RU2496115C1 - Diagnosis method of electric circuits containing active resistance and inductance - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: according to diagnosis method of electric circuits containing active resistance and inductance, of winding electric machines and mechanisms in particular, capacitor is additionally connected in-series to diagnosed electric circuit, alternating voltage of industrial frequency is supplied to the circuit inlet, and in mode of stable sinusoidal vibration amplitude and voltage phase shift on capacitor relative to supplied voltage are measured; also relative amplitude is measured in the form of ratio of voltage amplitude on capacitor to supplied voltage amplitude, and as diagnosed parameters value of phase shift and calculated value of relative amplitude are taken.

EFFECT: improving reliability of electric circuits diagnosis and fidelity of diagnosed parameters.

3 cl, 2 dwg, 1 tbl

Description

The invention relates to technical diagnostics and can be used to diagnose electrical circuits containing active resistance and inductance, in particular the windings of electrical machines and apparatuses.

A well-known is a method for diagnosing electrical circuits, in particular automotive electrical equipment, by the presence of current in the electrical circuit when connected to a voltage source [Sergeev AG, Yutt, V.E. Diagnosing electrical equipment of cars. - M .: Transport, 1987. - 159 p., Ill.].

The disadvantage of this method is the inability to diagnose defects in the electrical circuit, in particular automotive electrical equipment, without breaking the electrical circuit.

A known diagnostic method, selected for the prototype, using as a diagnostic parameter the time constant of the transient current in the circuit of the diagnosed electrical equipment of the car [RU 2314432 C2]. In this case, instantaneous current values are measured during the transient process and the time constant is determined.

The disadvantage of this method is significant errors in determining the time constant exponentially, arising, in particular, with inaccuracies in the determination of the steady-state current value, as well as deviations of the DC voltage supplied to the diagnosed electric circuit, which ultimately leads to a decrease in reliability diagnosing electrical circuits and the reliability of the diagnosed parameters. For example, figure 1 shows the transient process - curve 1 changes the output value, in the form of voltage at the output of the current sensor, for the adopted values of T _fact = 1c $$U_{\mathrm{at}\mathrm{from}t.f\mathrm{but}\mathrm{to}t}^{*}=\mathrm{one,}$$

where T _fact is the actual value of the time constant,

- установившееся значение указанной выходной величины в относительных единицах, определяемое по выражению $$U_{\mathrm{at}\mathrm{from}t.f\mathrm{but}\mathrm{to}t}^{*}$$

- the steady-state value of the specified output value in relative units, determined by the expression

$$U_{\mathrm{at}\mathrm{from}t.f\mathrm{but}\mathrm{to}t}^{*}=\frac{U_{\mathrm{at}\mathrm{from}t.f\mathrm{but}\mathrm{to}t}}{U_{\mathrm{from}}},$$

where U _set.fact is the steady-state value of the output value in absolute units;

U _c - the base value of the input alternating voltage of industrial frequency.

The steady-state value of the output value in Fig. 1 corresponds to line 2. To determine the time constant according to the transient graph, the fact is usually used that during time t = 3T the output value reaches 0.95 of the steady-state value.

для условий когда погрешности измерений отсутствуют. Из рисунка и проведенных расчетов следует, что значение $$\mathrm{0,95}\cdot U_{уст.факт}^{*}$$

достигается за время t=3 c, откуда измеренное значение постоянной времени совпадает с T_факт=1 c.In figure 1, line 3 corresponds to the value $$0.95\cdot U_{\mathrm{at}\mathrm{from}t.f\mathrm{but}\mathrm{to}t}^{*}$$

for conditions when there are no measurement errors. From the figure and the calculations it follows that the value $$0.95\cdot U_{\mathrm{at}\mathrm{from}t.f\mathrm{but}\mathrm{to}t}^{*}$$

achieved in time t = 3 s, whence the measured value of the time constant coincides with T _fact = 1 s.

