CN113067310A - Motor fault detection and protection device - Google Patents
Motor fault detection and protection device Download PDFInfo
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- H—ELECTRICITY
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Abstract
The invention discloses a motor fault detection and protection device, which comprises a voltage current collector and a motor work monitoring device, wherein the voltage current collector comprises a voltage current collector and a motor work monitoring device; in the voltage and current collector, a signal collecting and converting module collects current and voltage signals of a three-phase motor and converts the current and voltage signals into small voltage signals to be sent to a digital-to-analog conversion module for digital-to-analog conversion, and a microcontroller performs data processing analysis and fault judgment and controls a relay protection circuit module and a fault indication module to perform protection and alarm; the display module displays the working parameters and the state of the motor; the key module sets rated parameters and fault protection action time of the motor; the motor working monitoring equipment monitors motor parameters and states in real time, and sets rated parameters and fault protection action time of a protected motor; the motor work monitoring equipment is in data transmission with the voltage and current collector through the communication module. The invention can realize remote transmission of data without being limited by any distance, improves the maintenance efficiency and also leads to the comprehensive intellectualization of the industry.
Description
Technical Field
The invention belongs to the technical field of motor fault detection and protection, and particularly relates to a motor fault detection and protection device.
Background
In practical engineering application, the severe working environment and the lack of daily maintenance often easily cause the fault and even damage of the motor, and great influence and loss are caused to industrial production and life of people. Therefore, the realization of real-time monitoring, fault judgment and timely removal of the motor is the premise of ensuring safe and reliable operation of the motor.
In the early days, protection of motors was mainly performed by mechanical protection devices such as fuses, bimetal thermal relays, automatic switches for motor protection, and electromagnetic relays. The fuse is a fuse which fuses due to self heat when the current is larger than a certain value, so that a loop is broken, and the motor stops running. The fuse is simple and convenient to install, low in price, but few in function, and cannot play a role in protection when the motor has faults such as overload caused by faults and the like. When the fuse is used to protect the three-phase asynchronous motor, if the fuse of one phase is disconnected due to an excessive current, the three-phase asynchronous motor is disconnected, which causes a series of accidents and losses.
The working principle of the thermal relay is based on the thermal effect of the bimetallic strip: the bimetallic strip is formed by integrating a pair of metal sheets, and the expansion coefficients of the metal sheets are different. When current flows, the generated thermal effect can cause the bimetallic strip to bend towards the side with smaller expansion coefficient, and the current value is in direct proportion to the bending degree. When the current is larger than the setting current value by a certain multiple, the tripping device can be actuated, and then the main circuit is disconnected, thereby realizing the protection function of the main circuit. The thermal relay motor protector has the advantages of simple structure, convenient operation, low price and the like, and has the inverse time limit characteristic. Therefore, it is widely used for overload protection of motors. However, the application of thermal relays to the field of motor protection has certain limitations: the protective characteristics of the thermal relay have certain dispersibility, the stability is low, and the thermal relay is easily influenced by surrounding environment factors, such as great requirements on environment temperature, mechanical vibration and the like; the repeatability is poor, and the motor can not be well protected under the conditions of frequent starting, heavy load starting, multiple short-time overload and the like; and thirdly, the function is single, and faults, short-circuit faults and the like in the starting process of the motor cannot be effectively protected. When the motor is slightly overloaded, the temperature is too high due to the heat accumulation generated by the winding, but the temperature of the motor winding cannot be directly detected, so that the situation cannot be effectively protected.
At present, a conventional 8/16 bit single chip machine is widely used for electrical protection. But they have only basic data acquisition and control functions, have limited capabilities in man-machine interaction, data query, remote connection, etc., and lack the necessary network communication functions. If network communication and intelligent remote control are added into motor protection, unexpected effects can be brought to the motor protection, large-scale equipment damage conditions are greatly avoided, and a large amount of cost is saved.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a motor fault detection and protection device for overcoming the defects of the prior art.
