The choice of servo motor electrical engineer

 The choice of servo motor, the distinction between general electrical engineer in accordance with the generally divided into stepper motor, a dc servo motor, brushless dc servo motor, ac servo motor, with the increasingly progress of science and technology, many special servo motor arises at the historic moment, such as piezoelectric motor, linear motor, and the voice coil motor, here we mainly talk about general servo motor selection. Choose what kind of servo motor, to a large extent depends on the physical properties of the load, the load of job characteristics, system requirements and the working environment. Once the system requirement, no matter choose what kind of rotor cutting machine form of servo motor, the first thing to consider is right choose how much of a motor, main consideration physical characteristic of load, including the load torque, moment of inertia, etc. In the servo motor, usually measured in torque or force motor size, so choosing motor first to calculate the equivalent to the size of the shaft end load torque or force. After calculate the torque demand to set aside part of allowance, generally choose motor for times the load torque, torque to the ac synchronous motor reliable running of motor. 

In addition also needs computing reduced to the size of the shaft end load inertia, generally choose the load inertia: motor rotor inertia, to ensure the rapidity of the servo system response. If appear between the motor and load inertia, torque does not match the situation, so only at the expense of speed, increase speed reducer between the motor and load, then you need balance. After selected by how much torque motor, needs to do is to understand the working characteristic of load and working environment. Work load features include such as load is high or low speed running, the acceleration needs to how much, if demand is frequent start-stop, how frequency requirements, system running precision and so on. Then choose servo motor also has no specific rules to follow, the key is your choice of motor must adapt to work to beg you load movement. Such as the system accuracy is not high, the movement speed around hundreds of the following (not more than 500 RPM) but not too low (greater than 1), does not need to frequent start-stop, stepper motor is a kind of good choice. This is due to the stepper motor open-loop control, low control precision, acmotortrading.blogspot.com high speed, motor torque will drop quickly, will take the fixed load, low speed will be rotating discontinuous crawl phenomenon, and the response of the stepper motor is not fast, not suitable for frequent startup applications. When the speed a few turn to more than 3000 turn, relative to demand higher control precision, can choose straight flow or ac servo motor.

The difference between the speed reducer and frequency converter speed control

Electrical engineers Through the difference between the speed reducer and frequency converter speed control of mechanical devices often need to adjust the speed of three-phase asynchronous motor,often use reducer adjustment change frequency reduction ratio or transducer to adjust the speed of the motor. But by what is the difference between the speed reducer and frequency converter speed control? Together (see electrical engineer) to take us to get to know it.Reducer speed:Reducer is through mechanical transmission device to reduce the motor (motor) speed,such as common gear deceleration,turbine worm reducer,etc.Through the reducer to adjust the speed of the motor general need to make sure the following information:1,the types and specifications of the motor,speed,power (or torque),starting characteristics,short-term overload capacity,the moment of inertia,etc.2,the types of mechanical work,specifications,purpose,rotational speed and power (or torque). Working system: constant load or changing load,variable load load diagram; Rev.,braking and short-time overload torque,start frequency; Shock and vibration levels; Direction of rotation,motor and reducer coupling way,whether the shaft extension with radial force and axial force.3,installation type (reducer and motor,the relative position of working machine,vertical and horizontal).

4,transmission ratio and the margin of error.5,environmental temperature,air velocity,dust concentration and environmental conditions such as ph value; (if there is a circulating lubrication and cooling conditions,lubrication station) and the limitation on the vibration and noise.6,to the degree of service life,Motor vehicle safety and reliability requirements.7,the requirement for the size and weight.8,the demands induction motor price of operation and control.9,the source of material,blank,standard parts and inventory.10,on volume,cost and price requirements.11 and delivery term.Frequency converter speed control:Inverter is by changing the frequency of alternating current motor (motor) in order to achieve the purpose of speed regulation. Reduce the motor speed by the frequency converter,you can achieve the goal of energy saving. But generally within 0-50 hz frequency conversion motor to realize the constant torque speed control,within the scope of 50-100 hz to realize constant power speed regulation,and stepless speed regulation,wide speed range.To sum up,through the difference between the speed reducer and frequency converter speed control is mainly: reducer speed a wider range of speed (slow),but generally not stepless speed regulation,speed regulating motor after a lot of physical and electrical parameters can be continued,in addition to the speed loss; And use frequency converter speed control can realize stepless speed regulation,but limited range of speed (only within 3 -- 100 hz speed),speed when affected by a lot of electric parameters,and can't guarantee the original motor of the number of parameters,and fever more serious.

The motor itself the cause of overheating

A circuit,motor winding,when one phase winding break in the motor winding,or in the parallel branch has a branch circuit,will lead to unbalanced three phase current,overheat the motor.B,motor winding short circuit,when the motor winding short-circuit faults on the short circuit current is much bigger than the normal working current,make winding copper loss increases,cause the winding overheating,even destroyed.C,motor connection error,when misconnect into star delta connection motor,motor full load permanent magnet motors for sale operation,still more than rated current flows through the stator winding current,and www.dongfeng-motor.com even cause the motor to stop,if the shut down time is a bit long,not to cut off the power supply,winding is not only a serious overheating,will also be rotor and stator destroyed.