Let us analyze the errors in the determination of the time constant that arise with errors in the measurement of the steady-state value of the output quantity. Suppose that a steady-state value is measured with an error of -2%, i.e. measured value of the output value in relative units, determined by the expression

$$U_{\mathrm{at}\mathrm{from}t.\mathrm{and}sm\mathrm{one}}^{*}=\frac{U_{\mathrm{at}\mathrm{from}t.\mathrm{and}sm\mathrm{one}}^{*}}{U_c},\left(\mathrm{one}\right)$$

. Тогда $$\mathrm{0,95}\cdot U_{уст.изм1}^{*}=\mathrm{0,931}$$

, это значение соответствует прямой 4. Из чертежа и проведенных расчетов следует, что значение 0,931 будет достигаться за время t_изм.1=3T_изм.1=2,66с. Тогда измеренное значение постоянной времени будет равно Т_изм.1=0,887, следовательно ошибка измерения составит Δ%=11,3%.makes up $$U_{\mathrm{at}\mathrm{from}t.\mathrm{and}sm\mathrm{one}}^{*}=0.98$$

. Then $$0.95\cdot U_{\mathrm{at}\mathrm{from}t.\mathrm{and}sm\mathrm{one}}^{*}=0.931$$

This value corresponds to the line 4. From the drawings and the calculations that the value 0.931 will be reached at the time t = 3T _{rev.1 rev.1} = 2,66s. Then the measured value is equal to the time constant T = 0.887 _rev.1 therefore make the measurement error Δ% = 11,3%.

. Тогда значение $$\mathrm{0,95}\cdot U_{уст.изм2}^{*}=\mathrm{0,969}$$

, этому значению на фиг.1 соответствует прямая 5. Из чертежа и проведенных расчетов следует, что это значение будет достигаться за время t_изм2=3Т_изм.2=3,47 с. Тогда измеренное значение постоянной времени Т_изм.2=1,157, а ошибка измерений составит Δ%=15,7%.Suppose that the steady-state value of the output value is measured with an error of + 2%, the measured value of the output value in relative units, determined by the expression (1), is $$U_{\mathrm{at}\mathrm{from}t.\mathrm{and}\mathrm{<figure-callout\; id="2"\; label="s\; m"\; filenames="00000022.png"\; state="\{\{state\}\}">s\; </figure-callout>}m2}^{*}=\mathrm{1,02}$$

. Then the value $$0.95\cdot U_{\mathrm{at}\mathrm{from}t.\mathrm{and}\mathrm{<figure-callout\; id="2"\; label="s\; m"\; filenames="00000022.png"\; state="\{\{state\}\}">s\; </figure-callout>}m2}^{*}=0.969$$

, This value corresponds to 1 line 5. From the calculations and drawing it follows that the value will be reached at time t = 3T _{izm2 izm.2} = 3.47 s. Then the measured value of the time constant T _ISM.2 = 1.157, and the measurement error will be Δ% = 15.7%.

Thus, in the method adopted as a prototype, inaccuracies in determining the steady-state current value, as well as deviations in the DC voltage supplied to the diagnosed electric circuit, can lead to significant errors in determining the value of the diagnosed parameter, which ultimately leads to a decrease in the reliability of diagnosing electrical chains and reliability of diagnosed parameters.

The technical result of the proposed method for diagnosing electrical circuits containing active resistance and inductance is to increase the reliability of diagnosing the parameters of electrical circuits and the reliability of the diagnosed parameters.

, где L_НОМ - индуктивность цепи с номинальными значениями электрических параметров, ω_C - частота подаваемого напряжения.The technical result is achieved by the fact that in the method for diagnosing electrical circuits containing active resistance and inductance, in particular windings of electrical machines and apparatuses, a capacitor is additionally connected in series to the diagnosed electrical circuit, an alternating voltage of industrial frequency is supplied to the input of the circuit, and measured in the mode of steady harmonic oscillations the amplitude and phase shift of the voltage across the capacitor relative to the applied voltage, calculate the relative amplitude at voltage in the form of the ratio of the amplitude of the voltage across the capacitor to the amplitude of the applied voltage and the phase shift value and the calculated value of the relative amplitude are taken as diagnosed parameters, and the value of the capacitance of the capacitor is selected from the resonance condition by the expression $$C=\frac{\mathrm{one}}{{\mathrm{<figure-callout\; id="2"\; label="\omega \; C"\; filenames="00000022.png"\; state="\{\{state\}\}">\omega \; </figure-callout>}}_C^{}\cdot L_{N\mathrm{ABOUT}M}}$$

where L _NOM is the inductance of the circuit with nominal values of electrical parameters, ω _C is the frequency of the applied voltage.

