RU192269U1 - Microcontroller device for diagnostics of inter-turn insulation of an electric motor winding with a megohmmeter function - Google Patents

Abstract

The utility model relates to the field of electrical engineering, in particular to devices for diagnosing insulation of an electric motor characterized by its breakdown voltage, and can be used to build diagnostic tools for all types of insulation of an electric motor: inter-turn, inter-winding, between a winding and a housing, as well as measuring insulation resistance. Effect: expanding functionality by measuring using computing resources of a computer. SUBSTANCE: device contains a microcontroller, a voltage divider, a digital-to-analog converter, a first controlled key, an indicator, a constant voltage source, a second key, an exemplary inductance, a USART / USB interface converter. Moreover, the USART module of the microcontroller is connected to the USART / USB interface converter, configured to connect to the USB interface of the computer. 1 ill.

Description

The technical field to which the utility model relates.

The utility model relates to the field of electrical engineering, in particular to devices for diagnosing insulation of an electric motor, characterized by its breakdown voltage, and can be used to build diagnostic tools for all types of insulation of an electric motor: inter-turn, inter-winding, between a winding and a housing, as well as measuring insulation resistance.

State of the art

As a result of aging of the insulation of the winding of an induction motor, its breakdown voltage and resistance are reduced, which in turn leads to a sudden failure of the motor. To timely prevent damage to the insulation, its diagnosis is necessary, i.e. quality control (condition) of interturn isolation.

A microprocessor-based device for diagnosing insulation of an electric motor by self-induction EMF with a megohmmeter function (patent RU 2645499 C1, IPC G01R 27/26, G01R 31/34 of 11/23/2016) containing a microcontroller including a pulse-width modulator (PWM) and an analog comparator voltage divider , controlled reference voltage source, first controlled key, USART / USB interface converter, constant voltage source, diagnosed electric motor winding, second key, standard inductance, semiconductor diode, condensate and the computer.

The reference voltage source used in this device, controlled by a pulse-width modulator (PWM) of the microcontroller, is characterized by an increased noise level in the output signal. The presence of which is due, first of all, to the ripple of the output voltage of the low-pass filter, which is necessarily used as part of the reference voltage source (AVR131: Using the AVR's High-speed PWM. Access mode: http://www.gaw.ru/pdf/Atmel/app /avr/AVR131.pdf).

At the same time, for the normal functioning of the reference voltage source, continuous generation of PWM signals is necessary, accompanied by sharp jumps in current consumption by the digital part of the microcontroller, which in turn leads to a decrease in the sensitivity of the analog comparator of the microcontroller, due to the formation of additional noise in the power circuit of the analog part of the microcontroller ( Ryumik S.M. 1000 and one microcontroller circuit Issue 1 / S.M. Ryumik - M .: Dodeka-XXI Publishing House, 2010. - 356 p., P. 39.), which means it leads to an increase the error of diagnostics of the insulation of the winding of an induction motor.

The disadvantage of this device is the low accuracy of diagnosis of insulation of the motor.

The closest analogue - a prototype to the claimed technical solution is a microcontroller device for diagnosing inter-turn insulation of an electric motor winding with a megohmmeter function (patent RU 184404, G01R 31/06, G01R 27/02, application form 13.03.2018) containing a microcontroller including a data register and an analog comparator, voltage divider, digital-to-analog converter (DAC), the first controlled key, indicator, constant voltage source, second key, exemplary inductance, semiconductor diode, capacitor, while: the second you The water supply of the DC voltage source is connected to the first terminals of the diagnosed motor winding and the model inductance, the second terminals of which are connected to the second terminal of the second key, which can either be in the "lower" position - the diagnosed motor winding is connected, or in the "upper" position - the model inductance is connected and the anode of a semiconductor diode, the cathode of which is connected to the first capacitor plate; the first terminal of the second switch is connected to the second terminal of the first managed key and to the second terminal terminal of the voltage divider; the first extreme terminal of the voltage divider is connected to the first terminals of the DC voltage source and the first controlled key, as well as to the second capacitor lining; the control output of the first key is connected to the microcontroller; the middle output of the voltage divider is connected to the second input of the analog comparator of the microcontroller; the indicator is connected to the microcontroller by means of the group of outputs of the corresponding port of the microcontroller; DAC control inputs are connected to the outputs of the microcontroller data register by means of the outputs of the corresponding microcontroller port; the DAC output is connected to the first input of the analog comparator of the microcontroller.

A disadvantage of the known solution is the limited functionality due to the design features of the microcontroller, consisting in the limited processor power and memory size, which does not allow archiving of measurement results, their output in the form of graphs, comparison of the data with reference samples.

