RU2572791C2 - Method to assess quality of soldered joint in windings of electric machines - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: invention relates to investigation or analysis of materials using vortex currents and may be used to monitor quality of soldered joints in windings of various electric machines (EM) during production and repair. The method to assess quality of a soldered joint of windings of electric machines consists in the fact that the joint is probed with a vortex current meter, for which purpose the excitation winding located at one side of the joint is used to develop a magnetic field, which is received by the coaxial measurement winding located at the opposite side of the joint. Received signal amplitude is measured. Prior to measurements the meter is calibrated, for which purpose they probe reference joints: non-soldered, fully soldered, and then the investigated joint. The quality of the investigated soldered joint of the electric machine winding is assessed, comparing amplitudes of the received signal with signals from reference joints. During probing of joints they additionally measure the phase of the received signal, during calibration they probe the non-soldered and fully soldered joints several times under various relative positions of the joint and windings of the meter. They calculate the position of the equidistant point of the complex plane, relative to which the amplitude of received signals does not depend on the relative position of the joint and windings both for non-soldered and soldered joints. To assess the degree of joint soldering they use ratios of amplitudes of received signals of reference and investigated joints, recalculated relative to the equidistant point.

EFFECT: increased accuracy of measurements; at the same time the process of measurements becomes invariant to accuracy of setting of windings and their dimensions relative to a soldered joint.

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Description

The invention relates to the study or analysis of materials using eddy currents and can be used to control the quality of soldered connections of the windings of various electrical machines (EM): hydro and turbogenerators, synchronous and asynchronous high-power motors, etc. during production and repair.

As an example of an EM, we consider the stator winding of a turbogenerator, which is a set of isolated copper conductors insulated from each other, laid in the slots of the active part of the turbogenerator. The connection of the conductors of the stator winding rods is made in the frontal parts of the turbogenerator [1], FIG. 1. All conductors are clamped together and soldered together. Pairs of clamps, in turn, are soldered in a fork. A load current of a turbogenerator phase with a force of the order of several kA flows through the stator winding.

Power losses in the event of defects in the soldered joints of the stator windings of turbogenerators can reach tens of kW. Poor soldering can cause local overheating and failure of connections. This makes it necessary to conduct non-destructive testing of soldered joints during the manufacture and routine maintenance of EMs.

Known [2] is a method of controlling the quality of soldering current-carrying EM connections, which consists in measuring the voltage drop across the connection and comparing it with a reference.

The disadvantage of this method is the low accuracy.

A known method of controlling the quality of the soldering of the EM connection [3], which consists in probing the connection of the EM windings with a eddy current meter, the sensor of which is a U-shaped emitter-receiver, covering the connection and having a receiving-emitting winding on the jumper, measure the amplitude of the received signal, by which is judged on the electrical conductivity of the soldered connection, on the basis of "experimentally established unambiguous correlation between the readings of the device and the solderedness (in%) of these connections."

The disadvantage of this method is the high complexity and low accuracy. The high complexity is due to the fact that the specified "experimental dependence" is not easy to obtain and it relates only to a specific type of compound. In addition, in the "experimental dependence" it is difficult to take into account the influence of various methodological and instrumental errors on the accuracy of measurements.

Closest to the claimed one is a method [1] for evaluating the quality of a soldered connection of EM windings, which consists in probing the connection with a eddy current meter, for which an excitation winding located on one side of the connection causes a magnetic field, which is received by a measuring winding located on the opposite side connections, measure the amplitude of the received signal, calibrate the meter before measurements, for which they probe the model ones: unsoldered, completely soldered, and then the test compound, To assess the degree of solubility of the connection of the EM windings, the ratio of the amplitudes of the received signals of the reference and the studied compounds is used.

, которая зависит от параметров обмоток, тока в обмотке возбуждения, расстояния между обмотками, толщины паяного соединения контроля и его удельной электропроводности (последние два параметра являются параметрами влияния объекта контроля). В устройстве [1] измеряют амплитуду сигнала, принятого измерительной обмоткой, т.е.

