the static eccentricity existence index, that is: （8） S38: take the mean value of the distance between the three groups of upper and lower envelope lines as the dynamic eccentricity existence index, that is: （9） Wherein, （10）。 2. The eccentric fault diagnosis method for permanent magnet motor based on port voltage envelope according to claim 1, characterized in that, The specific steps for judging the static eccentricity and dynamic eccentricity faults of the motor in step four are as follows: ​ If , there is static eccentricity; if , there is dynamic eccentricity; if and are both true, the motor has mixed eccentricity.

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