Utility Model Disclosure

The technical result that can be achieved using the proposed utility model is to expand its functionality by conducting measurements using computer computing resources.

The technical result is achieved by the fact that in the microcontroller diagnostic device for inter-turn insulation of the motor winding with a megohmmeter function, the microcontroller includes a data register and an analog comparator, a voltage divider, a digital-to-analog converter (DAC), the first controlled key, a constant voltage source, the second key, an exemplary inductance, semiconductor diode, capacitor, wherein: the second terminal of the DC voltage source is connected to the first terminals of the diagnosed winding an electric motor and a model inductance, the second terminals of which are connected to the second terminal of the second key, which can either be in the "lower" position - the diagnosed motor winding is connected, or in the "upper" position - the model inductance and the anode of the semiconductor diode are connected, the cathode of which is connected to the first capacitor plate; the first terminal of the second switch is connected to the second terminal of the first managed key and to the second terminal terminal of the voltage divider; the first extreme terminal of the voltage divider is connected to the first terminals of the DC voltage source and the first controlled key, as well as to the second capacitor lining; the control output of the first key is connected to the microcontroller; the middle output of the voltage divider is connected to the second input of the analog comparator of the microcontroller; DAC control inputs are connected to the outputs of the microcontroller data register through the outputs of the corresponding microcontroller port; the DAC output is connected to the first input of the analog comparator of the microcontroller, the USART / USB interface converter is introduced, and the USART microcontroller module is connected to the specified USART / USB interface converter, configured to connect to the USB interface of the computer.

Brief Description of the Drawings

In FIG. presents a structural diagram of a microcontroller device for diagnosing inter-turn insulation of an electric motor winding with a megohmmeter function.

Utility Model Implementation

A microcontroller device for diagnosing interturn insulation of an electric motor winding with a megohmmeter function contains (Fig.) A microcontroller 1 including a data register (not shown in FIG.), An analog comparator (not shown in FIG.) And a USART module (not shown in FIG.), A voltage divider 2, digital-to-analog converter (DAC) 3, the first controlled key 4, the converter of USART / USB 5 interfaces, a constant voltage source 6, the second key 7, the model inductance 8, the semiconductor diode 9, the capacitor 10, the computer 11, while: the second output DC voltage source 6 is connected to the first terminals of the diagnosed motor winding 12 and exemplary inductance 8, the second terminals of which are connected to the second terminal of the second switch 7, which can either be in the “lower” position - the diagnosed motor winding 12 is connected, or in the “upper” position - connect the model inductance 8 and the anode of the semiconductor diode 9, the cathode of which is connected to the first lining of the capacitor 10; the first terminal of the second switch 7 is connected to the second terminal of the first managed switch 4 and the second extreme terminal of the voltage divider 2; the first extreme terminal of the voltage divider 2 is connected to the first terminals of the DC voltage source 6 and the first managed switch 4, as well as with the second lining of the capacitor 10; the control output of the first key 4 is connected to the microcontroller 1; the average output of the voltage divider 2 is connected to the second input of the analog comparator (not shown in Fig.) of the microcontroller 1; the control inputs of the DAC 3 are connected to the outputs of the data register of the microcontroller 1 (not shown in Fig.) by means of the outputs of the corresponding port of the microcontroller 1; the output of the DAC 3 is connected to the first input of the analog comparator (not shown in Fig.) of the microcontroller 1; the USART module of microcontroller 1 is connected to the USART / USB 5 interface converter, which is connected to the USB interface of computer 11.

A microcontroller device for diagnosing interturn insulation of an electric motor winding with a megohmmeter function works as follows.

Key 7 is in the “upper” position, i.e. reference inductance 8 is included.

The microcontroller 1 sets the output level of the DAC 3 the specified level of the reference voltage and closes the controlled key 4. The voltage at the output of the DAC 3 is set in accordance with the code from the data register of the microcontroller 1 to the control inputs of the DAC 3.

As a result of the closure of the key 4, along the circuit: the second output of the constant voltage source 6, model inductance 8, key 7, key 4, the first output of the constant voltage source 6, an increasing current flows. At some point, the microcontroller 1 opens the key 4, the self-induction EMF appears on the terminals of the model inductance 8, which is applied to the voltage divider 2. If the voltage at the middle terminal of the divider 2 exceeds the reference voltage, then the analog comparator of the microcontroller 1 will change the logic level at the output. On this signal, the microcontroller 1 estimates the amplitude value of the self-induction EMF. In model inductance 8, there are no defects in the inter-turn isolation, and the value of the self-induction EMF will be maximum. This value is stored by microcontroller 1.