In order to achieve the technical purpose, the technical scheme adopted by the invention is as follows:
a motor fault detection and protection device comprises a voltage current collector and a motor work monitoring device;
the voltage and current collector comprises a microcontroller, a signal collecting and converting module, a digital-to-analog conversion module, a display module, a relay protection circuit module, a fault indication module, a key module and a communication module;
the signal acquisition and conversion module acquires current and voltage signals of the three-phase motor, converts the current and voltage signals into small voltage signals and sends the small voltage signals to the digital-to-analog conversion module for digital-to-analog conversion;
the digital signal converted and output by the digital-to-analog conversion module enters a microcontroller for data processing analysis and fault judgment, and when the fault of the motor is diagnosed and the protection time is up, the microcontroller controls a relay protection circuit module and a fault indication module to carry out protection and alarm;
the display module displays the working parameters and the state of the motor in real time;
the key module is used for setting rated parameters and fault protection action time of motors of different models;
the motor work monitoring equipment is used for monitoring rated parameters of the motor and current, voltage, power and state under the current work in real time; setting rated parameters and fault protection action time of the protected motor;
the motor work monitoring equipment is in data transmission with the voltage and current collector through the communication module.
In order to optimize the technical scheme, the specific measures adopted further comprise:
the microprocessor is STM32F103C8T6, and the digital-to-analog conversion module adopts MAX 187.
The communication module is a wireless communication module or a GSM mobile phone card; the wireless communication module selects ESP 8266.
The relay protection circuit module controls the on-off of a relay controlled by a photoelectric coupling device to control the power supply of the motor;
when the electric energy is too large or the power is too large, the microcontroller outputs a control signal to trip the motor and simultaneously sends out an alarm signal to avoid the motor from generating larger damage.
The voltage and current collector adopts I2The EEPROM of the communication C is used for storing the time, current and voltage parameters of the motor in failure, parameter setting can be realized, and the set parameters after power failure are stored in the external RAM without resetting.
The display module selects an LCD1602 liquid crystal screen to display rated parameters, working voltage and working current of the motor; and when the motor breaks down, fault information and protection action time are displayed.
The fault indication module is an LED light-emitting diode externally connected with the display module and is used as an indicator lamp for detecting voltage, current and communication state with an upper computer.
The communication module connects the motor work monitoring equipment and the voltage and current collector into a network system through the Ali cloud server to perform real-time monitoring and data transmission.
The microcontroller performs data processing analysis and fault judgment, and comprises:
fourier effective value calculation: filtering discrete and quantized sampling data by adopting an FFT butterfly algorithm and calculating an effective value of the working electric quantity of the motor;
phase detection: calculating the phase difference between each two phases of the three-phase current of the motor according to the discrete and quantized sampling data;
zero/negative sequence current component calculation: calculating zero and negative sequence components of the current according to a symmetrical component analysis method;
fault judgment and protection: analyzing the effective value, zero sequence electric quantity, negative sequence electric quantity and phase difference value of every two phases of the three-phase current, judging whether the motor has a fault, if so, distinguishing the attribution type of the fault, pulling up the starting flag bit of the corresponding fault protection program, and determining the specific fault type to match the corresponding protection measures according to the voltage and current parameters.
The protection measures are as follows:
overcurrent protection, namely analyzing and protecting data aiming at the symmetric fault;
negative sequence current protection, which is used for analyzing and protecting data aiming at non-ground faults in the asymmetric faults;
and zero sequence current protection, namely data analysis and protection are carried out on the ground fault in the asymmetric fault.
The invention has the following beneficial effects:
1. the motor protection device is based on a microcontroller, such as an STM32F103C8T6 controller of an ARM Cortex-M3 kernel, the motor is protected, a 12-bit ADC analog acquisition module programmable by the microcontroller is used for acquiring the voltage and the current of the motor during working, the corresponding power is calculated, the working state of the motor is detected in time, and if a fault occurs, a relay is triggered to power off the motor in time; an ESP8266 network is established, so that the data acquisition system can communicate with an upper computer conveniently, and the upper computer software displays acquired data and controls the interruption of a relay. When the parameters of the motor such as working current, voltage and the like exceed the specified range, the fault type is analyzed and judged, and the motor is protected in time.
