Motor maintenance process
Motor protection knowledge
1, motor burned more easily than in the past: due to the continuous development of insulation technology
Both requirements increase output in the motor design requirements, and reduce the volume of the heat capacity of new motor, more and more small, overload ability is more and more weak; due to the production of the exaltation of automation degree,requirements of motor always runs in frequent starting, braking, positive inversion and variable load in a variety of ways, put forward higher requirements for motor protection device. In addition, the application of the surface of the motor more widely,often working in the environment is extremely bad situations, such as humidity, high temperature, dust, corrosive occasions. All of these, resulting in motor are more easily damaged, especially overload, short circuit, phase lack, such as fault occurs at the highest frequency sweep chamber.
Develops the current situation 2, motor protection: motor protector has a mechanicaldevelopment in the past to electronic and intelligent, and can directly display the motor current, voltage, temperature and other parameters, high sensitivity, high reliability, more functions, convenient debugging, fault types of protection action is clear at a glance, can reduce motor damage, and greatly facilitate the fault judgment,is conducive to the production site of the fault treatment and shorten the recoverytime of production. In addition, motor eccentricity detection technology using the motor air gap magnetic field, the motor wear condition online monitoring possible, the curve shows the variation trend of motor eccentric degree can be found early, bearing wearand go inside the circle, the outer circle fault, accomplish early discovery, earlytreatment, avoid sweeping accidents.
3, the traditional protection device protective effect is not ideal: motor protectiondevice in the traditional thermal relay thermal relay, but low sensitivity, large error,poor stability, protection is not reliable. The fact is that, although many of the equipment installed in the thermal relay, but motor damage and affect the normal production of the phenomenon is still widespread.
Motor protection device 4, the ideal: ideal motor protector is not the most functional,nor the most advanced, but should meet actual demand, achieve the unity of economy and reliability, high ratio of performance to price. The reasonable choice ofprotective device types, function according to the actual situation, consideringprotector installation, adjustment, simple and convenient to use, it is more important tochoose high quality protection device.
5 protective device selection principles: reasonable selection of motor protectiondevice, both can give full play to the overload ability, but also from damage, so as to improve the reliability and the continuity of the production of electric drive system. The specific function of choice should be integrated into the motor itself value, load type,use of the environment, the motor main body equipment of important degree, motorout of operation for production system cause serious impact and other factors, and strive to achieve reasonable economic.
Professional electrical maintenance center maintenance: cleaning process of motorrotor - replace the carbon brush or other parts of vacuum pressure impregnation F level - drying - balancing school.
1, when the motor thermal protection continuously happen action, should find faultfrom motor or overload or protection device setting value is too low, eliminate malfunction, can be put into operation.
2, the use of the environment should be kept dry, motor surface should be kept clean,air inlet to dust, fiber and other obstacles.
3, when the end of the life of the bearing, motor running vibration and noise willincrease obviously, check the radial clearance of the bearings to the following values,i.e.replace bearings.
4, should ensure good lubricating motor during operation. General motors runningabout 5000 hours, should complement or replace grease, bearing overheating or lubrication modification found in operation, the hydraulic timely for lubricating grease.Replacing the grease, should remove old lubricating oil, and oil tank of gasolinecleaning bearings and bearing cover, and then the ZL-3 lithium grease filling a cavity between the inner and outer rings of bearing 1/2 (2 pole) and 2/3 (4, 6 and 8 poles).
5, the replacement of winding must take note of the primary winding form, size andnumber of turns, wire, when the loss of the data, should be available to manufacture factory, arbitrarily change the original design the motor winding, often one or severalperformance deterioration, and even can not be used.
6, removing the motor, from the shaft extension end or extension end of rotor can be taken out. If it is not necessary to remove the fan, or from a shaft extension end out rotor is more convenient, from out of the rotor in the stator, stator winding insulation should prevent damage or.
There are many factors associated with protective device selection, such as the installation position, power, power distribution system and so on; consider is on the purchase of new motor protection configuration, or the motor protection upgrades, oron the accident of motor protection improvement; consider changing motor protection mode of production difficulty and the degree of influence; according to the the site conditions of the actual work considering the selection of regulator and protection
Common types of motor protector
1) thermal relay: Ordinary small capacity of AC motor, the working condition is good,does not exist frequent startup bad working circumstance; because of poor accuracy,reliability can not be guaranteed, not recommended.
2) electronic type: detection of three-phase current value, current setting value using a potentiometer or pull code switch circuit using simulation, inverse time or time limitoperating characteristics. Protection features include overload, lack of phase, locked rotor, fault type using light show, power operation using digital tube display.
3) intelligent: detection of three-phase current value, protector of the use of SCM,realize motor intelligent comprehensive protection, protection, measurement,communication, display as a whole. Setting current using digital setting, to operation through the operating panel button, the user can according to the specific situation ofmotor in the field of all kinds of parameters correction setting; the use of digital tubeas display window, or by using a large screen liquid crystal display, can support a variety of communication protocols, such as ModBUS, ProfiBUS and so on, the price is relatively high, for the more important occasions; protection high voltage motor adoptsintelligent protection device.
4) thermal protection type: buried heat element in the motor protection, according to the motor winding temperature, good protection effect; but the motor capacity is large,to be used in conjunction with the current monitoring type, avoid the motor locked rotor temperature rise sharply, due to the lag of temperature measuring elements,resulting in impaired motor winding.
5) the magnetic field temperature test type: embedded magnetic field detection coiland a temperature measuring element in the motor protection, according to the change of internal motor rotating magnetic field and the change of temperature, the main functions include overload, locked rotor, lack of phase, overheat protection andwear monitoring, perfect protection function, the disadvantage is the need to install a magnetic field detecting coil and a temperature sensor in the inner part of the motor.
The choice of the type of protection device
1) for working condition requirements is not high, simple operation, shutdown ofstand-alone operation of motor production impact is not big, can be common typeprotector for the ordinary type protector has the advantages of simple structure,wiring installation on site, convenient replacement, simple operation, high ratio of performance to price and so has the characteristics of.
2) for severe working condition, high requirements for the reliability, especially motorrelates to an automatic production line, should be used in high-grade, relatively complete functions of intelligent protector.
3) for explosion-proof motor, because the bearing wear caused by eccentricity, may lead to explosion proof clearance of friction appears high temperature, explosion hazard, should choose to wear condition monitoring function. For large capacity high-voltage submersible pumps and other special equipment, the inspection and maintenance difficulties, also should choose state monitoring function and wear, while monitoring the temperature of the bearing, to avoid sweeping accidents cause great economic losses.
4) applied to a protector for explosion-proof requirements places, according to the specific requirements of the application site, the selection of explosion-proof type protector accordingly, avoid safety accidents.
The motor is energized after starting, motor speed is slow and weak, motor shellcharged, a running motor temperature rise intensifies, running noise of motor, body overheat.
In household appliances, such as electric fan, refrigerator, washing machine,lampblack machine, the vacuum cleaner, the working power adopts single-phase AC motor. This motor has the advantages of simple structure, so some common faultscan be repaired in the amateur conditions.
