Ac servo motor drive is the latest development of a new type of servo system, but also the current machine feeding drive system is a new trend.The system overcomes the shortcomings of the dc drive system, such as frequent maintenance of the motor brush and commutator, large motor size and limited operating environment.It can produce ideal torque in a wide range of speed regulation. It is simple in structure and reliable in operation.
The working principle of ac servo motor is similar to that of two-phase asynchronous motor.However, since it is used as an executive element in the CNC machine tool to convert the ac electrical signal into the angular displacement or angular velocity on the axis, the speed of the rotor is required to reflect the phase of the control signal, and it does not rotate without the control signal.Especially when it is already rotating, if the control signal disappears, it will stop rotating immediately.Ordinary induction motor rotation, if the control signal disappeared, it often can not immediately stop to continue to rotate for a while.
Ac servo motor is also composed of stator and rotor.There are excitation windings and control windings on the stator. The two windings have a space difference of 90° electrical Angle.If a symmetrical voltage with equal amplitude and 90° electrical Angle is applied to the two-phase winding, a circular rotating magnetic field will be generated in the air gap of the motor.If the amplitude of two voltages is not equal or the phase is not 90° electrical Angle, the generated magnetic field will be an elliptic rotating magnetic field.Different signals applied to the control winding produce different magnetic field ellipticity.For example, if the load torque is fixed and the control signal is changed, the ellipticity of the magnetic field can be changed to control the speed of the servo motor.There are three control modes of ac servo motor: amplitude control, phase control and amplitude/phase mixed control.
A digital AC servo system based on space vector algorithm,including the system hardware circuit and system software is designed.Experimental results show that this system meets high-speed,high precision and high reliability required for servo control system.
Articulated robots are generally driven by electric motors where proper controlling signal with proper time synchronism are needed to have control over the movement of the robot. Electric motors employed for the motion control must be operated sequentially and with certain time duration. This paper discusses the motion control of an articulated robot which can be used for precise positioning having applications in various industries. Necessary conditions for the precise positioning of an articulated robotic arm are determined, and ways to control the hand based on these conditions are proposed. A controller circuit is designed which is based on ATmega32L microcontroller for controlling the motion of the motors. It ensures greater accuracy, better speed, flexibility, reduced circuit size and more economical operation than any other control circuit. The whole system is operated by three DC motors which are controlled by H bridge circuits. The controller circuit has been designed and implemented to control the three degrees of freedom of the articulated robot arm.
Electric motors are more likely to burn down than in the past: due to the continuous development of insulation technology,
Motor physical drawing
In the motor design requirements to increase output, but also to reduce the volume, so that the new motor heat capacity is smaller and smaller, more and more weak load capacity;Moreover, with the improvement of production automation, the motor is required to operate in various ways, such as frequent starting, braking, positive and negative rotation and variable load, and higher requirements are put forward for the motor protection device.In addition, the motor is more widely used, often work in the environment is extremely harsh occasions, such as wet, high temperature, dust, corrosion and other occasions.All these, resulting in the motor is more prone to damage, especially overload, short circuit, missing phase, sweep chamber and other faults occur the highest frequency.
2. The protection effect of traditional protection device is not ideal: the traditional motor protection device is mainly based on thermal relay, but the thermal relay has low sensitivity, large error, poor stability and unreliable protection.As a matter of fact, although many equipment is installed with thermal relays, motor damage affecting normal production is still common.
3, the development of motor protection, motor protector has been from the past for electronic and mechanical development of intelligent, can directly show the motor parameters such as current, voltage, temperature, high sensitivity, high reliability, versatility, convenient debugging, after the fault types of protection operation be clear at a glance, both to reduce the damage of the motor, and has greatly helped the fault judgment, to resume production troubleshooting and shorten the time of manufacturing.In addition, motor eccentricity detection technology based on motor air gap magnetic field makes it possible to online monitor motor wear status. By showing the change trend of motor eccentricity degree through curve, bearing wear and faults such as inner circle and outer circle can be detected early, and early detection and treatment can be achieved to avoid the occurrence of bore sweeping accident.