2. The invention can replace the STM32 by other hardware processors with high-speed data acquisition capacity (such as FPGA, DSP, raspberry pie, and the like), and the upper computer communication can use the GSM mobile phone card to send the motor fault information to the mobile phone end in a short message manner besides using the wireless communication module to transmit AT instructions.
3. According to the invention, the FFT butterfly algorithm is applied to AC sampling, the Fourier analysis is applied to electrical analysis, and the AC signal of the motor can be rapidly discretized through the FFT butterfly algorithm, so that the data processing efficiency of the terminal is improved, and the damage of the motor caused by untimely tripping of a protection outlet due to untimely terminal data processing can be reduced.
4. According to the invention, the PC end and the mobile phone end software are utilized to realize high-efficiency management and control of the motor, a cloud server is constructed between the upper computer and the WIFI, so that remote transmission of data can be really realized without limitation of any distance, management and control personnel can issue instructions to the motor through the mobile phone APP and the computer client at any time and any place, even the motor in the whole production workshop can be subjected to combined management, the maintenance efficiency is improved, and meanwhile, the comprehensive intelligence of the industry is developed.
Drawings
FIG. 1 is a block diagram of the overall hardware module of the apparatus of the present invention;
FIG. 2 is a circuit diagram of a signal acquisition and conversion module in an embodiment;
FIG. 3 is a circuit diagram of an EEPROM AT24C02 memory in an embodiment;
FIG. 4 is a circuit diagram of the connection of an STM32 processor to an LCD1602 in an embodiment;
FIG. 5 is an illustration of the WEB interface effect in the embodiment;
FIG. 6 shows the operation mode of MQTT protocol in the embodiment;
FIG. 7 is a flow chart of the device procedure in the embodiment;
FIG. 8 is a flow chart of the radix-2 time decimation FFT algorithm in the embodiment
FIG. 9 is a diagram showing the overall design structure of the software system in the embodiment
FIG. 10 is a block diagram showing the structure of a motor failure response system in the embodiment
FIG. 11 is a logic flow diagram of the over-current protection in the embodiment
FIG. 12 is a logic flow diagram of negative sequence current protection in an embodiment
FIG. 13 is a logic flow diagram of zero sequence current protection in the embodiment
FIG. 14 is a working drawing of MQTT correctly sending messages in the embodiment
FIG. 15 is an example android port interface.
Detailed Description
Embodiments of the present invention are described in further detail below with reference to the accompanying drawings.
Referring to fig. 1, a motor fault detection and protection device includes a voltage current collector and a motor work monitoring apparatus;
the voltage and current collector comprises a microcontroller, a signal collecting and converting module, a digital-to-analog conversion module, a display module, a relay protection circuit module, a fault indication module, a key module and a communication module;
the signal acquisition and conversion module acquires current and voltage signals of the three-phase motor, converts the current and voltage signals into small voltage signals and sends the small voltage signals to the digital-to-analog conversion module for digital-to-analog conversion;
the digital signal converted and output by the digital-to-analog conversion module enters a microcontroller for data processing analysis and fault judgment, and when the fault of the motor is diagnosed and the protection time is up, the microcontroller controls a relay protection circuit module and a fault indication module to carry out protection and alarm;
the signal acquisition and conversion module is mainly used for acquiring parameters such as working voltage and working current of the motor, and the parameters are subjected to filtering, sampling and holding, and are processed by the digital-to-analog conversion module and then enter the microcontroller for data analysis. MAX187 of Meixin corporation can isolate and convert voltage signals and current signals of the motor, and the converted signals can be directly collected by an internal ADC channel of STM32F103C8T 6. The circuit diagram of the signal acquisition and conversion module is shown in fig. 2.
The display module displays the working parameters and the state of the motor in real time;
the key module is used for setting rated parameters and fault protection action time of motors of different models;
the motor work monitoring equipment is used for monitoring rated parameters of the motor and current, voltage, power and state under the current work in real time; setting rated parameters and fault protection action time of the protected motor;
the motor work monitoring equipment is in data transmission with the voltage and current collector through the communication module.
