Predictive control

In this method,through the flux linkage space vector and voltage vector relation can be get:The S is under the effect of voltage vector flux amplitude change of amount,theta V is both space Angle. Sampling period of flux linkage error is set the first k SO,SO [5] according to the formula,can get the first k+1 cycle of flux linkage error is zero vector function for time. To the principle of torque control priority according to the calculated acmotortrading.blogspot.com torque predictive control time and flux linkage vector function of predictive control calculated time can get comprehensive vector function of time. After considering magnetic chain of beat control compared to the pure torque without beat control effect is good,is to eliminate the torque ripple,and won't produce magnetic chain distortion,and will not be too large amount of calculation. In addition to the torque difference frequency control method,also adopted a similar approach in the literature,the voltage vector calculation time is basically the same,not detailed here. Like Habetler no beat method,forecasting method also need more motor parameters,if you can online real-time identification of ac alternators 220v the stator resistance and rotor time constant,will greatly improve the control precision. 

Direct torque control in discrete time Discrete-time direct torque control using the method of discrete time control of asynchronous motors in the literature have more detailed introduction,in the

literature,for the first time this kind of method used in direct torque control,the base is as

follows: the method of the basic circuit of the motor voltage equation and flux equation obtained by

model discretization is as follows:Type a,b,the definition of the counter rotating torque equations

are discretized,and once the equation in which,at the same time also once into the equation to the

flux amplitude square expression,using discrete torque equation and discrete flux amplitude flat way can solve out the next cycle of space voltage vector increment VSx and VSy,plug in the following equation of torque and flux can be obtained without beat control of voltage vector,and on the limit:Discrete-time direct torque control can be achieved by difference equation,the k+1 cycle should reach the torque and flux linkage pass out,so we can both meet the torque and flux of beat control,from the implementation approach is very suitable for gasoline generator spare parts digital control,in addition to control,this method is mainly based on the stator side required motor stator resistance and inductance parameters,better robustness to the motor parameter changes,from the point of the experimental results,the dynamic response of the system performance is better. In this approach,however,need to detect phase voltage of the motor,the increase of the complexity of the hardware of the system,in addition,a fairly large amount of calculation.

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.

The principle of three phase asynchronous motor

Creates a to synchronous speed n1 along the circle space inside the stator and rotor rotate clockwise rotating magnetic field.Due to the rotating magnetic field in the n1 speed rotation,the rotor conductor is still at the beginning of the rotor conductor will cut the stator rotating magnetic field and produce inductive electromotive force (judge the direction of the induced electromotive force with the right-hand rule) due to the rotor conductors sub is short circuit loop at each end,and the effect of induction electromotive force,the rotor conductors will occur basic consistent with the direction of induction electromotive force induced current.

Rotor current carrying conductor in the role of the stator magnetic field by electromagnetic force (force in the direction of the left small electric motors hand rule determine) electromagnetic force on electromagnetic torque,rotor shaft drive Motor vehicle rotor spinning in the direction of the rotating magnetic field.By analyzing the working principle of the motor can be summarized as follows: when the three-phase stator winding of the motor (the difference between a 120-degree Angle) to the balanced three-phase alternating current (ac),will happen in a rotating magnetic field,the rotating magnetic field cutting rotor winding,which occur in the rotor winding induced current (rotor winding is closed-cycle) rotor of current-carrying conductor in the stator rotating magnetic field under the action of electromagnetic force will occur,as to form the electromagnetic torque on the motor shaft,motor rotation,and the motor rotation direction is the same as the rotating magnetic field direction.

Output voltage space vector method

In direct torque control,if we can get any phase of space voltage vector,will help to reduce the

torque ripple under low-speed,reach the steady state performance of vector control at low speeds.In the third quarter no beat control can get any phase of space voltage vector,but calculation is more complex,more difficult.Another for any phase of space voltage vector method is to use PI regulator.A.b.induction motor salesPlunkett direct torque and flux adjustment method is A kind of PI adjustment method,only then had not space voltage vector this concept,can only use the method of SPWM output voltage motor control.In the literature,the proposed method of direct torque control using PI control,and output space voltage vector for the SVM method. Obtained by torque and torque feedback given error input torque PI controller,PI adjustment get q axis acmotortrading.blogspot.com voltage vector and stator flux and stator flux feedback given by the gain of the stator flux linkage error input PI regulator,PI regulation to obtain d shaft voltage vector,then d axis and q axis voltage vector rotation transform the alpha shaft under the static coordinate system and beta,used for the output of the space voltage vector,clearly the space voltage vector in the phase space position is arbitrary.