3.Principle of protector selection: reasonable selection of motor protection device, to achieve not only can give full play to the motor overload capacity, but also can avoid damage, so as to improve the reliability of electric drive system and production continuity.Specific function selection should take into consideration the value of the motor itself, the type of load, the use environment, the importance of the main equipment of the motor, whether the motor out of operation has a serious impact on the production system and other factors, and strive to achieve economic and reasonable.
4, ideal motor protector: the ideal motor protector is not the most functional, nor the so-called most advanced, but should meet the actual needs of the site, to achieve the unity of economy and reliability, with a higher performance than price.According to the actual situation of the site to choose reasonable types of protection, function, while considering the protection installation, adjustment, use simple and convenient, more important is to choose high-quality protection.
Selection of protector
The function of the motor protector is to give the motor a comprehensive protection, in the motor overload, missing phase, blocked rotation, short circuit, overvoltage, undervoltage, leakage, three-phase imbalance, overheating, bearing wear, rotor eccentricity, alarm or protection device.
Basic principles of selection:
Motor protection products on the market without unified standards, specifications multifarious models.In order to meet the different needs of users, manufacturers derive a lot of series of products, a wide range of products, to the majority of users to bring a lot of inconvenience to the selection;When selecting the type, the user should fully consider the actual needs of motor protection, reasonably select the protection function and protection mode, so as to achieve good protection effect, improve the reliability of equipment operation, reduce unplanned shutdown and reduce accident losses.
Professional motor maintenance maintenance center motor maintenance process: cleaning fixed rotor - replacement of carbon brush or other parts - vacuum F - level pressure immersion - drying - balancing.
1. The operating environment should be kept dry, the surface of the motor should be kept clean, and the air inlet should not be obstructed by dust, fiber, etc.
2. When the thermal protection of the motor continues to operate, it is necessary to find out whether the fault comes from the motor or the overload or the setting value of the protection device is too low. After eliminating the fault, the motor can be put into operation.
3. Ensure good lubrication of the motor during operation.General motor operation of about 5000 hours, that is, should be supplemented or replace grease, running bearing overheating or lubrication deterioration, hydraulic timely change grease.When changing the grease, remove the old lubricating oil and wash the bearing and the oil groove of the bearing cover with gasoline. Then fill 1/2 (to 2 poles) and 2/3 (to 4, 6 and 8 poles) of the cavity between the inner and outer rings of the bearing with zl-3 lithium grease.
Based on the selection method:
1. Conditions related to model selection
1) motor parameters: motor specifications, functional characteristics, protection type, rated voltage, rated current, rated power, power supply frequency, insulation grade, etc.These contents basically can provide the reference basis for the user to choose the protector correctly.
2) environmental conditions: mainly refer to normal temperature, high temperature, high cold, corrosion degree, vibration degree, sandstorm, altitude, electromagnetic pollution, etc.
3) motor application: it mainly refers to the characteristics required for driving mechanical equipment, such as fan, water pump, air compressor, lathe, oil field pumping unit and other mechanical characteristics under different loads.
4) control mode: the control mode includes manual, automatic, local control, remote control, stand-alone operation, centralized production line control, etc.Start mode has direct, buck, star Angle, frequency sensitive rheostat, inverter, soft start and so on.
5) other aspects: the user's monitoring and management of on-site production, the severity of abnormal shutdown on production, etc.
There are many factors related to the selection of protector, such as installation location, power supply, distribution system, etc.It is also necessary to consider whether to configure and protect the newly purchased motor, upgrade the motor protection, or improve the protection of the accident motor, etc.It is also necessary to consider the difficulty of changing motor protection mode and its influence on production.The selection and adjustment of protector should be considered comprehensively according to the actual working conditions.[4]
2. Common types of motor protector
1) thermal relay: ordinary small capacity ac motor with good working conditions and no frequent start and other harsh conditions;Due to poor accuracy and reliability, it is not recommended.