In an implementation, the microprocessor is STM32F103C8T6, and the digital-to-analog conversion module employs MAX 187.
The communication module is a wireless communication module or a GSM mobile phone card; the wireless communication module selects ESP 8266.
Generally, the operating voltage of the STM32 is 3.3V, the driving current is only ten or more mA, and when the operating voltage of the motor is 220V, the current can reach 5A-20A, and the difference between the voltage and the driving current is large.
Therefore, a relay protection circuit module is required to be added between the microcontroller and the signal acquisition conversion module, and the switch of the relay controlled by the photoelectric coupler is selected to control the motor power supply. When faults of overlarge electric energy, overlarge power and the like occur, the controller can output a control signal in time to enable the motor to trip, and meanwhile, an alarm signal is sent out to avoid the motor from being damaged more, namely, the relay protection circuit module controls the switch of a relay controlled by a photoelectric coupling device to achieve the control of a motor power supply;
when the electric energy is too large or the power is too large, the microcontroller outputs a control signal to trip the motor and simultaneously sends out an alarm signal to avoid the motor from generating larger damage.
In industry, generally, a plurality of motors can work simultaneously on one production line, and the progress of the whole production can be affected by whether the motors work normally, so that the machines on the whole production line need to be monitored. Therefore, the motor protection device and the monitoring center need to establish communication, and the ESP8266-01S is selected to realize signal transmission between the upper computer software and the motor.
Simultaneous voltage and current collector using2EEP for C communicationThe ROM is used for storing parameters of time, current and voltage when the motor fails, parameter setting can be realized, and the set parameters after power failure are stored in the external RAM without resetting. The block circuit of the EEPROM chip AT24C02 is shown in fig. 3.
The display module selects an LCD1602 liquid crystal screen to display rated parameters, working voltage and working current of the motor; and when the motor fails, the fault information and the protection action time are displayed
The fault indication module is an LED (light emitting diode) externally connected with the display module and is used as an indicator lamp for detecting voltage, current and communication state with an upper computer, so that detection personnel can conveniently handle faults and a good human-computer interface is established. Fig. 4 is a circuit diagram of the connection of the STM32 processor to the LCD 1602.
The communication module connects the motor work monitoring equipment and the voltage and current collector into a network system through the Ali cloud server to perform real-time monitoring and data transmission.
The microcontroller performs data processing analysis and fault judgment, and comprises:
fourier effective value calculation: filtering discrete and quantized sampling data by adopting an FFT butterfly algorithm and calculating an effective value of the working electric quantity of the motor;
phase detection: calculating the phase difference between each two phases of the three-phase current of the motor according to the discrete and quantized sampling data;
zero/negative sequence current component calculation: calculating zero and negative sequence components of the current according to a symmetrical component analysis method;
fault judgment and protection: analyzing the effective value, zero sequence electric quantity, negative sequence electric quantity and phase difference value of every two phases of the three-phase current, judging whether the motor has a fault, if so, distinguishing the attribution type of the fault, pulling up the starting flag bit of the corresponding fault protection program, and determining the specific fault type to match the corresponding protection measures according to the voltage and current parameters.
The functions are realized through an online monitoring software development module, an internet of things internal communication protocol development module and an embedded system software development module based on the Ali cloud server.
(1) Online monitoring software based on Ali cloud server
The PC client end written and designed based on Python language remotely transmits a new protection fixed value and a motor rated parameter to the protection device through the Ali cloud server, and receives protection action parameters (action time, action value, action name and the like) transmitted by the protection device.
The top of the interface needs to be provided with a static IP address configuration for the Ali cloud, a data receiving and displaying window is arranged below the Ali cloud, and data uploaded to the cloud end by the microcontroller are displayed on the window; and plug-ins for sending commands and a data sending display window are also required to be installed, and command characters sent to the microprocessor by the client are mainly displayed. The interface effect diagram is shown in fig. 5.