Structurally similar direct torque control based on PI control on the stator flux vector control,but there is a difference between the two,the stator flux vector control based on synchronous rotating coordinate system,the stator flux orientation in d axis,q axis flux is zero in the d axis direction and the flux and q axis direction of current decouple,and these for direct torque control based on PI control does not need to,among them only need to make the output torque and stator flux feedback can be given by PI regulating method to follow,so from the implementation is relatively simple,robustness is also good at the same time,and compared with the traditional gasoline generator spare parts direct torque control can improve the switching frequency,reduced torque ripple under low-speed,but in this method need to select the right PI parameters,otherwise it will affect the control system dynamic and static performance.In addition to the above this kind of PI control of direct torque control,also in the literature in a.b.Plunkeet direct torque and flux control method on the basis of further research,the use of space voltage vector way output,not detailed here.

good performance cheap high efficient ac induction motor

7.Why stepper motor torque will vary with the increase of rotational speed down? When stepping motor rotation,the motor of each phase winding inductance will form a reverse electromotive force;The higher the frequency,reverse electric The greater the potential.Under the function of it,the motor with frequency (or speed) and the phase current decreases,which leads to torque decline.8.Why can generator rotor and stator operate properly when stepping motor at low speed,but above a certain speed won't be able to start,accompanied by whistler? Step motor has a technical parameters: no-load start frequency,namely step by step Motor under no-load condition can normal boot pulse frequency,if the pulse frequency is higher than the value,the motor does not start properly,may be lost or blocked.In a load Under the condition,Start frequency should be lower.If you want to make the motor to achieve high-speed rotation,the pulse frequency should be to accelerate the process,the start frequency rate is low,and then in a certain high frequency acceleration to want (electricity Machine speed from low speed to high speed).9.How to overcome the two-phase hybrid stepping motor vibration and noise during low speed? 

Stepper motor rotates at low speed vibration and noise is its inherent shortcomings,can adopt the following solutions to commonly Overcome: a.if the stepper motor work on resonant zone,but by changing the reduction ratio and other mechanical transmission to avoid the resonance region;B.using with the function of subdivision drive,this is the most commonly used,The easiest way;C.to step away from the Angle brake rotor of smaller stepper motor,such as three-phase or five phase stepper motor;D.for ac servo motor,can almost completely overcome the vibration and noise,but become This is higher;E.add magnetic damper on the motor shaft,on the market for this product,but the mechanical structure change is bigger.10.The fine fraction of subdivision driver can represent accuracy? Stepping motor subdivision technology is essentially an electronic damping technology (please refer to the relevant literature),its main purpose is to reduce or eliminate the weak Eliminate the low-frequency vibration of the stepping motor,improve the operation precision of the machine is only a supplementary function of subdivision technology.

Such as in the step Angle is 1.8 ° two-phase hybrid stepping motor,if fine Points drives the fine fraction of set to 4,then the motor running resolution for each pulse 0.45 °,the precision of the machine can achieve or close to 0.45 °,still depends on the subdivision driver segmentation Other factors such as current control accuracy.Different manufacturers of subdivision drive accuracy

may vary widely;The more difficult it is to fine grade,the greater the precision control.11.With four

phase hybrid stepping motor drives the series connection and and what is the difference between the

connecting method? Generally consists of two phase four phase hybrid stepping motor driver to

drive,therefore,the connection can be used Series connection or parallel connection to connect two

phase using four phase motor.In series connection in place of motor speed electricalmotor1.blogspot.com is used commonly,the need to drive the output current for the motor phase current of 0.7 Times,thus motor heating small;And connection generally use in motor speed higher occasions (also called high speed connection),needed to drive the output current for the motor phase current of 1.4 times,and electricity Fever is relatively large.

