RU192779U1 - The device for determining the labels "start" and "end" of the windings of a three-phase asynchronous AC motor with squirrel-cage rotor - Google Patents

Abstract

The essence of the claimed solution lies in the fact that the device for determining the labels "start" and "end" of the windings of a three-phase asynchronous AC motor with a squirrel-cage rotor contains a power battery (galvanic cell), additionally contains a microcontroller (MK) with programmed control with built-in multi-channel analog digital converter (ADC) and control inputs / outputs; switching key for the formation of a differential current; measurement preparation switching key; diagnostic switch key; indication unit; start button for the process of determining labels; contact block; battery power; moreover, three control outputs of the MC are connected to the control inputs of the switching key for generating the differential current, the switching key of the preparation of measurements, the switching key of diagnostics, the group of control outputs of the MK is connected to the control inputs of the display unit, one control input of the MK is connected to the start button of the label determination process, to the ADC inputs connected the positive output of the battery, the output of the diagnostic switch key, four outputs of the measurement preparation switch key, to the switching input of the diagnostic key are connected to the positive and negative poles of the power battery, the positive pole of the power battery is also connected to the input of the switching key for generating a differential current, the negative pole of the power battery is also connected to the contact "end" of the first pair of contact block, one output of the switching key for generating the differential current is connected to contact "start" of the first pair of contact block, the second output of the switching key of the formation of the differential current is connected to contact "end" of the first pair of block and the contacts, the four outputs of the second and third pairs of the contact block are connected to the inputs of the measurement preparation switching key. The technical result in the implementation of the claimed solution is to improve the usability of the device by creating a portable stand-alone device, which, using a single connection to the engine, quickly, in one measurement, determines labels “start” and “end” at once to all its windings with the possibility of application for engines with a wide range of powers. 8 ill.

Description

The device relates to electrical engineering and is intended to control and determine the labels "start" and "end" of the terminals of the windings of a three-phase asynchronous AC motor with squirrel-cage rotor (hereinafter referred to as the motor).

Labels “beginning” and “end” of the terminals of the motor windings are mandatory elements of its device. With their help, the windings in the motor are connected in a "star" or "triangle" circuit (figures 1a, 1b).

Ultimately, the labels allow you to orient all three windings to a coordinated work on converting an external three-phase voltage into a circular magnetic field and, as a result, ensure the operation (rotation) of the motor in the calculated mode.

If one of the windings of a serviceable motor interchanges the conclusions (which is equivalent to interchanging the “start” and “end” labels), then the “star” or “triangle” circuit will be connected incorrectly. Then the mutual coordination of the windings in a single direction of rotation is violated in the motor. The rotational effect of this winding will be directed counterclockwise to the effects of the other two. In this case, when an external three-phase voltage is applied, the motor will be in an off-design electromagnetic mode and may fail (the windings may burn out).

During the operation of electrical installations, situations often arise when the engines for some reason have lost these marks (after repair, after transportation, etc.). The fact that turning the motor on to the wrong connection of the windings can damage it, makes it necessary to check the correctness of the “start” and “end” winding marks before turning it on under operating voltage. The proposed device effectively solves this problem.

A known method (device) for determining the labels "start" and "end" of the motor windings, presented in figure 2 (a, b, c, d).

It consists in the fact that from the source of alternating voltage, a measuring voltmeter of alternating current and three motor windings, four variants of circuits are assembled, and measurements are made for each variant. Those. Four successive experiments are reproduced in which four versions of a single-phase transformer are combined from the motor windings. In the primary winding of this transformer, one winding is used, and in the secondary - the two remaining windings connected in series.

In the first experiment (figure 2 a), the primary winding of a single-phase transformer is winding "A". An AC voltage source is connected to its terminals through a switch. The conclusions of the winding "B" immediately randomly marked on the "beginning" and "end". Then the windings "B" and "C" are connected in series so that the "end" of the winding "B" is connected to one of the terminals of the winding "C". A voltmeter is connected to the two terminal leads of this dual winding. Then, an alternating voltage is applied to the “A” winding and the induced EMF in the dual winding is measured and recorded with a voltmeter.