(2) Internet of things internal communication protocol development module
WiFi remote control is achieved, and Ariicloud is selected as a data transfer platform. The Aliyun Internet of things platform provides safe and reliable connection communication capacity for equipment, is downwards connected with mass equipment, and supports equipment data acquisition and cloud-up;
and a cloud API is provided upwards, and the instruction data is issued to the equipment end through API calling to realize remote control. The Aliyun provides the SDK of the equipment end with multiple protocols such as MQTT, CoAP, HTTP/S and the like, so that the real-time requirement of long connection is met, and the low-power-consumption requirement of short connection is also met. Since the microprocessor STM32 has a small amount of data to transmit and the WiFi module has limited transmission capabilities, we chose the MQTT protocol to transmit data. The MQTT protocol operating mode is shown in fig. 6.
(3) Embedded system software development module
Firstly, a system program is set up to carry out A/D sampling, whether the motor works normally is judged, and if the motor works normally, a motor protection subprogram is started. Under the condition that the motor normally operates and the relay module is not triggered, the working parameters of the motor can be checked through the keys; when the motor breaks down, the driving code of the motor protection system is executed, the fault information is stored, and the indicator light gives an alarm. The overall program structure of the apparatus is shown in fig. 7.
The fourier effective value calculation described above: filtering discrete and quantized sampling data by adopting an FFT butterfly algorithm and calculating an effective value of the working electrical quantity of the motor, and analyzing as follows:
root mean square method
If U is equal to Umsinwt, wherein
Discretizing to obtain
Where N is the number of equally spaced samples per cycle, ukIs sampled for the kth time
From the sampling theorem, such an algorithm can take into account
Subharmonic wave
In the same way
By
Discretization can obtain
Wherein, P is active power, Q is reactive power, S is apparent power, T is sampling period value, and phi is the phase difference between the voltage and the current at the current moment.
② FFT butterfly algorithm
Discrete Fourier Transform (DFT) is often used in digital signal processing to obtain the frequency domain characteristics of a signal. Although the traditional DFT algorithm can obtain the frequency domain characteristics of the signal, the algorithm has large calculation amount and long time consumption, and is not beneficial to the real-time signal processing of a computer. Therefore, the DFT cannot be applied to the actual engineering project for a long time since the discovery, and the discrete fourier transform is not widely applied to the actual engineering until a fast discrete fourier computing method, FFT, is discovered. It should be emphasized that FFT is not a new frequency domain feature acquisition method, but a fast implementation algorithm of DFT.
Alternating current sampling based on FFT butterfly algorithm
The motor protection carries out mathematical operation and logical operation according to discrete and quantized sampling data which are provided by a data acquisition system and reflect the electric quantity of a protected motor, rapidly and unmistakably judges the fault type, and realizes various fault protection functions, so that the accuracy of the sampling data directly influences the accuracy of fault judgment; the selection of an alternating current sampling algorithm with high precision and high speed has important significance for improving the accuracy and timeliness of fault judgment. Among many ac sampling algorithms, the fourier series recursive algorithm is most representative in motor protection. A flow diagram of the radix-2 time decimation FFT algorithm is shown in fig. 8.