. При калибровке измеряют амплитуды принятых сигналов для пропаянного и непропаянного соединений U_п и U_н соответственно. При зондировании исследуемого соединения измеряют амплитуду принятого сигнала U_x, а степень пропаянности соединения S оценивают по формулеThe principle of operation of the method [1] is that an alternating (sinusoidal) voltage is supplied to the field winding. The current flowing through the winding creates an alternating magnetic field interacting with the metal of the test object. Eddy currents arise in the control object, the direction of which is opposite to the direction of the current in the field winding. The arising magnetic field of eddy currents is directed in antiphase to the magnetic field of the field coil and tends to weaken it. EMF is induced in the measuring winding

, which depends on the parameters of the windings, the current in the field winding, the distance between the windings, the thickness of the soldered connection of the control and its electrical conductivity (the last two parameters are the parameters of the influence of the control object). The device [1] measures the amplitude of the signal received by the measuring winding, i.e.

. When calibrating, the amplitudes of the received signals are measured for the soldered and unsoldered joints U _p and U _n, respectively. When probing the test compound, the amplitude of the received signal U _{x is} measured, and the degree of soldering of the compound S is estimated by the formula

The dependence of the complex value of U on the measuring winding on the degree of soldering of the connection is theoretically calculated, see [1], formula (1), Fig. 7. On the basis of the described principle, the eddy current quality meter of soldered joints “Constant VD1” [4] is industrially produced. The experience of its operation showed that the disadvantage of the method [1] is the low accuracy associated with the fact that the position of the field windings and the measuring one relative to the soldered joint have a significant effect on the amplitude of the signal received by the measuring winding. On the one hand, for complete control, the sizes of the field windings and the measurement windings must correspond to the sizes of the soldered connection, on the other hand, even small deviations of the position of the windings from the soldered connection lead to disruption of the shielding and a significant increase in the amplitude of the measured signal, i.e. measurement errors. The positioning accuracy of the windings is difficult to achieve, since the soldered joints under study are located close to each other, have solder bumps, deformations that occurred during soldering, etc. Attempts to solve this problem due to guides, stops, etc. mechanical structures complicated the process of taking measurements and did not give the desired result. In addition, for measurements, the size of the windings must correspond to the sizes of the soldered connection, which leads to the need for a set of coils of different sizes in the eddy current meter, which increases the cost of the product.

The problem solved by the claimed invention is to increase the accuracy and speed of measurements by ensuring their independence from the correct position of the windings relative to the soldered connection.

To solve this problem, in a method for evaluating the quality of a soldered connection of EM windings, which consists in probing the connection with a eddy current meter, for which an excitation winding located on one side of the connection causes a magnetic field in it, which is received by a coaxial measuring winding located on the opposite side connections, measure the amplitude of the received signal, calibrate the meter before measurements, for which they probe the following: unsoldered, completely soldered, and then the test compound, they determine the quality of the studied soldered connection of the EM winding, comparing the amplitudes of the signal received from it with signals from exemplary connections, when probing the connections, the phase of the received signal is additionally measured, when calibrating, the unsoldered and completely soldered connections are probed several times at different relative positions of the connection and the meter windings, and the position is calculated equidistant point of the complex plane, relative to which the amplitude of the received signals does not depend on the relative position with connections and windings, for unsoldered and soldered connections, when assessing the quality of the soldered connection of the windings of electric machines, the amplitudes of the received signals of the reference and studied compounds, calculated from an equidistant point, are used.

Significant differences of the proposed method for assessing the quality of the soldered connection of the EM windings are that:

When probing the compounds, the phase of the received signal is additionally measured, which makes it possible to determine the point of the complex plane corresponding to the measurements made, and thereby increase the accuracy of the measurements.

In the prototype, only the amplitude of the received signal is measured.

The sounding of an unsoldered and completely soldered connection during calibration, several times at different relative positions of the connection and the meter windings allows you to evaluate the degree of influence of the inaccuracy of the position of the eddy current meter windings relative to the connection.

In the prototype, calibration is carried out once.

