RU2659310C1 - Device for searching turn-to-turn short circuits in inductance coils - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention relates to measuring equipment. Essence: device for searching turn-to-turn short circuits in inductance coils contains a transformer whose secondary winding is connected through the diode to the storage capacitor and to the serial circuit, consisting of a winding being checked, an electronic power switch controlled from the control unit. Primary winding of the transformer is connected through the electronic switch of the converter to a DC voltage source. Electronic switch of the converter is controlled from the PWM output of the controller. Current sensor is connected in series with the electronic power switch. Current sensor output is connected via the second peak detector to the information input of the second comparator. Voltage from the storage capacitor is fed through the voltage divider on the resistors and through the matching unit to the feedback input of the PWM controller, to the input of the first peak detector and to the input of the differentiator. From the output of the differentiator, the voltage is fed through the rectifier ad through the third comparator to the input of the control unit. Output of the first peak detector is connected to the input of the first comparator and to the reference input of the second comparator. Output of the first comparator is connected to the circuit indicator and the first input of the logic unit. Second input of the logic unit is connected to the output of the second comparator. Output of the logic unit is connected to the indicator of turn-to-turn short circuits.

EFFECT: technical result: increase in the reliability and accuracy of detecting turn-to-turn short circuits.

1 cl, 2 dwg

Description

The invention relates to measuring technique, in particular to a device for searching for short circuits in inductors.

Devices for searching for short circuits (VZ) using capacitive drives and operating on the principle of charging a storage capacitor from a power transformer and then discharging it through an electronic key to the tested winding or inductor inductively connected to the tested winding have been known for a long time.

For example, in a device (USSR AS 82724, declared March 11, 1948, No. 378531, published May 31, 49), the storage capacitor is charged through a gasotron, and then discharged through an electronic key (thyratron) to the tested winding.

Later, semiconductor elements (diodes, thyristors, transistors) began to be used in devices instead of electron tubes.

For example, in a device (Shustov MA Practical circuitry. Voltage converters. Book 3. Altex-A. Moscow, 2002, Fig. 11.13), a generator circuit on a capacitive storage is shown. During the positive half-cycle of the mains voltage, the storage capacitor is charged through the resistor and diode with the thyristor closed. At a negative half-wave, the diode closes, and the thyristor opens, and the storage capacitor discharges to the load.

This is an example of a classic capacitive storage generator circuit used in high-voltage search devices.

Closest to the claimed is a device created under the guidance of V.V. Shumeyko (AP Zelenchenko. Diagnostic devices for traction engines of electric rolling stock. Textbook. Moscow, 2002, p. 19).

In the positive half-cycle of the network, an accumulative capacitor is charged through the open diode from the output winding of the power transformer. In this case, the discharge thyristor of the storage capacitor is closed.

In the negative half-cycle of the network, the diode closes, and the storage capacitor ceases to charge (it is already charged in the positive half-period of the network to the voltage amplitude from the output winding of the power transformer).

In this case, the control unit generates pulses that open the thyristor and the storage capacitor is discharged to an inductor, which is inductively connected to the tested winding - the discharge current of the storage capacitor is formed.

A signal proportional to the discharge current is removed from the sensor inductively coupled to the tested winding and is fed to the display unit.

If available The discharge current increases and the signal from the sensor increases, which is recorded by the display unit.

This device, like other similar ones, based on the capacitive energy storage devices described above, has the following disadvantages:

- The efficiency of the charge circuit of the storage capacitor (secondary winding of the power transformer - diode - storage capacitor) is theoretically less than 50%, which is proved in the book (Circuit Design and the Use of Powerful Pulse Devices. Hanshiohim Bloom, trans. From English M. Dodeka. XXI, 2008, p. 203).

- the power transformer due to the unipolar load (diode - storage capacitor) operates on a partial hysteresis loop with an induction amplitude of 4 times less than the maximum (Calculation of electromagnetic elements of secondary power sources. A.N. Gorsky and others M.Radio and communication, 1988 , p. 21).

Therefore, the mass of the transformer magnetic circuit must be increased 4 times in comparison with a transformer operating on a full hysteresis loop at the same power consumption.

- The instability of the voltage at the storage capacitor is due to the lack of voltage stabilization on it, which is difficult to perform in this configuration of the charge circuit of the storage capacitor. Therefore, the sensitivity of the device is reduced due to fluctuations in the measured discharge current of the storage capacitor.

- The difficulty of adjusting the voltage across the storage capacitor. Usually this is done by introducing the LATR power transformer into the primary winding circuit, which, like the transformer, will have an increased mass. Therefore, in portable devices, as in the prototype, the adjustment of this voltage is not performed.