The basic idea of the Fourier algorithm is that the periodic signal f (t) is a periodic time function which, besides the fundamental wave, contains non-attenuated DC components and harmonics, and can be decomposed into
f(t)＝f0+f1(t)+f2(t)+…+fn(t)+… (2)
In the formula (f)0Is a direct current component; f. ofnAnd (t) is n-th harmonic, and n is a natural number. For the n-th harmonic can be expressed again as
fn(t)＝an cos(nΩt)+bn sin(nΩt) (3)
In the formula, omega is angular frequency; a isn、bnRespectively sine component and cosine component coefficients of the nth harmonic. Is expressed as
Discretizing the formulas (3) and (4), writing the discretized formulas into the following forms
Wherein N is the number of sampling points, and f (k) is the k-th sampling value. By substituting formula (2) for formula (1), then
The above formula shows that the amplitudes of the harmonics of a periodic function f (t) are respectively anAnd bnThe sum of the sine and cosine terms of (c). Can pass through anAnd bnCalculating amplitude A of n-th harmonicnAnd phase psin
In the motor protection system, the sine component of the fundamental wave of the working current and voltage of the motor can be obtained by the formula (5) and the formula (6)
And cosine component
Thereby obtaining the active power, the reactive power and the apparent power of the fundamental wave
In summary, the software and hardware system for detecting and protecting the motor fault of the intelligent digital electric meter provided by the invention is as follows:
(1) hardware System architecture
The motor protector mainly analyzes and judges the fault type when the working current, voltage and other parameters of the motor exceed the specified range, and protects the motor in time. The overall hardware structure of the motor protector designed by the invention is shown in figure 1 and mainly comprises a controller, a signal conversion module, a digital-to-analog conversion module, a man-machine interaction module, a wireless communication module and the like. The signal conversion module converts current and voltage signals of the three-phase motor into small voltage signals and sends the small voltage signals to MAX187 for digital-to-analog conversion, the converted and output digital signals enter STM32 for data processing analysis and fault judgment, and when the motor is diagnosed to have faults and the protection time is up, the controller controls the trip of the protection outlet and the alarm circuit to protect and alarm; meanwhile, working parameters, states and the like of the motors can be displayed on the liquid crystal display screen in real time, and rated parameters and fault protection action time of the motors of different models can be set through the keys. In addition, the wireless communication module connects the developed mobile phone APP, the computer client and the motor protection device into a network system through the Ali cloud server to perform real-time monitoring and data transmission.
(2) Software System Overall design
The software part of the motor protection system mainly comprises a fault protection program based on a microprocessor STM32F103C8T6 and a computer client development program for communication. The fault protection program mainly comprises 8 submodules, including an AD conversion control module, a Fourier effective value calculation module, a phase detection module, a zero/negative sequence current component calculation module, a fault judgment module, a serial port data transceiver module, a key parameter setting module and a liquid crystal display control module. A block diagram 9 of a system software design structure of the motor protection device is shown.
AD conversion control: controlling MAX187, and converting voltage and current of the three-phase motor from analog signals into digital signals;
calculating Fourier effective value: performing software filtering on discrete and quantized sampling data by adopting an FFT butterfly algorithm and calculating an effective value of the working electric quantity of the motor;
③ detecting the phase: calculating the phase difference between each two phases of the three-phase current of the motor according to the discrete and quantized sampling data;
and fourthly, calculating a zero/negative sequence current component: calculating zero and negative sequence components of the current according to a symmetrical component analysis method;
fault judgment/protection: judging whether the motor has a fault according to whether overcurrent or zero and negative current components exist; the symmetrical faults take overcurrent as a judgment basis, the non-ground faults in the asymmetrical faults take negative sequence current as a judgment basis, and the ground faults in the asymmetrical faults take zero sequence current as a judgment basis;
setting key parameters: detecting whether a key is pressed down or not, and setting parameters (such as rated current, voltage and the like) and fault protection action time of the motor;
seventh, liquid crystal display control: controlling the display of a liquid crystal display screen, and mainly displaying rated parameters, working voltage and working current of a motor; when the motor fails, fault information and protection action time are displayed;
transmitting and receiving data by the serial port: and data receiving and sending are completed, so that the protection device, the mobile phone APP and the computer client can realize remote data transmission through the Ali cloud server.
Ninthly, the client application program: the method mainly realizes two functions, namely monitoring and checking rated parameters of the motor and current, voltage, power, state and the like under the current work; and the second function is system parameter setting, which mainly sets the rated parameters and the fault protection action time of the protected motor.
Judging and protecting motor faults: the response of the fault judging and protecting system of the motor is analyzed and judged according to the effective value, the zero sequence electric quantity, the negative sequence electric quantity and the phase difference value of each two phases of the output three-phase current so as to realize fault protection.
The system is based on zero and negative sequence current components and three-phase current effective values
And judging whether the motor fails, if so, classifying the general attribution type of the failure, and pulling up the starting flag bit of the corresponding failure protection program. The set values of the zero and negative sequence current components are respectively I0、I-Indicating, for the current rating of the motor to be protected, IeAs shown, the flow chart of the structure is shown in FIG. 10.
The general attribution type of the fault needs to be subdivided after being judged, and the specific fault type is determined according to the measured voltage and current parameters to match corresponding protective measures.