напряжения в диагностируемой электрической цепи по сравнению с относительной амплитудой $$U_{mН}^{*}$$

напряжения в цепи с номинальными электрическими параметрами определяют по выражениюIn addition, the deviation of the relative amplitude $$U_{mD}^{*}$$

voltage in the diagnosed electric circuit compared to the relative amplitude $$U_{mN}^{*}$$

voltage in a circuit with rated electrical parameters is determined by the expression

$${\Delta }_{\mathrm{one}}=\frac{U_{mN}^{*}-U_{mD}^{*}}{U_{mN}^{*}}\cdot \mathrm{one\; hundred}\%.\left(2\right)$$

In addition, the deviation of the phase shift φ _D in the diagnosed electrical circuit compared to the phase shift φ _NOM in the circuit with rated electrical parameters is determined by the expression

$${\mathrm{<figure-callout\; id="2"\; label="\Delta "\; filenames="00000022.png"\; state="\{\{state\}\}">\Delta </figure-callout>}}_2=\frac{{\varphi }_{N\mathrm{ABOUT}M}-{\varphi }_D}{{\varphi }_{N\mathrm{ABOUT}M}}\cdot \mathrm{one\; hundred}\%.\left(3\right)$$

Improving the reliability of diagnosis is achieved due to the high sensitivity of the adopted diagnostic parameters to changes in the electrical parameters of the circuit caused, in particular, by windings in the windings of electrical machines and apparatuses.

The use of the relative value of the voltage amplitude at the capacitor as a diagnosed parameter in the invention eliminates errors in case of deviations of the voltage supplied to the diagnosed electric circuit. In this case, the amplitude of the supplied alternating voltage and the amplitude of the voltage across the capacitor are simultaneously changed, and the value of the relative amplitude remains unchanged.

In the invention, the diagnosed parameters are measured in steady-state mode. A mode close to steady state in the electric circuit after applying an alternating voltage of industrial frequency to it occurs after a time equal to (10 ... 20) T, where T = R * C is the time constant of the electric circuit [Bessonov, L.A. Theoretical foundations of electrical engineering. - M .: "Higher School", 1996. - 623 p., Ill.]

The value of the relative amplitude of the voltage in the electric circuit with rated electrical parameters is determined experimentally or can be calculated by the expression [L. Bessonov Theoretical foundations of electrical engineering. - M .: "Higher School", 1996. - 623 p., Ill.]

$$U_{mN}^{*}=\frac{\mathrm{one}}{R_H}\cdot \sqrt{\frac{L_H}{C}}.$$

The phase shift of the voltage across the capacitor relative to the applied voltage in the electrical circuit with rated electrical parameters is φ _NOM = -90 e. hail.

As an example of a diagnosed electric circuit containing active resistance and inductance, the phase winding of the stator of an automobile generator 94.3701 is taken. Nominal values of the electrical parameters of the winding: the number of turns W _Ф = 48, L = 0.001447 H, R = 0.0373 Ohms.

, где L_НОМ - индуктивность цепи с номинальными значениями электрических параметров, ω_c - частота подаваемого напряжения.To implement the method for diagnosing electrical circuits containing active resistance and inductance, a capacitor C is additionally connected in series to the stator phase winding, the capacitance of which is selected from the resonance condition by the expression $$C=\frac{\mathrm{one}}{{\mathrm{<figure-callout\; id="2"\; label="\omega \; C"\; filenames="00000022.png"\; state="\{\{state\}\}">\omega \; </figure-callout>}}_C^{}\cdot L_{N\mathrm{ABOUT}M}}$$

where L _NOM is the inductance of the circuit with the nominal values of the electrical parameters, ω _c is the frequency of the applied voltage.

The values of the diagnosed parameters of the stator phase winding with rated electrical parameters obtained by calculation and simulation are shown in the second column of the table.