2) electronic type: detect three-phase current value, the setting current value adopts potentiometer or code switch, the circuit generally adopts analog type, and adopts inverse time limit or fixed time limit working characteristics.Protection functions include overload, missing phase, blocking, etc. The fault type adopts indicator light display, and the running power adopts digital tube display.
3) intelligent: detection of three-phase current value, the protector USES single-chip microcomputer to realize intelligent comprehensive protection of the motor, which integrates protection, measurement, communication and display.The setting current adopts digital setting, which is operated by the button of the operation panel. Users can modify and set various parameters on site according to the specific situation of the motor.Digital tube is adopted as the display window or large-screen liquid crystal display, which can support a variety of communication protocols, such as ModBUS and ProfiBUS.Intelligent protection device is adopted for high voltage motor protection.
4) thermal protection: embed thermal elements in the motor and protect them according to the temperature of the motor windings, with good protection effect;However, when the motor capacity is large, it should be used together with the current monitoring type to avoid the sharp rise of the temperature when the motor is blocked, and the motor winding is damaged due to the hysteresis of the temperature measuring element.
5) magnetic field temperature detector: embedded in the motor test coil magnetic field and temperature measuring element, according to the change of the rotating magnetic field and temperature inside the motor protection, change of main function including overload, locked-rotor, lack of phase, overheating protection and wear monitoring, perfect protection function, defect is need to install magnetic field in motor internal testing coil and temperature sensor.
3. Selection of protector type
1) for the single motor running independently with low requirements on working conditions, simple operation and control, and little impact on production when the machine is shut down, the ordinary protector can be chosen, because the ordinary protector is simple in structure, easy to install and replace on site, simple in operation, and has the characteristics of high cost performance.
2) for the poor working conditions, high reliability requirements, especially involving the automatic production line of the motor, should be selected in the high-grade, more complete functions of the intelligent protector.
3) for the explosion-proof motor, due to the eccentricity caused by bearing wear, high temperature friction may occur in the explosion-proof gap, and explosion risk may be generated. Wear status monitoring function should be selected.For special equipment such as large-capacity high-pressure submersible pump, due to the difficulty in inspection and maintenance, the wear condition monitoring function should also be selected, and the temperature of the bearing should be monitored at the same time, so as to avoid serious economic losses caused by the cleaning chamber accident.
4) protective devices applied in places with explosion-proof requirements should be selected according to the specific requirements of the application site to avoid safety accidents.
Common fault editing
In domestic appliance equipment, if electric fan, freezer, washing machine, take lampblack machine, cleaner to wait, its working power all USES single-phase ac motor.The structure of the motor is relatively simple, so some common faults can be repaired under amateur conditions.
When the motor is energized, it will not start, the motor speed will be slow and weak, the motor shell will be charged, the temperature rise will be increased when the motor is running, the motor running noise will be big, and the body will be overheated.