Over-current protection
The overcurrent protection mainly analyzes and judges data aiming at symmetrical faults (mainly comprising short circuit, locked rotor and overload); and setting a starting flag bit of the pull-up over-current protection module as over _ st, and starting the module to work. The fault delay time is t, and the protection action set values of short circuit and locked rotor are I respectivelydl、IdzThe delay time setting values of short circuit and locked rotor are respectively Tdl、TdzThe corresponding logical structure diagram is shown in fig. 11.
Protection of negative sequence current
The negative sequence current protection mainly aims at analyzing and protecting data of non-ground faults (mainly comprising phase failure, interphase short circuit and three-phase imbalance) in the asymmetric faults. When the starting flag bit neg _ st of the negative sequence current protection module is pulled high, the module starts to work. The delay time setting values of the reverse phase, the open phase, the three-phase imbalance and the interphase short circuit are respectively Tnx、Tdx、Tbph、TxjdlThe logical structure flow chart is shown in fig. 12.
② zero sequence current protection
Main needle of zero sequence current protection systemAnd analyzing and processing data of the ground faults (mainly comprising single-phase grounding and two-phase grounding) in the asymmetric faults. When the starting zone bit zero _ st of the zero sequence current protection module is pulled high, the module starts to work. The delay time setting values of the single-phase grounding and the two-phase grounding are respectively Tdx、TlxThe zero sequence current protection logic structure diagram is shown in fig. 13.
(3) Server application design
According to the project, an Android mobile phone and a PC client are used as upper computers, a new protection constant value and a motor rated parameter are remotely transmitted to a protection device through the PC client which is compiled and designed based on a Python language through an Ali cloud server, and meanwhile protection action parameters (action time, action value, action name and the like) transmitted by the protection device are received. The top of the interface needs to be provided with a static IP address configuration for the Ali cloud, a data receiving and displaying window is arranged below the Ali cloud, and data uploaded to the cloud end by the controller are displayed on the window; and plug-ins for sending commands and a data sending display window are also required to be installed, and command characters sent to the microprocessor by the client are mainly displayed.
WiFi remote control is achieved, and Ariicloud is selected as a data transfer platform. The Aliyun Internet of things platform provides safe and reliable connection communication capacity for equipment, is downwards connected with mass equipment, and supports equipment data acquisition and cloud-up; and a cloud API is provided upwards, and the instruction data is issued to the equipment end through API calling to realize remote control. The Aliyun provides the SDK of the equipment end with multiple protocols such as MQTT, CoAP, HTTP/S and the like, so that the real-time requirement of long connection is met, and the low-power-consumption requirement of short connection is also met. Because the microprocessor has small data transmission amount and the WiFi module has limited transmission capacity, the MQTT protocol is selected to transmit data.
MQTT (Message Queuing Telemetry Transport) built on the TCP/IP protocol, published by IBM in 1999. The MQTT has the greatest advantage that a real-time reliable message service can be provided for connecting remote devices with few codes and limited bandwidth. As an instant messaging protocol with low cost and low bandwidth occupation, the method has wide application in the aspects of Internet of things, small-sized equipment, mobile application and the like. There are three roles in the MQTT protocol: the system comprises a proxy server, a publisher client and a subscriber client, wherein the publisher and the subscriber do not interfere with each other, namely the publisher and the subscriber do not know the existence of each other and only know the proxy server, and the proxy server is responsible for storing and processing messages from the publisher and sending the messages to the correct subscriber.
MQTT enables delivery of messages from a publisher client to a recipient client by way of a "topic". A "topic" is a tag attached to an application message, and the publisher client sends the "topic" and "message" to the proxy server, which forwards the message to each subscriber client that subscribes to the "topic", as shown in FIG. 14.
Due to the fact that data uploaded to the cloud end need to be checked frequently for design and debugging of the WiFi remote control, although subscribed/published data can be observed through a webpage, a computer bears large workload of serial port communication, program compiling and the like, functions of the webpage are large, and most of the data are not visual enough, and therefore the android end is developed independently to receive and control the data. The android end interface is shown in fig. 15.
