General converter electrical engineer to teach you the overcurrent

General converter electrical engineer to teach you the overcurrent protection and treatment methods Overcurrent protection function of the frequency converter is a very important role in the frequency converter,the following introduce you to the cause of the over current and processing method Frequency converter in the overcurrent protection object refers to with paroxysmal qualitative,peak current,exceeds the permissible value of frequency converter.As a result of the inverter device overload ability is poor,so frequency converter overcurrent protection is a vital link,so far has been very perfect.(1) the cause of the over current A.over current work The current system appeared in the process of work.The reason for this is roughly from the following aspects: A) motor encounter impact load or drive mechanism to the sudden increase of motor current phenomenon of "stuck".B) inverter output short-circuit,such as the connecting line between the output to the motor motor internal short circuit or short circuit,etc.C) inverter itself is not normal work,such as two of the same bridge arm in inverter bridge inverter device in the process of alternating work abnormal.For example due to environment temperature is too high,or aging,the inverter device itself to change the parameters of the inverter device,cause in the process of alternating,a device has been conducting,and another device but also in the future and shut off,causing the same bridge arm of the upper and lower two parts of "straight",the dc voltage between the positive and negative in the short circuit state.

B.over current acc When the load of the large inertia,and set up time and too short,means in the process of advance,the working efficiency of the converter rise too fast,the synchronous speed of the motor because of the large inertia load and couldn't keep up with,and the result is acc current is too big.induction motor price C.over current slow down When the load of the large inertia,and slow down the time set too short,can also cause overcurrent.Because of the slow down,the time is too short,synchronous speed drops rapidly,due to the load and the motor rotor inertia is big,still maintain a high speed,then the same can be the speed of the rotor winding cutting lines of magnetic force is too big and over current generation.(2).Treatment methods A -.When starting A liter of tripping speed,this is very serious phenomenon over current,major inspection (1).Working machinery have stuck (2).Load side if there is any short circuit,check over the ground by megohmmeter for short motor fan circuit (3).The inverter power module if there is any damage (4).The starting torque of the motor is too small,the drag system turns up B.starting without tripping immediately,and tripping in the operation process,the main check: (1).Set up time is too short,longer acceleration time (2).Deceleration time setting is too short,longer deceleration time (3).Torque compensation (u/f ratio) set too big,cause the low frequency time load current is too large (4).Improper electronic thermal relay setting,current action set is too small,misoperation caused by frequency converter

Machine tool equipment electrical troubleshooting - analysis of the failure

Prior to treatment failure,the structure of each part of the electrical equipment action principle,adjusting method and the connection between the parts of electrical equipment,should be a comprehensive understanding,know fairly well.Machine fault,performance can be divided into electrical motor two categories: one is equipment asynchronous motor cannot be specified action,or can not meet the prescribed performance index;Equipment appeared not is the second action,or should not have appeared.For the former,should from the principle analysis on motor run capacitor equipment to set and achieve performance indicators shall meet the conditions,check whether all meet these conditions,find does not meet the conditions and reason.

For the latter,should analysis the fault movement to meet the conditions,and check the electricalmotor1.blogspot.com time those who should not have the conditions,to find out the cause of the false action.All in all,starting from equipment action principle analysis,first find the fault of large range,and then check step by step,from coarse to fine,until we finally found the fault point,and ruled out.For some failure phenomena,not simply for processing,parts should be according to the occurrence,the reasons of the analysis,through the test step by step,to determine the problem,after troubleshooting again electrify test.Don't be reckless,extend the fault,or cause personal and equipment accident.

Common faults and elimination method of induction motor?

(1) motor can't start motor starting,ringing or low speed,this is the most common fault.Its reason is: power disconnection or blown fuse,switch starting equipment or a poor contact or broken line in the stator coil;Or because of lag in the brush brush card,no contact with the slip ring;Stator voltage is too low or excessive load on the reason leads to the failure.Processing methods available voltmeter to check voltage of the motor,such as a phase power lines to check the power supply of power,insurance,switch and starting equipment contact,repair or update processing respectively.If starting rheostat is damaged,can be used to check the lamp or shaking table test,find out the fault repair;If it is found that the load is too big,should reduce or change the capacity of the larger motor. (2) motor overheating causes overload or stator terminal voltage is too high,too low,poor ventilation,may also electric motor have a bolt stator coil,etc.Measures should be taken,such as reducing load,to adjust the mechanical and electrical pressure rating,remove the body ventilation slot dirties dustiness,bolt repair.