Diagnostic parameter The value of the diagnosed parameter Deviation of the diagnostic parameter,% in an electrical circuit with rated electrical parameters in an electrical circuit with interturn circuit one 2 3 four Relative Capacitor Voltage Amplitude 12,2 4.21 65.5 Phase Shift hail -90 -17 81.1

As a result of experimental studies, it was found that in case of a defect in the form of an inter-turn circuit of 5 turns of the stator phase, the inductance and active resistance of the circuit being diagnosed have the values: L = 0.00112 H, R = 0.0318 Ohm.

The values of the diagnosed parameters of the stator phase winding with the indicated damage to the winding turns obtained experimentally and by simulation are shown in the 3rd column of the table.

Deviations of the values of the diagnosed parameters calculated by the expressions (2), (3) are given in the 4th column of the table.

The results obtained indicate a high sensitivity of the diagnostic parameters used in the proposed method to changes in the electrical parameters of the diagnosed electric circuit caused, in particular, by inter-turn faults. For the stator phase winding damage considered in the example, the change in relative amplitude is 65.5%, the change in phase shift is 81.1%.

The measurement circuit of FIG. 2 consists of a series-connected AC voltage source of industrial frequency 1, a switching device 2, a diagnosed electric circuit 3 with an additional series-connected capacitor, a measuring and computing device 4, the input of which is connected to the output of the switching device 2 and the recording device 5 based on PC.

Measurements are made as follows. Using a switching device 2 diagnosed electrical circuit 3 is connected to a source 1 of an alternating voltage of industrial frequency. Using the measuring and computing device 4, after applying an alternating voltage, a time delay equal to (10 ... 20) R * C is ensured for steady-state operation, in the mode of steady-state harmonic oscillations, instantaneous voltage values across the capacitor are measured, the values of diagnosed parameters are determined and by the expressions ( 2), (3) deviations of the diagnosed parameters from their nominal values are calculated. The resulting deviations of the diagnosed parameters are transmitted and stored in the recording device 5.

As shown by experimental and calculated results, the values of the accepted diagnostic parameters change significantly in the presence of a defect in the diagnosed electric circuit, which allows for high reliability of diagnosis.

Claims (3)

1. A method for diagnosing electrical circuits containing active resistance and inductance, in particular, windings of electrical machines and apparatuses, by applying voltage to the electrical circuit and comparing the values of the measured diagnosed parameters in the diagnosed electrical circuit and circuit with nominal values of electrical parameters, characterized in that a capacitor is additionally sequentially connected to the diagnosed electric circuit, an alternating voltage of industrial frequency is fed to the input of the circuit, and In the mode of steady-state harmonic oscillations, the amplitude and phase shift of the voltage across the capacitor are measured relative to the applied voltage, the relative amplitude is calculated as the ratio of the amplitude of the voltage across the capacitor to the amplitude of the applied voltage, and the phase shift value and the calculated value of the relative amplitude are taken as diagnosed parameters, and the capacitor capacitance value is selected from the resonance condition by the expression $$C=\frac{\mathrm{one}}{{\omega }_C^2\cdot L_{N\mathrm{ABOUT}M}},$$

where L _NOM is the inductance of the circuit with nominal values of electrical parameters, ω _C is the frequency of the applied voltage. 2. The method according to claim 1, characterized in that the deviation of the relative amplitude $$U_{mD}^{*}$$

voltage in the diagnosed electric circuit compared to the relative amplitude $$U_{mN}^{*}$$

voltage in a circuit with rated electrical parameters is determined by the expression
$${\Delta }_{\mathrm{one}}=\frac{U_{mN}^{*}-U_{mD}^{*}}{U_{mN}^{*}}\cdot \mathrm{one\; hundred}\%.$$

3. The method according to claim 1, characterized in that the deviation of the phase shift φ _D in the diagnosed electrical circuit compared to the phase shift φ _NOM in the circuit with rated electrical parameters is determined by the expression
$${\Delta }_2=\frac{{\phi }_{N\mathrm{ABOUT}M}-{\phi }_D}{{\phi }_{N\mathrm{ABOUT}M}}\cdot \mathrm{one\; hundred}\%.$$

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