The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention.
Claims (10)
1. A motor fault detection and protection device is characterized by comprising a voltage and current collector and a motor work monitoring device;
the voltage and current collector comprises a microcontroller, a signal collecting and converting module, a digital-to-analog conversion module, a display module, a relay protection circuit module, a fault indication module, a key module and a communication module;
the signal acquisition and conversion module acquires current and voltage signals of the three-phase motor, converts the current and voltage signals into small voltage signals and sends the small voltage signals to the digital-to-analog conversion module for digital-to-analog conversion;
the digital signal converted and output by the digital-to-analog conversion module enters a microcontroller for data processing analysis and fault judgment, and when the fault of the motor is diagnosed and the protection time is up, the microcontroller controls a relay protection circuit module and a fault indication module to carry out protection and alarm;
the display module displays the working parameters and the state of the motor in real time;
the key module is used for setting rated parameters and fault protection action time of motors of different models;
the motor work monitoring equipment is used for monitoring rated parameters of the motor and current, voltage, power and state under the current work in real time; setting rated parameters and fault protection action time of the protected motor;
the motor work monitoring equipment is in data transmission with the voltage and current collector through the communication module.
2. The motor fault detection and protection device of claim 1, wherein the microprocessor is STM32F103C8T6, and the digital-to-analog conversion module employs MAX 187.
3. The motor fault detection and protection device of claim 1, wherein the communication module is a wireless communication module or a GSM mobile phone card; the wireless communication module selects ESP 8266.
4. The motor fault detection and protection device of claim 1, wherein the relay protection circuit module controls the switching of a relay controlled by an optoelectronic coupling device to achieve the control of a motor power supply;
when the electric energy is too large or the power is too large, the microcontroller outputs a control signal to trip the motor and simultaneously sends out an alarm signal to avoid the motor from generating larger damage.
5. The motor fault detection and protection device of claim 1, wherein the voltage and current collector adopts I2The EEPROM of the communication C is used for storing the time, current and voltage parameters of the motor in failure, parameter setting can be realized, and the set parameters after power failure are stored in the external RAM without resetting.
6. The motor fault detection and protection device according to claim 1, wherein the display module selects an LCD1602 liquid crystal screen to display rated parameters, working voltage and working current of the motor; and when the motor breaks down, fault information and protection action time are displayed.
7. The motor fault detection and protection device according to claim 1, wherein the fault indication module is an LED externally connected to the display module, and is an indicator lamp for detecting voltage, current and communication status with an upper computer.
8. The motor fault detection and protection device according to claim 1, wherein the communication module connects the motor operation monitoring equipment and the voltage and current collector via an Ali cloud server to form a network system for real-time monitoring and data transmission.
9. The motor fault detection and protection device of claim 1, wherein the microcontroller performs data processing analysis and fault determination, comprising:
fourier effective value calculation: filtering discrete and quantized sampling data by adopting an FFT butterfly algorithm and calculating an effective value of the working electric quantity of the motor;
phase detection: calculating the phase difference between each two phases of the three-phase current of the motor according to the discrete and quantized sampling data;
zero/negative sequence current component calculation: calculating zero and negative sequence components of the current according to a symmetrical component analysis method;
fault judgment and protection: analyzing the effective value, zero sequence electric quantity, negative sequence electric quantity and phase difference value of every two phases of the three-phase current, judging whether the motor has a fault, if so, distinguishing the attribution type of the fault, pulling up the starting flag bit of the corresponding fault protection program, and determining the specific fault type to match the corresponding protection measures according to the voltage and current parameters.
10. The motor fault detection and protection device of claim 9, wherein the protection measures are divided into:
overcurrent protection, namely analyzing and protecting data aiming at the symmetric fault;
negative sequence current protection, which is used for analyzing and protecting data aiming at non-ground faults in the asymmetric faults;
and zero sequence current protection, namely data analysis and protection are carried out on the ground fault in the asymmetric fault.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113945781A (en) * | 2021-09-06 | 2022-01-18 | 上海宝康电子控制工程有限公司 | Frequency converter detection system and method |
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