- Reduced sensitivity of the device due to the natural discharge of the storage capacitor in the peak detector, which detects the discharge current of the storage capacitor. In the prototype, the circuit for fixing the discharge current is an integral part of the display unit and is not shown separately.

The basis of the invention is the task of increasing the sensitivity of the device and increasing its efficiency by eliminating all of the aforementioned disadvantages through the use of a high-frequency method of charging a storage capacitor using feedback tracking the voltage at the storage capacitor and tracking the voltage at the reference input of the comparator for the voltage amplitude at the storage capacitor and behind the discharge voltage of the storage capacitor of the peak detector fixing the discharge current.

The problem is solved in that in a device for searching for short circuits containing a transformer, the secondary winding of which is connected via a diode to a storage capacitor and to a series circuit consisting of a tested winding of an electronic power key controlled by a control unit, according to the invention, the primary winding of the transformer through the electronic key of the converter is connected to a constant voltage source, and the electronic key of the converter is controlled from the output of the PWM controller, additional The current sensor is additionally connected in series with the electronic key, the output of the current sensor through the peak detector of the second is fed to the information input of the second comparator, the voltage from the storage capacitor through the voltage divider through the resistors and through the matching unit is fed to the feedback input of the PWM controller, to the input of the peak detector of the first and to the input of the differentiator, and from the output of the latter through the rectifier, the comparator, the third is fed to the input of the control unit, the output of the peak detector of the first is connected to the input of the comparator of the first and to the reference input of the comparator of the second, the output of the comparator of the first goes to the circuit indicator and to the first input of the logic unit, and the signal from the output of the comparator of the second is connected to its second input, the output of the logical unit is connected to the indicator of coil circuits.

The increase in sensitivity is ensured by the stabilization of the voltage of the full charge of the storage capacitor and the monitoring of the voltage at the reference input of the comparator, both by the amplitude of the voltage at the storage capacitor and the discharge voltage of the storage capacitor of the peak detector designed to fix the discharge current.

An increase in efficiency up to 90% is achieved through the use of a high-frequency method of charging a storage capacitor. At the same time, the transformer has small dimensions, as it operates at a high frequency.

In addition, it is easy to adjust the amplitude of the stabilized voltage at the storage capacitor by changing the feedback depth of the PWM controller, for example, by changing the value of one of the resistors of the divider, if it is replaced by a trimmer. This allows you to configure the device to search vz. in coils with a wide range of inductances and with different requirements for the value of the test voltage between the turns of the tested coil.

The inventive device is illustrated by the following graphic materials:

FIG. 1 is a diagram of a device where:

1 - constant voltage source

2 - transformer

3 - electronic key converter

4 - PWM controller

5 - diode

6 - storage capacitor

7, 8 - resistors of the voltage divider

9 - matching unit

10 - differentiator

11 - peak detector first

12 - comparator first

13 - second comparator

14 - circuit indicator

15 - logical block

16 - indicator of turns

17 - tested winding

18 - power electronic key

19 - current sensor

20 - peak detector second

21 - rectifier

22 - third comparator

23 - control unit.

FIG. 2 - stress diagrams, where:

24 - control pulses

25 - voltage across the storage capacitor

26 - voltage output rectifier 21

27 - threshold of the third comparator 22

28 - pulses from the output of the comparator of the third 22

29 - discharge current

30 - voltage at the information input of the comparator of the second 13 in the presence of VZ

31 - voltage at the reference input of the comparator of the second 13

32 - voltage at the information input of the comparator of the second 13 in the absence of VZ

The DC voltage source 1 creates a current through the primary winding of the transformer 2 when the electronic switch 3 is open. No current when the latter is closed.

The electronic key is controlled by the PWM controller 4 chip.

The output of the transformer through the diode 5 charges the storage capacitor 6, and this voltage through the divider on the resistors 7 and 8 and through the matching unit 9 is supplied as a voltage feedback signal to the input of the PWM controller.

At the same time, this voltage is connected to the input of the differentiator 10 and to the input of the peak detector of the first 11, the output of which is connected to the input of the comparator of the first 12 and to the reference input of the comparator of the second 13.

The output of the comparator of the first goes to the indicator of the circuit 14 and to the first input of the logical unit 15, and to its second input, the signal from the output of the comparator of the second.

The output of the logic block is fed to the indicator 16.

The storage capacitor is discharged to the tested winding 17 through an electronic key power 18, for example, a thyristor.

The discharge current from the current sensor 19 through the peak detector of the second 20 is fed to the information input of the comparator of the second.