Next, the key 7 is transferred to the "lower" position, i.e. the diagnosed winding 12 of the electric motor is connected. According to the circuit: the second output of the constant voltage source 6, the diagnosed winding 12 of the electric motor, key 7, key 4, the first output of the constant voltage source 6 flows increasing current. At some point, the microcontroller 1 opens the key 4, the self-induction EMF appears on the terminals of the diagnosed motor winding 12, which is applied to the voltage divider 2. If the inter-turn insulation of the diagnosed motor winding 12 contains defects that reduce the breakdown voltage and also has low resistance, then part of the energy stored in its inductance after opening the key 4 will be dissipated in the form of heat on the resistance of the inter-turn insulation. In this case, the self-induction EMF will be lower than the value set using the model inductance, and the analog comparator of the microcontroller 1 will not change the logic level at the output.

Then, the microcontroller 1 proceeds to the next cycle of measuring the amplitude of the self-induction EMF. The microcontroller 1 reduces the voltage at the output of the DAC 3 and closes the key 4 again, the cycle is repeated until the microcontroller 1 determines the value of the amplitude of the self-induction EMF. By the value of the amplitude of the EMF of self-induction, an assessment is made of the state of isolation.

The implementation of the megohmmeter function is as follows.

The controlled insulation resistance between the motor windings or between the winding and the casing is connected to the plates of the capacitor 10 (the controlled resistance is not shown in Fig.). The second key 7 is in the "upper" position, i.e. the inductance 8 is turned on. The microcontroller 1 periodically closes / opens the key 4, the self-induction EMF pulses appear on the terminals of the inductance 8, which is applied to the voltage divider 2, as well as to the anode of the semiconductor diode 9 and to the second lining of the capacitor 10. The capacitor 10 is charged positive impulses EMF self-induction to a certain value. If the controlled insulation resistance to which the voltage of the capacitor 10 is applied is high, then the voltage of the capacitor 10 will be equal to the maximum amplitude value of the self-induction EMF pulses. The microcontroller 1 fixes this voltage value using the previously described sequence for measuring the self-induction EMF. If the controlled insulation resistance to which the voltage of the capacitor 10 is applied is low, the voltage of the capacitor 10 will also be low. Thus, the voltage across the capacitor 10 applied to the controlled insulation will be determined by the resistance value of the controlled insulation. Since the microcontroller 1 measures the voltage across the capacitor 10, then, in a certain sequence, the microcontroller 1 determines the resistance value of the controlled insulation, thus, the megohmmeter function is implemented.

Microcontroller 1 sends the pre-processed measurement results through the USART / USB 5 interface converter to computer 11, in which new functions can be implemented, for example, archiving measurement results and displaying them in graphical form on a monitor, comparison with reference samples or their models, as well as data transfer to a remote computer via the Internet.

The developed device in comparison with the prototype and other known solutions has the advantage of expanding the functionality of a microprocessor-based device for diagnosing electric motor insulation by self-induction EMF with a megohmmeter function by performing measurements using computer computing resources.

Claims (1)

A microcontroller device for diagnosing interturn isolation of an electric motor winding with a megohmmeter function is configured to transmit a signal to a computer using a USART / USB interface converter, containing a microcontroller, a voltage divider, a digital-to-analog converter (DAC), a first controlled key, a constant voltage source, and a second key, exemplary inductance, semiconductor diode, capacitor, while the second terminal of the DC voltage source is connected to the first terminals of the diagnosed ohm motor and model inductance ramps, the second terminals of which are connected to the second terminal of the second key, which can either be in the “lower” position — the diagnosed motor winding is connected, or in the “upper” position — the model inductance and the anode of the semiconductor diode are connected, the cathode of which is connected to the first lining of the capacitor; the first terminal of the second switch is connected to the second terminal of the first managed key and to the second terminal terminal of the voltage divider; the first extreme terminal of the voltage divider is connected to the first terminals of the DC voltage source and the first controlled key, as well as to the second capacitor lining; the control output of the first key is connected to the microcontroller; the middle output of the voltage divider is connected to the second input of the analog comparator of the microcontroller; DAC control inputs are connected to the outputs of the microcontroller data register through the outputs of the corresponding microcontroller port; the DAC output is connected to the first input of the analog comparator of the microcontroller, characterized in that the microcontroller is equipped with a USART module, and a USART / USB interface converter is additionally inserted into the device, and the USART microcontroller module is connected to the specified USART / USB interface converter, configured to connect to the USB interface a computer.

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