Calculation of the position of an equidistant point on the complex plane, relative to which the amplitude of the received signals does not depend on the relative position of the connection and the windings for both soldered and soldered connections, and the use of this position when evaluating the quality of the soldered connection of the EM windings eliminates the influence of inaccurate windings on the measurement accuracy .

In the prototype, the inaccuracy of the installation of the windings is not taken into account.

The inventive method is illustrated by the following graphic materials:

FIG. 1 - complex plane, where:

, принятого измерительной обмоткой от степени пропаянности соединения при несмещенном положении обмоток относительно паяного соединения;- BCD - hodograph of the calculated dependence of the complex amplitude of the signal

adopted by the measuring winding from the degree of soldering of the connection with the unbiased position of the windings relative to the soldered connection;

, принятых измерительной обмоткой от ее смещения относительно паяного соединения.- Bb, Cc, Dd - hodographs of experimental dependences of complex signal amplitudes

taken by the measuring winding from its displacement relative to the solder joint.

FIG. 2. The eddy current meter circuitry is shown in FIG. 2, where:

1. The eddy current transformer transducer excitation generator;

2. Eddy current transformer converter;

3. Field winding;

4. Measuring winding;

5. Soldered EM connection;

6. The signal amplifier of the converter;

7. Amplitude detector;

8. Phase detector;

9. The microcontroller, the contents of the ADC and the standard digital interface unit;

10. Standard digital communication interface.

Consider the possibility of implementing the proposed method.

и фазы φ принятого сигнала, что позволяет определить соответствующую точку на комплексной плоскости (Im

, Re

). В [1], рис. 7, приведена расчетная зависимость комплексной амплитуды сигнала

, принятого измерительной обмоткой, от степени пропаянности соединения, которая представлена на Фиг. 1, кривая B-C-L-D. Точка В соответствует полностью пропаянному, D - непропаянному, а С и L - промежуточным степеням пропянности соединения. Экспериментальные исследования вихретокового измерителя позволили построить годографы зависимостей комплексных амплитуд принятых сигналов

от степени смещения обмоток относительно паяного соединения, при этом В-b - годограф для полностью пропаяного соединения, D-d - для непропаяного и С-с - для промежуточного. Точки B, C, и D соответствуют несмещенному положению обмоток и соединения.When probing soldered joints, the amplitude is measured

and phase φ of the received signal, which allows us to determine the corresponding point on the complex plane (Im

Re

) In [1], fig. 7, the calculated dependence of the complex amplitude of the signal is shown

received by the measuring winding, from the degree of soldering of the connection, which is shown in FIG. 1, BCLD curve. Point B corresponds to completely soldered, D to unsoldered, and C and L to intermediate degrees of solubility of the compound. Experimental studies of the eddy current meter made it possible to construct hodographs of the dependences of the complex amplitudes of the received signals

from the degree of displacement of the windings relative to the soldered connection, while B-b is the hodograph for a fully soldered connection, Dd is for non-soldered connection, and C-c is for intermediate. Points B, C, and D correspond to the unbiased position of the windings and the connection.

, а затем уравнение прямой линии α, проходящей через эту точку и перпендикулярной ему. Точки F₁ и F₂ равноудалены от любой точки прямой α. Аналогичные действия выполняют для непропаянного соединения: измерив положение двух точек G₁ и G₂, вычисляют координаты средней точки G отрезка G₁G₂, находят уравнение прямой линии β, перпендикулярной этому отрезку в его центре. Решая систему двух линейных уравнений, вычисляют положение равноудаленной точки Е (вектор

) - пересечения прямых α и β, которая равноотстоит от точек F₁ F₂, а также от точек G₁, G₂ по-отдельности. Таким образом, годографы Bd и Dd аппроксимируются дугами окружностей с центром в точке Е и радиусами EF₁ и E₁ соответственно. Вычисляют указанные радиусы:

и

. На основании приведенных рассуждений можно с достаточной уверенностью предположить, что дуга окружности радиуса ЕК с центром в равноудаленной точке Е достоверно аппроксимирует годограф промежуточных степеней пропаянности соединений, например, годограф Сс. Пусть для соединения произвольной степени пропаянности и неточного взаимного положения обмоток и соединения измерение амплитуды и фазы сигнала, принятого измерительной обмоткой, дало точку К фазовой плоскости (вектор