 (3) the spark to appear on the slide Reason is lack of the pressure on the slip ring or carbon brush and slip ring dirt,etc.,can be used sand paper to grind is good,with the cleaning brush frame,make the carbon brush block, perkins diesel generator adjust the spring pressure;Also can use clean cloth dipped in a small amount of gasoline,cleaning brush.If spark for slip ring is not round,can take fine car slip ring polishing. (4) motor violent vibration Reason to install more bad,single phase asynchronous motor basic not firm,foot screw is not tight;The individual may also be due to rotor copper bar tensile fracture or short circuit ring.Find out that the former should be correct,which can replace the new copper,the fracture of the available copper weld repair.Sometimes because the rotational part touching the fixed place.Should check the shaft wear and clearance of the stator and rotor,take the fine car rotor or replacement of wearing parts. (5) motor no-load current balance,but value is big 1.The cause of the problem (1) to repair,the stator winding turns to reduce too much;(2) power supply voltage is too high;(3) Y after motor misconnection ;(4) in the motor assembly,rotor installed backwards,making the stator core unaligned,effective length cut short;(5) the air gap is too large or uneven;6 overhaul when the demolition of the old winding,using hot tear open method is undeserved,make the iron core loss. 2.The troubleshooting (1) rewind stator winding,restore the correct number of turns;(2) managed to restore rated voltage;(3) to connect to Y;(4) the new rotor assembly (3) to replace or adjust the air gap;(5) maintenance core or recalculate winding,appropriately increase the number of turns.

servo motor is mainly in the national economy and power-hungry

As is known to all,servo motor is mainly in the national economy and power-hungry,and energy saving is the motor industry an eternal theme.Some experts said,China's energy shortage is mostly caused by three phase induction motor energy waste and improper use.At present,the industrial energy consumption accounts for about 70% of the total energy consumption of electrical energy consumption accounted for about 60%~70% of the industrial energy consumption according to the survey,the level of IE1 motor market share of nearly 90% market share,while firms achieve IE2 above 8% high efficiency and energy saving motor that happened to the entire social resources enormous waste.So,to develop efficient motor is one of the important measures to improve energy efficiency,meet the needs magnet prices of the development of our country,is also very necessary. 

Servo motor rotor squirrel-cage often make it,but in order to make the servo motor has a wide speed range,linear mechanical properties.No "rotation" phenomenon and fast response performance,compared with the ordinary motor,should have the characteristics of small rotor resistance and moment of inertia of the two.The rotor current is widely applied structure has two forms: one is high resistivity of conductive materials made of high resistivity of the conducting bar cage rotor,in order to reduce the rotational inertia of the rotor,the rotor doing long and thin;Another kind is made of aluminum alloy hollow cup induction motor price rotor,glass is very thin,only 0.2 0.3 mm in order to reduce the magnetic resistance of magnetic circuit,should be placed in the hollow cup rotor stator fixed.The hollow cup rotor moment of inertia is small,responsive,and stable running,so widely used. According to our country attaches great importance to enhance the efficiency of the motor,it is enough to illustrate points: one is that in countries currently use less efficient motor,secondly,still have a lot of similar support measures for efficient servo motor.In addition,a good efficient motor mainly rely on import,prices high.In addition,most of domestic enterprises for production of high cost and high efficient motor data "forget and stop" this requires countries increase support for domestic motor manufacturing enterprises,the domestic product market competitive power as soon as possible.

In view of the boiler fan design technologies and solutions

Summary of fan.The fan is one of commonly used equipment factories,enterprises,especially the

application of the fan is more extensive.Boiler fan,smoke prevention and dust control,ventilation cooling fan,is inseparable from the www.Jnmwfj.net in power station,mine,chemical industry and

environmental protection engineering,fan is an important and indispensable equipment,correctly grasp the design of the fan,it is important for guaranteeing the normal economic operation of the fan.The boiler fan design scheme selection Suction fan design is usually given conditions there are

cotton,volume flow,total pressure,working medium and the density of medium temperature (or work),and sometimes the structure requirements and special requirements,etc.For boiler fan design requirements are:to meet the required flow rate and pressure point should be near the highest efficiency point;The highest efficiency value as far as possible a few bigger,flat efficiency curve.Pressure curve of stability interval width;Fan has simple structure,good manufacturability;Easy to select materials and accessories;Have enough strength,stiffness,induction motor sales work safety can be *;Stable running,low

noise;Good regulation performance,strong adaptability to work;Sizes as small as possible,light

weight;Operation and maintenance convenience,easy disassembling transportation.