In the second experiment (figure 2 b), the connection of the winding "A" remains the same, and the serial connection of the winding "C" to the winding "B" changes its polarity, i.e. to the "end" of the winding "B" is connected to another terminal of the winding "C". After that, the EMF is also measured at the terminals of the dual winding.

Based on the results of two experiments, conclusions are drawn. For the experience in which the measured EMF was greater, it is concluded that its windings worked in concert. Then, for this experiment, the output of the “C” winding, which was connected to the “end” of the “B” winding, gets the label “start”, and the other - “end”. The winding marks “B” and “C” after the first two experiments were determined.

In the third and fourth experiments (figure 2 c, d) the winding marks “A” are determined. In them, the primary winding of a single-phase transformer is the "B" winding. The secondary winding is formed by sequential connection to the "end" of the winding "C" conclusions of the winding "A". Similarly to experiments 1 and 2, the induced EMF is measured on a dual secondary winding, and conclusions are drawn about assigning labels to the terminals of the "A" winding.

The device selected as a prototype is another known method (device) for determining the labels "start" and "end", presented in figure 3 (a, b, c, d).

It consists in the fact that four variants of circuits with a single-phase transformer are assembled from a battery (galvanic cell), a sensitive magnetoelectric switch millivoltmeter of direct current and three motor windings, and measurements (experiments) are made for each variant.

In all experiments, the primary winding of a single-phase transformer is the winding "A" ("disturbing"). The assignment of the designations "A", "B", "C" to the windings is arbitrary. The conclusions of the winding "A" are immediately randomly marked at the "beginning" and "end". The battery is connected to the conclusions of the winding "A" through the switch, and the negative pole of the battery is connected to the "end" of the winding "A".

In the first and second experiments, the secondary winding of a single-phase transformer is the "B" winding. A DC pointer voltmeter is connected to its conclusions. The polarity of connecting the terminals of the voltmeter to the winding "B" in the experiments varies. (Hereinafter, these two measurement options with a change in the polarity of the connection of the voltmeter to the motor winding are called measurements in forward and reverse polarity.).

By means of a switch, voltage is applied to the primary winding "A" from the battery, as a result of which a current pulse arises in the "A" winding, which in turn causes an induction "echo" in the "B" winding. This fact is recorded by a voltmeter, and the direction of deviation of the arrow of the voltmeter in each experiment is recorded. In the experiment in which the voltmeter needle deviated to the right on the scale, the output of the “B” winding connected to the positive terminal of the voltmeter is marked as “beginning” and the other as “end”.

In the third and fourth experiments, the secondary winding is the winding C. Similarly to experiments 1 and 2, for its conclusions in experiments 3 and 4, the “beginning” and “end” are determined.

Both methods (devices) have significant drawbacks. The main one is that they are inconvenient in operation.

The following circumstances are typical for operation (especially for production conditions): a tight time limit for solving a problem; tightness of the space in the place for work, difficult access to the engine; many factors that make it difficult for a person to do manual and mental work.

The inconvenience of the operation of the above methods (devices) is due to the following reasons:

1. The process of determining labels should be preceded by preliminary preparation, which requires a significant investment of time, materials, labor.

2. The process of identifying labels is divided into four technologically separated fragments.

3. The process of identifying labels is long and does not have clear time boundaries;

4. The measurement device is limited in mobility.

5. The device does not have universality for the entire power range of engines.

The objective of the utility model (technical result) is to improve the usability of the device by creating a portable wearable stand-alone device, which, using a single connection to the engine, quickly, in one measurement, determines the labels “start” and “end” at once to all its windings with the possibility of using this device on engines of all capacities.

The task is achieved by applying the prototype method in the proposed device, including: a microcontroller (with an ADC) with software, three switching keys, two batteries, an indication unit and a contact block.

The block diagram of the device is shown in figure 4, where:

1. battery current pulse in the "disturbing" winding "A" of the motor;

2. a microcontroller (MK) with program control, containing a multi-channel analog-to-digital converter (ADC), and control inputs / outputs;

3. battery power circuits of the device;

4. A switching key for generating a current pulse, under the control of a signal from the MC, connects and disconnects battery 1 to the terminals of the "disturbing" motor winding.