). Полученный результат можно скорректировать относительно равноудаленной точки Е:

. Амплитуда ЕК сигнала, принятого измерительной обмоткой, не зависит от относительного положения паяного соединения и обмоток, поскольку в силу сделанных выше предположений точки К и С равноудалены от точки Е.In the simplest embodiment of the inventive method, two measurements of a completely soldered compound, differing in amplitudes and phases, are performed and two different points of the phase plane F ₁ and F ₂ are obtained, FIG. 1. In the first measurement, they strive to ensure that the point F _{1 is} closer to point B, setting the windings exactly above the connection. The obtained segment F ₁ F ₂ find the midpoint

and then the equation of a straight line α passing through this point and perpendicular to it. The points F ₁ and F _{2 are} equidistant from any point on the line α. Similar actions are performed for the soldered connection: by measuring the position of two points G ₁ and G ₂ , the coordinates of the midpoint G of the segment G ₁ G ₂ are calculated, the equation of the straight line β, perpendicular to this segment in its center, is found. Solving a system of two linear equations, calculate the position of equidistant point E (vector

) is the intersection of the lines α and β, which is equally spaced from the points F ₁ F ₂ , as well as from the points G ₁ , G ₂ separately. Thus, the hodographs Bd and Dd are approximated by arcs of circles centered at point E and radii EF ₁ and E _1, respectively. The indicated radii are calculated:

and

. Based on the above reasoning, we can safely assume that the arc of a circle of radius ЕК centered at equidistant point Е reliably approximates the hodograph of intermediate degrees of soldering of compounds, for example, the Hc hodograph. Let for the connection of an arbitrary degree of soldering and inaccurate mutual position of the windings and the connection, the measurement of the amplitude and phase of the signal received by the measuring winding give a point K of the phase plane (vector

) The obtained result can be corrected with respect to equidistant point E:

. The amplitude of the EC signal received by the measuring winding does not depend on the relative position of the soldered connection and the windings, since, by virtue of the above assumptions, points K and C are equidistant from point E.

The degree of soldering of the compound S is estimated by the formula (1) using the following amplitudes of the received signals:

When only the amplitudes of the received signal are taken into account, as is done in [1], the value 0K is used as U _x , therefore, point L (0K = 0L) of the BCLD hodograph will be equidistant from the coordinate origin, which differs significantly from point C, the actual value of the degree soldering of this compound.

The above geometric considerations are elementary, therefore, the corresponding mathematical calculations in the description are not given in order to reduce the volume of the description.

A further increase in the accuracy of measurements can be achieved by carrying out calibration measurements more than two times on each exemplary compound, as indicated in the claims. This option will reduce the impact of calibration errors and errors. In this case, the measurement results are also approximated by a straight line segment, using, for example, the least squares method. All other actions remain the same.

Thus, the inventive method for assessing the quality of the soldered connection of the windings of EM can theoretically be implemented and can improve the accuracy of measurements.

Eddy Current Meter Diagram FIG. 2 is made according to the classical scheme.

The eddy current transformer transducer 1 excitation generator is intended for generating sounding signals. To ensure the required penetration depth (up to tens of millimeters), the generator frequency is tens of hertz.

The eddy current transformer transducer 2 contains two coaxial windings: excitations 3 and measuring 4. Connections of adjacent winding rods are located in close proximity to the soldered connection, therefore, to reduce their effect on the instrument readings, the windings have external ferromagnetic screens acting as magnetic field concentrators. The windings are installed opposite each other and are connected by non-magnetic pincers with an adjustable distance, which is selected in accordance with the dimensions of the studied solder joint.

The soldered joint EM 5 is an object of control.

The signal amplifier of the Converter 6 is designed to amplify the signals received by the measuring winding 4.

Amplitude 7 and phase 8 detectors are designed to measure the corresponding parameters of the received signal.

The microcontroller 9 is intended for processing measurement results and contains an analog-to-digital converter and a block of a standard digital interface 10 for communication with a higher level information system.