Misconnect when star connection of motor into a triangle,or several coil string into a branch set of motor fault into two branch in parallel,will overheat the winding and iron core,serious when will burn winding.E,motor ac electric motor parts connection error,when a coil,the coil group or a phase windings to reverse,will lead to serious unbalance of three phase current and make the winding overheating.F,the mechanical failure of the motor,when the motor shaft bending,there was something wrong with bad assembly,bearings,etc.,all can make the motor current increases,the copper loss and mechanical friction loss increase,make the motor over heat.

Currently there are 5 kinds of electric vehicles

Brush series brushless dc motor,permanent magnet dc motor,ac motor (induction motor),permanent magnet synchronous motor and BLDC motor FM.Brushless dc series motor are: the advantage is that big start torque,overload capacity is strong,the disadvantage is that need to change the carbon brush,high speed has the ring of fire,not suitable for high speed running,low efficiency,large volume,protection and energy feedback is poor,mainly used in electric tricycle.Brush with permanent magnet dc motor: advantage is better than brushless diesel generator dc series motor has high efficiency,energy feedback is good,starting torque and overload ability general,defect is need to change the carbon brush,high speed has the ring of fire,not suitable for high speed operation,efficiency,large volume,moderate protective ability is poor,mainly used in electric tricycle.

Ac motor,the advantage is simple structure,high reliability of motor itself,the disadvantage is that starting torque is small,large starting current,motor depends on increasing the starting current to produce a large torque,but due to the battery characteristics,the battery provides large current,affects the motor torque,the motor efficiency is low,the control of complex,energy feedback performance is poor.Switched reluctance motor: advantage is in low speed with large torque,defect is low speed vibration,noise,low efficiency,poor energy feedback,rarely used.Permanent magnet synchronous motor,the advantage is with high efficiency,energy feedback acmotortrading.blogspot.com is good,the disadvantage is that when the low speed torque cannot ascend,lose the step problem,rarely used.Brushless dc motor: advantages are: (1) motor external characteristic is good,very accord with the load characteristics of electric vehicles especially motor has low speed high torque characteristics of the precious,can provide large starting torque,satisfy the requirement of the vehicle acceleration.(2) the wide speed range,the motor can run tall in the low speed range,due to mechanical commutator and brush motor,the motor can run under low.(3) motor with high efficiency,especially under the light load cars,motor can still keep high efficiency,it is very important for precious battery power.(4) overload capacity is strong,this kind of motor than Y series motor overload capacity can be improved more than 2 times,can meet the needs of the vehicle bumps blocked.(5) regenerative braking effect is single phase generator good,because of the permanent IE2/IE3 electric motor magnetic motor rotor has the very high,when the car downhill or brake motor generator can be completely into the state,to recharge the battery,the electric braking effect at the same time,reduce the financial burden on mechanical brake.

6.Motor small volume,light weight,high power,can effectively reduce weight,save a space.7 no mechanical commutator motor,USES the totally enclosed structure,prevent dust from entering the motor internal,high reliability.Simple than asynchronous motor was motor control system.Faults is more complicated than the ac motor motor itself,brushless dc motor controller than there are complex.

Questions about the servo zero switch

The change of the method has a lot of kinds,according to the requirements of precision and actual

requirements to select.Could finish (some brand servo motor servo motor itself has a full back to the

origin function),also can through the PC to complete servo,But back to the origin of the principle of

generator rotor and stator common basically has the following several kinds.One,to find the origin of the servo motor,when touching the origin switch,slowing down to stop immediately,to point to the origin.Second,back to the origin directly for encoder The Z believe,when have Z believe that number,slowing down to stop immediately.This method only commonly used in the back to the original axis of rotation,and back to the original speed is not high,the precision is not high also.The installation of the synchronous belt has a great influence on the servo positioning also? This situation,to know whether the servo tuning very soft? Common servo is controlled by pulse,so,the proportion of the position loop gain,speed loop proportional gain,integral time constant,respectively is how much? Proportion of

position loop gain: 21 percentage gain in rad/s speed loop: 105 rad/s speed loop integral time

constant: 84 ms three control modes of the servo There are three kinds of electricalmotor1.blogspot.com general servo control mode: speed control mode,the torque control mode,the position control mode.Want to know is that these three kinds of control mode according to specific what to choose? Speed control and torque control are using analog control.Pulse to control the position control is through the hair.Specific controlled by what way according to the requirements of customers,meet what kind of movement function to choose.If you didn't ask for motor speed,position,as long as a constant torque output,of course is to use the torque mode.If the position and velocity accuracy to a certain extent,and the real-time torque is not very care about,With torque model is not very convenient,with the speed or position mode is better.If the host controller has better closed-loop control functions,with a speed control effect will be better.If the request is not high,or,Almost no real time request,in position control mode has no high demands on upper controller.In the context of the response speed of the servo driver,computation of minimum torque mode,drive the fastest response to control signals;Location model computation,pumps drive the slowest response to control signals.The dynamic performance of sports have higher requirements,the need to adjust motor in real time.So if the controller itself operation speed is slow (such as PLC,or the low end of the motion controller),with the position control method.If the controller operation speed is faster,you can use speed,the position loop from the driver moved to the controller,reduce the workload of the drive,Efficiency (for example,in the most high-end motion controller);If there is a better host controller,can also use the torque mode control,the speed loop also remove in the drive,it generally only high-end dedicated controller to do that,And when does not need to use the servo motor.