Notice of the general administration of quality supervision, inspection and quarantine of the Ministry of Industry and Information Technology on the organization and implementation of the motor energy efficiency improvement plan (2013-2015)
Miit coupling [2013] no. 226 the provinces, autonomous regions and municipalities directly under the central government and cities under separate state planning, sinkiang production and construction corps of the competent department of industry and information technology, quality and technical supervision bureau, the central enterprises, for the implementation of the "twelfth five-year" energy saving [2] programmes and industrial energy saving "twelfth five-year" plan, improve the motor efficiency, the upgrade of the motor, the ministry of industry and information technology, the gaqsiq shall organize the formulation of the "motor efficiency plan (2013-2015), and hereby printed and distributed to you.The implementation requirements of relevant organizations are as follows:
1. Promptly organize and formulate the energy-saving transformation plan of the motor system
Regions to organize industrial enterprises eliminated roadmap motor efficiency plan, carry out comprehensive baseline (see attachment 2), guiding enterprises to develop 2013-2015 motor system energy saving transformation and backward solutions, support enterprises choose efficient motor replacing inefficient, priority to motor and drag the equipment matching.Key enterprises with annual power consumption of 10 million KWH or above (local areas can expand the scope of key enterprises according to the actual situation) should fill in the motor system energy saving transformation plan as required (see annex 3) and report to the provincial competent department of industry and information technology for examination, summary and filing.Please submit the summary table (annex 4) of the motor system energy efficiency improvement plan to the Ministry of Industry and Information Technology by the end of September.The competent departments of industry and information technology at all levels should strengthen supervision and inspection, carry out key inspections on enterprises that are not careful in self-examination or have unclear plans for energy conservation renovation, and guide enterprises to formulate three-year renovation and elimination plans as required.
Ii. Carefully organize motor manufacturers to implement mandatory energy efficiency standards
Each region shall organize the motor production enterprises in the administrative region to conduct self-inspection against the national standard (gb18613-2012) of "limited energy efficiency value and energy efficiency grade of small and medium-sized three-phase asynchronous motors", and guide the enterprises to formulate and accelerate the implementation of the standard plan according to the overall requirements of all motor products reaching the standard by the end of 2013.Motor production enterprises should fill in the self-check table of basic situation of motor production enterprises (see annex 5) and report to the provincial competent department of industry and information, quality and technology supervision.The competent departments of industry, informatization, quality and technology supervision at the provincial level shall submit the summary table (annex 6) of motor production enterprises' compliance plan to the ministry of industry and informatization and the general administration of quality supervision, inspection and quarantine before the end of August.By the end of 2013, the Ministry of Industry and Information Technology and the general administration of quality supervision, inspection and quarantine will organize a special inspection on the implementation of energy efficiency standards and labeling.
3. Prepare the pilot program of efficient motor remanufacturing
Shanghai, anhui, shaanxi, hunan, jiangxi and other provinces and cities shall speed up the formulation of pilot work plans for efficient remanufacturing of electric motors.The pilot plan should focus on the key work of building a standardized waste motor recycling system, cultivating large-scale motor efficient remanufacturing demonstration project, improving remanufacturing technology level, and strengthening remanufacturing product quality control, so as to determine goals and tasks, formulate specific measures, define supporting policies, and strengthen guarantee measures.Please submit the pilot work plan to the Ministry of Industry and Information Technology by the end of September 2013.
Recommend a batch of advanced and applicable motor technology
At all levels of industry and information technology departments should actively recommend efficient motor design, control and system matching in areas such as the use of advanced technology, organizing local motor manufacturing enterprises, the energy conservation service company, provided efficient motor and motor system advanced suitable technology declaration form (see attachment 7), by the provincial department in charge of industry and information technology to the declaration material, after preliminary examination and issue the review opinions on August 20 days before the related materials submitted to the ministry of industry and information technology.The Ministry of Industry and Information Technology will screen and compile a catalogue of advanced technologies for improving motor energy efficiency, and strengthen the organization and accelerate the promotion and application of key generic technologies.
Fifth, strengthen publicity and training
All regions should make full use of the Internet, radio, television and other channels, strengthen publicity and reports, and quickly publicize the national policies and measures on improving motor energy efficiency to key power enterprises, motor manufacturers and related institutions.Provincial competent departments of industry and information technology shall formulate local training plans, organize training for heads of municipal and county competent departments of industry and information technology, energy conservation supervision institutions, key enterprises and technical personnel, and complete business training for key power enterprises that consume 10 million kilowatt-hours of electricity per year or more by the end of 2015.To do this well, the Ministry of Industry and Information Technology will set up a team of experts, compile and publish textbooks, organize training for provincial departments in charge of industry and information technology, energy conservation supervision institutions and some key enterprises, and support and guide local training.