The device operates as follows:

The high-frequency converter is made on the PWM chip of the controller 4, the electronic key of the converter 3, for example, a field-effect transistor, transformer 2, a constant voltage source 1, a rectifier 5 and a storage capacitor 6 according to one well-known flyback converter circuit (in the English literature - flyback converter), which depends from the selected PWM controller chip.

When the electronic key of the converter 3 is open, the current through the primary winding of the transformer 2 increases linearly and energy is accumulated in the transformer. When the electronic key of the converter is closed, the energy from the transformer from its secondary winding through the open diode 5 is discharged to the storage capacitor 6.

In FIG. 2 shows control pulses 24 from the PWM controller output. A portion of energy from the transformer recharges the storage capacitor with each control pulse. The voltage across the storage capacitor has the form 25 (charge steps not shown). The number of such cycles of energy transfer depends on the required energy on the capacitor when it is fully charged and a portion of the energy transferred per cycle and is selected based on the optimal criteria when calculating a high-frequency converter with the required charge time of the storage capacitor.

The use of a flyback converter is due to the fact that it is not afraid of output short circuits. For example, when the electronic key 18 is opened and the storage capacitor 6 is discharged to the tested winding and a discharge current is generated, the current from the output winding of the flyback converter does not exceed the value determined by the energy reserve per cycle, and this current is much less than the discharge current.

If another version of the converter is used, for example, a straight-through converter, the device circuitry will need to be complicated - it is necessary to disconnect the converter for the duration of the discharge capacitor discharge to exclude a short circuit at the converter output.

When the voltage at the storage capacitor 6 reaches the required value, then this voltage stabilizes (horizontal section on the voltage line 25) due to the feedback on the chain: the resistors of the divider 7 and 8 are the matching unit, 9 is the feedback input of the PWM controller 4.

The amplitude of this voltage is stored by the capacitor of the peak detector of the first 11 and from its output in the form of voltage 31 is supplied as a reference to the input of the comparator of the second and to the input of the comparator of the first.

In addition, the voltage across the storage capacitor through the divider and matching unit is differentiated by the differentiator 10 and after rectification by the rectifier 21 will have the form of voltage 26. This voltage is supplied to the input of the third comparator 22, where it is compared with the threshold voltage 27 (in Fig. 1, the reference input of the third comparator for supplying voltage 27 is not shown, since this can be provided by various circuitry solutions, for example, by limiting the input voltage 27) and at the output of this comparator at a voltage of 26 less e threshold 27 are formed pulses 28 which via the control unit 23 opens the power key 18. As can be seen from the diagrams of voltages pulses 28 are generated when the voltage on the storage capacitor reaches a voltage stabilization. In the control unit 23, a delay for opening the electronic key of the power 18 can be provided for a guaranteed exit to the stabilization mode (this delay for opening is realized in the control unit 23 of the device and is equal in time to the length of the horizontal section on voltage line 25).

When, after this delay, the electronic power switch is opened, the storage capacitor is discharged, the pulses 28 from the output of the third comparator are automatically removed, and a discharge current 29 is generated, which is shown for the option to use the thyristor as an electronic power switch 18. The negative half-wave of this current closes the thyristor, and the voltage at the storage capacitor will be recharged to the opposite polarity (the energy from the tested winding 17 is returned to the energy at the storage capacitor 6). Therefore, the beginning of each charge cycle of the storage capacitor begins with its recharging from reverse polarity to zero, and then the charge, as shown in the voltage curve 25 on the storage capacitor.

The amplitude of the discharge current from the output of the current sensor 19 is stored on the capacitor of the peak detector of the second 20 and in the form of a voltage of 32 (if there is no voltage) or voltage 30 (if there is a voltage) is fed to the information input of the comparator of the second 13.

The voltage 31 is supplied to the reference input of this comparator from the output of the peak detector of the first 11.

If there is a circuit (there is a voltage of 31 from the output of the peak detector of the first 11), then the output of the comparator of the first 12 will be a logical unit (positive voltage) and the indicator of circuit 14 will be lit, and a logical unit at the first input of the logical block allows its operation (the logical block repeats signal level from the output of the second comparator).

If there is no circuit (voltage 31 is close to zero), for example, the converter does not work, then the output of the comparator of the first 12 will be logic zero (zero voltage) and the circuit indicator will not light, and logic zero will inhibit the operation of the logic block (at the output of the logic block always there will be zero voltage and the indicator of turn-in circuits will not light).

If there is a wc in the tested winding 17, then the discharge current increases, and the voltage 30 at the information input of the comparator of the second 13 becomes higher than the voltage 31 at its reference input and the output of this comparator will be a logical unit, which, if there is a circuit, is repeated by a logical unit and both indicators will light (indicator circuit and indicator of turns).