5. The switching key for measuring the induction “echo”, provides the ADC connection to the terminals of the windings “B” and “C”, in different polarity, to measure the potential of the induction “echo” from the “disturbing” winding in them.

6. diagnostic switching key, provides connection of battery terminals 1 to the ADC to control its charge level

7. indication unit;

8. start button for the process of determining labels;

9. contact block (designed for channeling the outputs of the motor windings to the inputs of the switching keys of the device). All contacts of the block are grouped in three pairs, designated as “A”, “B”, “C”. In each pair, the contacts are labeled “start” and “end”.

From the user's point of view, the procedure for using the device is as follows:

The user brings the device to the engine and connects the contacts of the terminal block of the device to the terminals of the motor windings with a set of connecting wires. The motor leads must be pre-grouped into winding pairs. The connection of the pairs of motor terminals to the pairs of the block of contacts on the device is arbitrary.

The user turns on the power to the device. After a short delay, the instrument displays the Ready state. This means, firstly, that the power of the device is turned on, and secondly, that the charge level of both batteries is normal and you can start the process of determining labels. If at this stage the device reflects the “Error” state, it means that the charge level of one of the batteries or both is insufficient at once to get a reliable result, and they need to be replaced.

After receiving the “Ready” signal, the user presses the start button for the label definition process. The display unit during the process reflects the status “Process in progress”.

Upon completion of the tagging process, the following results are possible:

"Full match tags." This means that the measurement by the device was successful, that the labels of the motor leads fully correspond to the marks of the block of contacts of the device to which they are connected;

“Change the labels in winding A.” This means that the measurement by the device was successful, that the conclusions of the motor winding connected to the pair “A” of the block of contacts of the device should receive labels opposite to those indicated on these contacts, and the remaining conclusions of the motor correspond to the marks of the block of contacts of the device to which they are connected .

“Change labels in winding B” (similar to clause 4.2, but with respect to winding “B”).

“Change labels in winding C” (similar to clause 4.2, but with respect to winding “C”).

"Mistake". At this stage, this state means that the measurement by the device was unsuccessful. The reason for this may be poor contact between the terminals of the device and the terminals of the motor, improper breakdown of the motor windings into winding pairs, open windings, inter-turn short circuit, etc.

From the described it can be seen that any result of the process of determining the labels (except for the result "Error") uniquely determines all the labels to the conclusions of the engine.

The form of visualization by the display unit of these results and other conditions of the device can be arbitrary and is determined by the block circuit design (indicators, alphanumeric, etc.) and the control action of the MC.

The device operates in accordance with the time diagram presented in figure 5. The entire cycle of its operation consists of three stages:

Battery Diagnostics;

The process of identifying tags;

Indication of the result of determination.

Battery Diagnostics. Immediately after turning on the device and initializing the MK, the device diagnoses the charge levels of both batteries using the ADC. This procedure eliminates the operation of the device in an unacceptable mode, prevents the appearance of incorrect results of the definition of labels.

The poles of battery 3 are constantly connected to the ADC. The poles of the battery 1 are connected to the ADC only at the time of measuring the value of its potential. This short-term connection is made by the switching key 6 under the control of MK. The use of two galvanically isolated batteries and the implementation of galvanic isolation between the MK and the bundle “battery 1 - disturbing motor winding” protects the MK from powerful induction interference that occurs there in the process of identifying labels.

MK through the ADC scans the battery potential levels and compares them with the maximum allowable. If the battery potentials are above these levels, the MK through the display unit reflects the status of "Ready", thereby informing the user that the diagnosis was successful and you can begin to determine the labels. Otherwise, an “Error” is displayed and the start of the tagging process is blocked.

After a successful diagnosis, the MK enters the standby mode of pressing the start button of the tag definition process.

The process of identifying tags.

The process of determining the prototype marks involves four separate measurements: measurements in the direct (figure 3a) and reverse polarity (figure 3b) first for the “B” winding, then in the direct (figure 3c) and reverse polarity (figure 3d) for the “C” winding .