With a brush brushless

Brushless dc motor is composed of stator main body of the motor and drive, is a typical mechatronics product. The stator winding of the motor to make more balanced three-phase y connection, With three phase asynchronous motor is electrical motor 24v very similar. On the rotor of the motor with the magnetization of the permanent magnet has, in order to detect the polarity of the motor rotor, inside the motor is equipped with position sensing Device. Drive consists of power electronic devices and integrated circuit, its function is: accept the motor start, stop, brake signal, to control the start and stop of the motor Check and brake; Accept the position sensor signals and positive &negative, used to control the inverter bridge on and off of each power tube produce continuous torque; Accept the speed instruction and feedback Signal, which is used to control and adjust the speed; To provide protection and display, and so on. Because of brushless dc motor based on self-control type operation, so don't like frequency control of motor speed synchronous motor overload start under plus startup winding on the www.dongfeng-motor.com rotor, also do not When the load mutation generate oscillation and step out. Medium and small capacity of the permanent magnet brushless dc motor (BLDCM), now more than using high magnetic energy product of rare earth ndfeb material (Nd - Fe - B) Material. As a result, the volume of rare earth permanent magnet brushless motor than three-phase asynchronous motor with capacity reduces a frame number. Nearly thirty years in view of the asynchronous motor frequency control of motor speed Research, in the final analysis is looking for a way to control the asynchronous motor torque, rare earth permanent magnet brushless dc motor is bound to its wide speed range, small volume, high efficiency and steady state Speed and small error characteristics appeared in the field of speed advantage. Because of brushless dc motor has the characteristics of a dc motor, is also the electrical motor 12v 1000w device of frequency variation, so also known as straight Flow frequency conversion, the international general term for BLDC) motors running efficiency of the brushless dc motor, torque at low speed, precision of speed is more good than any of the control technology of inverter, so value Attention to the industry. The product has production more than 55 kw, can design to 400 kw, can meet the requirements of industry energy saving and high performance drive. 

1, fully replace the dc motor speed control, comprehensive alternative, comprehensive alternative to asynchronous motor frequency converter + frequency conversion motor + reducer speed; 2, can run for high power at low speed, can save the reducer direct drive big load; 3, have all the advantages of traditional dc motor, and cancelled the carbon brush and slip ring structure; 4, torque characteristic is excellent, medium and low speed torque performance is good, big start torque, small starting current; 5, stepless speed regulation, wide speed range, strong overload capacity; 6, small volume, light weight, large output; 7, soft and soft stop, good braking performance, saves the original mechanical braking or electromagnetic braking device; 8, high efficiency, no excitation loss and carbon brush motor itself loss, eliminate the multiple reduction consumption, comprehensive energy-saving rate can reach 20% ~ 60%, power saving a year only to recover Cost; 9, high reliability, good stability and strong adaptability, simple maintenance and maintenance; 10, turbulence shock resistance, low noise, little vibration, smooth operation, long service life; 11, no radio interference, does not produce sparks, especially suitable for explosive place, explosion-proof type; 12, according to the needs of optional trapezoidal wave motor and is XuanBo magnetic field magnetic field. 21 points for attention (1) before disassembly, should surface dust with compressed air blowing off the motor, and scraped perkins diesel generator set clean surface dirt. 

2 choose motor working place, the disintegration of the clean up the scene environment. (3) familiar with the motor structure characteristics and maintenance technical requirements. (4) ready to collapse the required tools and equipment (including special tools). 5] in order to further understand the defects of the motor running, conditional when can do an inspection test before disassembly. Therefore, the motor with load test, detailed inspection machine Parts, such as temperature, sound, vibration, and test the voltage, current, speed, etc., and then disconnect the load, do a no-load check test, measure and no-load current No-load loss, recorded. [6] to cut off the power supply, electrical wiring to remove, recorded. Once the appropriate voltage test motor insulation resistance by megger are. Maintenance in order to keep up with The Times when measured insulation resistance compared to judge the trend of change motor insulation and insulation State, different temperature should be measured insulation resistance value conversion to the same temperature, the average conversion to 75 ℃. Being tested to absorb than K. When the absorption ratio greater than 1.33, which indicates that the motor insulation or degree of be affected with damp be affected with damp be affected with damp be affected with damp or not serious. In order to compare with previous data, should will likewise Any temperature measured absorption than the conversion to the same temperature.

Electronic commutation motor

ECM motor in forced air furnace and in order to save electricity of the HVAC system is used more and more,because of induction motor sales the HVAC system of fan running for a long time in the daytime.In the cost efficiency of the HVAC system with ECM motor is still questionable,the cost of the repair this motor is www.facebook.com/guohong.trading almost equal to or even more than saving it.Other single-phase capacitor motor general principal deputy for the parallel operation,the main current in our actual use load range of 90 degrees or so, You can get the best performance;And series connection generally appear in one pole winding speed regulating pole change motor,when in actual use NaZhu vice around the load ac alternators 220v range Consistent set of basic Angle,unable to form a circular magnetic field.