If not vz in the tested winding 17, then the discharge current will be less than with the high voltage. and the voltage 32 at the information input of the comparator of the second 13 will become less than the voltage 31 at its reference input and the output of this comparator will be a logical zero, which, if there is a circuit, is repeated by a logical unit and the circuit indicator will light and the loop circuit indicator will not light.

To eliminate the influence of interference on the reference input of the comparator of the first 12, a voltage is supplied above the level of interference, but below the level of the useful signal from the output of the peak detector of the first 11, when the converter is working (in Fig. 1, the reference input of the comparator of the first is not shown, since this is not important). This is easily ensured since the level of this useful signal is much higher than the level of interference.

An essential factor increasing the sensitivity of the device is the condition that the discharge constant of the capacitor of the peak detector of the first 11 is equal to the constant of the discharge time of the capacitor of the peak detector of the second 20. In this case, as shown in FIG. 2, the reference voltage 31 at the reference input of the comparator of the second 13 is reduced, as well as the voltage at the information input of this comparator 30 or 32 is reduced (the lines of these voltages are almost parallel). Thus, the voltage at the reference input of the comparator 13 indirectly monitors its input voltage at the information input.

Therefore, the voltage 32 without coil faults or 30 with coil faults at the information input of the comparator 13 can be located as close as possible to the voltage level 31 at its reference input, which means that the device will detect minimal changes in the discharge current, which increases the sensitivity of the device.

Given the fact that fluctuations in the discharge current due to voltage fluctuations on the storage capacitor are insignificant, due to voltage stabilization on this capacitor, this further increases the sensitivity of the device.

In general, the device has greater sensitivity compared to the prototype.

PWM controller 4 - a standard microcircuit for switching power supplies, for example, it can be selected from those described in the manual (Microcircuits for switching power supplies and their application. 2nd ed., Rev. And add. - M.: Dodeka Publishing House XXI ", 2001, 608 pp.).

As a differentiator, the capacitor-resistor circuit itself can be used, and the simplest version of the peak detectors 11, 20 is the diode-capacitor chain. To improve the accuracy of the differentiator 10, the peak detectors 11 and 20 and the comparators 12, 13, 22 can be performed on operational amplifiers, for example, according to the schemes (Shustov MA Circuitry. 500 devices on analog microcircuits. - St. Petersburg: Science and Technology , 2013 .-- 352 p.).

The logical unit 15 performs the simplest logical function and is easily implemented on logical elements.

The thyristor or other electronic power switch is controlled by well-known standard circuits.

As a current sensor 19, a resistor can be used.

The transformer 2 is high-frequency and is performed, for example, using ferrite material as a magnetic circuit.

The DC voltage source 1 is, for example, a battery, or a transformerless rectifier with a capacitive filter or any other option. Moreover, the stabilization of the constant voltage source 1 is not required.

Thus, the practical implementation of the device is not difficult.

For research, a prototype of the IVZ-MU-02 device was manufactured, in which the electronic key of the converter was made on an IRFBC40 field-effect transistor, the electronic power key was made on a TB2333-250 thyristor, and the PWM controller was on an MC33063 chip.

The tests were carried out at the Electrotyazhmash plant. Search vz was performed in the coils of traction units A723MU2, A721AU2, A728AU2 before and after installing them in the stator.

With a storage capacitor capacitance of 8 μF, the pulse test voltage exceeded 500 V with a discharge current amplitude of more than 300 A. High sensitivity of the device was experimentally confirmed, and its high efficiency ensured its small dimensions.

Claims (1)

A device for searching for short circuits in inductance coils, containing a transformer, the secondary winding of which is connected via a diode to a storage capacitor and to a series circuit consisting of a tested winding, an electronic power key with control from the control unit, characterized in that the primary winding of the transformer through an electronic key the converter is connected to a constant voltage source, and the electronic key of the converter itself is controlled from the output of the PWM controller, in addition, therefore, the current sensor is turned on with the power electronic switch, the current sensor output through the peak detector of the second goes to the information input of the second comparator, the voltage from the storage capacitor through the voltage divider through the resistors and through the matching unit goes to the feedback input of the PWM controller, to the input of the peak detector of the first and to the input of the differentiator, and from the output of the latter through the rectifier, the third comparator is fed to the input of the control unit, the output of the peak detector of the first is connected to the input of the computer Ator first and second reference input of the comparator, the comparator output is supplied to a first indicator circuit and the first input of a logical block, and on its second input connected to the output signal of the second comparator, logic unit output is connected to the indicator interturn fault.

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