In the proposed device, the analogue of a measuring DC voltmeter is an ADC. Due to the multi-channel ADC, the process of determining tags in the device is optimized and contains only two measurements. The first measurement in direct polarity for two windings “B” and “C” at once, and the second in reverse polarity also for the same windings. The change in polarity of the ADC inputs to the terminals of the windings "B" and "C" is carried out by the switching key 5, which is enough for two states.

After pressing the button, the process of identifying marks starts. It begins with the fact that the MK instructs the display unit to visualize the status of "The process is in progress." This state is reflected by the indication until the device generates the final result of the definition of labels.

In the initial state, the switching key 4 closes the conclusions of the "disturbing" motor winding between each other, and the switching key 5 holds ready for the measurement circuit in direct polarity. To ensure the first measurement in direct polarity, the switch key 5 remains in its original state. MK sends a signal to the switching key 4, which simultaneously opens the terminals of the “disturbing” winding and connects the positive potential of the battery 1 to the terminal of the motor winding “An”, thereby forming a “disturbing” current pulse (leading edge) in it.

Immediately after the initiation of a "disturbing" pulse, the ADC scans and remembers the potentials of the induction "echo" at the terminals of the windings "B" and "C" (figure 6). By scanning here is meant a series of interval measurements in a limited time range.

After the scan is completed, the battery 1 is disconnected from the winding "A". The findings of the “disturbing” motor winding again close together. The first measurement is completed. Between the first and second measurements, the MK pauses so that the resonant induction oscillations in the “disturbing” motor winding are quieted down. Closing the terminals of the "disturbing" motor winding in the initial state of the switching key 4 also contributes to this process.

After a pause, the second measurement begins. To provide a second measurement, the MK switches the switch key 5 to an alternative state. Further, everything is repeated by analogy with the first measurement. A “disturbing” impulse in the “A” winding is initiated. The ADC scans the induction "echo" at the terminals of the windings "B" and "C". Battery 1 is disconnected from winding "A".

After the completion of two measurements, MK begins the analysis of the four results.

The analysis algorithm is two-stage. At the first stage, MK divides the results into positive and negative by the criterion of detecting an induction “echo” in them. A positive result is understood as one in which the MK detected an induction "echo" in the winding, i.e. recorded a group of consecutive measurements with an amplitude above zero (figure 6 a). And, on the contrary, a negative result means one in which the induction "echo" in the winding is not detected, i.e. the amplitude of the recorded measurements is equal to zero (figure 6 b). The positive result is assigned the value - 1, the negative - 0. The result of the first stage of the analysis is a string consisting of four binary numbers.

At the second stage of the analysis, MK compares this line with the possible options from Table 1 below, and coincidentally forms the final result of the label definition.

Table 1

Combination Option No.
results Winding "B" Winding "C" Label Definition Summary Direct polarity measurement Reverse Polarity Measurement Direct polarity measurement Reverse Polar Measurement
nosti 0 0 0 0 Mistake 0 0 0 one Mistake 0 0 one 0 Mistake 0 0 one one Mistake 0 one 0 0 Mistake 0 one 0 one Change the labels in the winding "A" 0 one one 0 Change the labels in the winding "B" 0 one one one Mistake one 0 0 0 Mistake one 0 0 one Change the labels in the winding "C" one 0 one 0 Full match tags one 0 one one Mistake one one 0 0 Mistake one one 0 one Mistake one one one 0 Mistake one one one one Mistake

This table reflects the following logical settings:

If in any of the windings “B” or “C” no “echo” is detected in the measurements of both polarities, then the process of determining the marks is erroneous (options No.: 1, 2, 3, 4, 5, 9, 13).

If an echo is detected in either of the windings “B” or “C” in the measurements of both polarities, then the process of determining the marks is erroneous (options No.: 4, 8, 12, 14, 16).

If both windings “B” and “C” are not consistent with winding “A”, then winding “A” is “accused” of the inconsistency, and the labels are changed for it (option No. 6).

This completes the tagging process.

Indication of the result of the definition of labels.

MK issues a command to the display unit to change the state "Process is in progress" to the state corresponding to the received measurement result. Visualization by the display unit of this state serves as a visual aid to the user in order to carry out the work of bringing the pin labels of the engine in order. Upon completion of this work, the device turns off.