Exemplary compounds have the same dimensions and shape as the test compound. Non-soldered exemplary connection is made in the form of a set of glued copper conductors and compressed with a clamp through a dielectric gasket. The fully soldered sample is a monolithic copper bar.

The operation of the device is as follows.

Before measurements, exemplary measures are made of fully soldered and unsoldered joints. The measuring clamps of the eddy current transformer transducer, in which the exciting 3 and measuring 4 windings are installed, are moved apart in accordance with the size of the soldered connection.

. Амплитудный 7 и фазовый 8 детекторы оценивают соответствующие параметры принятого сигнала. Микроконтроллер 9 преобразовывает эти значения в цифровую форму и обрабатывает в соответствии с заложенными алгоритмами. При необходимости результаты обработки отправляются через интерфейс 10 потребителю.When probing with the generator 1, probing signals are generated that feed the field winding 3, receive the magnetic field passed through the soldered connection with the measuring winding, and receive an output voltage

. Amplitude 7 and phase 8 detectors evaluate the corresponding parameters of the received signal. The microcontroller 9 converts these values into digital form and processes it in accordance with the embedded algorithms. If necessary, the processing results are sent via the interface 10 to the consumer.

Before measurements of the soldered joint under study, a calibration is carried out, for which exemplary fully soldered and unsoldered joints are probed each at least two times. Four points of the phase plane are obtained: 0F ₁ and 0F ₂ , as well as 0G ₁ and 0G ₂ . In accordance with the above algorithms, the coordinates of the equidistant point E and the radii of the approximating circles EF ₁ and EG ₁ are calculated in the microcontroller 9.

The test compound is probed and the position of the point K is measured, and the radius of the approximating circle EC is calculated in the microcontroller 9.

The degree of solubility of the test compound is calculated by the formula (2).

Note that eddy current transformers 2 and windings 3 and 4 of a larger size than the solder joint can be used for measurements, since this option is equivalent to their relative displacement. In this case, a smaller number of transducers 2 may be included in the eddy current meter.

Thus, the inventive method for assessing the quality of the soldered connection of the EM windings can be implemented in practice and can improve the speed and accuracy of measurements.

The main advantages of the proposed method are the following:

- The accuracy of measuring the degree of soldering does not depend on the quality of positioning of the windings in relation to the soldered connection.

- For measurements, sufficiently universal eddy current transformers of a larger size than a soldered connection can be used.

Information sources

1. Syasko V.A. et al. Quality control of soldered joints of stator winding rods of turbogenerators at the Electrosila plant, Journal In the World of Non-Destructive Testing No. 2 (48) - June 2010

2. USSR copyright certificate SU 183820.

3. Kogan L.Kh., Ponomarev B.C. VORTEX (INDUCTION) QUALITY CONTROL OF THE SOLDERING OF CONNECTIONS OF STATORS OF ELECTRIC MACHINES -

4.http: //constanta.ru/bitrix/templates/constanta_index/images/Passport-VD1%20-%20PS.pdf.

Claims (1)

A method for evaluating the quality of the soldered connection of the windings of electrical machines, which consists in probing the connection with a eddy current meter, for which an excitation coil located on one side of the connection creates a magnetic field, which is received by a coaxial measuring winding located on the opposite side of the connection, and the amplitude of the received signal is measured , the meter is calibrated before measurements, for which the model ones are probed: unsoldered, completely soldered, and then the test compound, the qualities are evaluated about the studied soldered connection of the winding of an electric machine, comparing the amplitudes of the signal received from it with signals from exemplary connections, characterized in that when probing the connections, the phase of the received signal is additionally measured, during calibration, the unsoldered and completely soldered connection is probed several times at different relative positions of the connection and windings meter, calculate the position of equidistant point of the complex plane, relative to which the amplitude of the received signals does not depend on compound in relative position and as a winding for nepropayannyh and solder compounds to assess the degree propayannosti compound windings of electrical machines use the ratio of the amplitudes of the received signals, and the test model compounds and translated with respect to equidistant points.

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