However,all at the same time satisfy the above requirements,the general is impossible.In the aerodynamic performance and structure (strength,process) often also have contradiction between,usually resolved to seize the main contradiction.This would require the designer to choose reasonable design scheme,in order to solve the main contradiction.Such as:To different requirements,with the purpose of the fan is different also,such as public buildings used by the fan ventilation is generally used to make use of,generally the most important requirement is low noise,wing has the characteristics of the boiler fan;Requires the boiler fan in the heavy traffic are usually double suction type;For some high pressure boiler fan,low specific speed,the leakage loss ratio is generally larger.When the boiler fan design several important scheme:(1) leaf blade type of rational choice:common fan under a certain speed,backward t smaller pressure coefficient of the impeller,the impeller diameter is larger,and its efficiency is higher;The former,by contrast to 12 volt motorthe impeller.(2) the selection of fan drive,such as driving mode for A,D,F,the fan

rotation speed is the same as the motor speed.And B,C,E three are variable,to choose the design

flexible fan speed.General,widely used for small fan and motor to drive straight league A,,for large

fan,belt drive is unwell,sometimes by transmission way D,the F.For high temperature,dusty

conditions,consider the protection of motor,bearing transmission way and the cooling problem.(3) the

overall dimensions of choice:the snail's shell overall dimensions should be as small as

possible.Fan,the ratio of revolution can be used to shorten the volute,standard is generally selected to lower than revolution fan volute.Sometimes in order to reduce volute size,can choose speed is greater than the fan speed for the inlet volute outlet USES the outlet diffuser at this time in order

to improve its static pressure value.

(4) leaf blade outlet Angle selected:blade outlet Angle is designed first to select one of the main geometric parameters.To facilitate the application,we put the blade classified as:strong curved blade (pump),after bending arc blade,straight blade and curved wing shape after bending after blade;Radial outlet blade,radial straight blade;Before the top curved blade,curved blade (wing).Table 1 lists the boiler fan in the blade type of blade outlet Angle range of roughly.(5) leaf number choice:in the boiler fan,increase of the impeller blade number can improve impeller pressure theory,because it can reduce the influence of relative vortex (i.e.,increase the K value).However,the increase of blade number,will increase the friction loss of impeller passage,this loss will reduce the actual pressure of fan and increase energy consumption.Therefore,for each kind of impeller,there is a best leaf number.Specific to determine how many leaf number,sometimes need to according to the designer's experience.According to low rpm motors the current application situation in China,recommend the choice scope of leaf number in table 2.(6) total pressure coefficient t selected:when designing boiler fan,the actual stress is given in advance.Then need to select t total pressure coefficient,total pressure coefficient is roughly options may refer to table 3.(7) the determination of the main geometry size centrifugal impeller import and export:impeller main size is shown in figure 1.The impeller is the only element of fan is passed to the gas energy,therefore,its design has great influence for fan;Can correctly determine the impeller of the main structure,performance parameters of fan plays a key role.It contains the key technologies of the boiler fan design,the design of the blade.

And the design of blade is the most key link is how to determine the blade outlet Angle beta 2 a.The design of the key technologies of analysis When designing boiler fan,the key is to master good determination of impeller blade outlet Angle beta 2 a.According to different blade outlet Angle beta 2 a,the blade can be divided into three types namely the curved blade (beta 2 a < 90 ℃),radial outlet blade gasoline generator spare parts (beta 2 a = 90 ℃ ) and former curved blade (beta 2 a > 90 ℃).Three types of impeller blades,are applied in the design of fan.Before the characteristics of the curved blade impeller are small size weight,cheap,and then curved blade impeller can improve the efficiency,save energy,so in the modern production of the fan,especially the great power of large fan most after using curved blade.Before modern curved blade fan efficiency,than the old product has significantly improved,therefore,on the occasion of small flow high pressure or low pressure big traffic situations are still widely used.Radial outlet blade is not commonly used in our country,in some wear and corrosion resistance of the fan,the commonly used radial export straight blade.Boiler fan impeller design must also take into account the specific speed and blade type has certain relationships (table 4),so the blade outlet Angle is determined at the same time,must consider three kinds of blade type influence on stress,radial size and efficiency,after comprehensive table 1 and table 4.Correctly identified the boiler fan impeller blade outlet Angle beta 2 a will determine the other main geometry size for impeller has laid a solid foundation,thus the performance of the boiler fan plays a key role.

Three-phase motor open phase protection and current changes

Its working principle: Combination switch Q closed first, prepare for motor starting. The main circuit and control circuit and electricity, connect to A, C and two ac contactor coil KM2 electricity, iron core is sucked, concatenated in ac contactor KM1 normally open contacts closed KM2. When press the starting button SB2, ac contactor KM1 electric suction, main circuit of the three main contact closure, auxiliary contact since locking, starting motor M. When there is lack of phase motor, if the lack of A phase or C phase, ac contactor coil KM2, losing electricity concatenated in ac contactor coil KM1 contact KM2 disconnect, make the ac contactor coil KM1 lost electricity, so the lock off contact, the contact is disconnected, the motor can't start losing electricity (right now) or stop; If lack of phase B, ac contactor coil KM1 losing electricity, the lock off contact, main contact disconnect, motor power, can't start (right now) or stop the operation. Thus ensure the motor in diesel generating set the circuit of phase is not 8500w gasoline generator destroyed.