This block diagram of the device allows for various variants of circuit implementation. The figure 7 presents a schematic diagram of a really working device in the embodiment when the switching keys are implemented on relay modules with optocoupler isolation, the display unit is implemented using LED indicators, and 1.5V (B1) and 9V (B2) power batteries are used.

A design variant of the device for this circuit implementation is presented in figure 8.

Visualization of the states of this circuit version of the device has the following features. The status "Change marks in the winding" is reflected by the flashing of the corresponding LED at the contact block. The status “Full coincidence of marks” is reflected by the flashing of all three LEDs at the contact block. The blinking of the “Error” LED has a different semantic load, depending on what stage of the device operation it appeared (immediately after turning on the device or after the process of determining labels).

The achievement of the claimed technical result contributes to the combination of the following essential features:

1. Use in the device MK. This made it possible to exclude the user from the process of identifying labels as a control and analyzing link, and to present the process of identifying labels in one step. This is implemented by automating the control of executive units and combining time-spaced measurement steps into an end-to-end continuous process.

2. The use in the device of the contact block and the switching key for measuring the induction “echo”. This made it possible to exclude the user from the process of identifying labels as a link in preparing measurement schemes, due to the canalization of motor leads to switching keys and creating the ability to prepare measurement schemes by automatic means.

As a result, the use of these two essential features made it possible to position the device as a self-sufficient device capable of performing the turnkey task.

3. The use of multi-channel ADCs allowed to increase the speed of the device, reducing the number of measurements from 4 to 2, and to simplify the device switch key 5, making it sufficient two states.

4. The use of MK with ADC allowed to ensure the compactness and portability of the device. Firstly, this is due to the compact design of the MK itself. Secondly, the compactness of the device is facilitated by the sensitivity of the ADC, which eliminates the need to have a bulky powerful “disturbing” battery in the device to reproduce the captured induction “echo”. The same factor made it possible to expand the scope of the device to powerful engines, in which the induction “echo” weakens with increasing power.

5. The use of galvanic energy for the needs of the functioning of the device. This allowed us to make the device autonomous in terms of power supply.

6. Separation of the device’s energy source into two galvanically isolated sources: battery 1 and battery 2. This made it possible to increase the noise immunity of the device, protecting it from inductive interference of the engine.

7. Using the device optimized way to visualize the results of the definition of labels. With this method, the contact marks of the contact block to which they are attached extend to the outputs of the motor windings, and the final display informs only of deviations from this template. This simplifies the technical implementation of the display, reducing the number of conditions required for visualization, and increases the user experience with the device.

8. Using the battery diagnostic tool. This eliminates the operation of the device in an unacceptable mode, prevents the appearance of incorrect results, increasing the reliability of the definition of labels.

Claims (10)

A device for determining the labels "start" and "end" of the windings of a three-phase asynchronous AC motor with a squirrel-cage rotor, containing a power battery (galvanic cell), characterized in that it further comprises programmable microcontroller (MK) with integrated multi-channel analog-to-digital converter (ADC) and control inputs / outputs; switching key for generating a current pulse; switching key for measuring the induction response; diagnostic switch key; indication unit; start button for the process of determining labels; contact block; battery power; moreover, three control outputs of the MC are connected to the control inputs of the switching key for generating the differential current, the switching key of the preparation of measurements, the switching key of diagnostics, the group of control outputs of the MK is connected to the control inputs of the display unit, one control input of the MK is connected to the start button of the label determination process, to the ADC inputs connected the positive output of the battery, the output of the diagnostic switch key, four outputs of the measurement preparation switch key, to the switching input of the diagnostic key are connected to the positive and negative poles of the power battery, the positive pole of the power battery is also connected to the input of the switching key for generating a differential current, the negative pole of the power battery is also connected to the contact "end" of the first pair of contact block, one output of the switching key for generating the differential current is connected to contact "start" of the first pair of contact block, the second output of the switching key of the formation of the differential current is connected to contact "end" of the first pair of block and the contacts, the four outputs of the second and third pairs of the block of contacts are connected to the inputs of the switching key of the preparation of measurements.

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