1,brush current density is too large.In the actual operation,if one or two brush jamming due to
mechanical trouble,lack of spring pressure don't output,in order to maintain the normal load,by other
brush of current will increase,if there are in the increasing flow of the brush the slant of the
brush,because with the slip ring contact area is reduced,surface flow density increases.According to
Q = I * IRT,calorific value and is proportional to the square of the current,the accumulation of heat to send out,the temperature rise sharply,the brush and slip ring interface can produce sparks.Also spark,after the creation of the brush work environment more bad,so a vicious circle,make brush sparks more serious,a few have this severe cases will occur when the three phase induction motor ring of fire.2,uneven brush pressure,or do not conform to the requirements.
Brush factory manufacturers are
related: brush spark does not occur to the lowest pressure,pressure adjustment go through scientific argumentation and practice summary,minimum pressure generally is 200 ~ 300 ㎡ ɡ / c,is 0.02 ~ 0.03 MPa,the pressure between each brush also wants even,its difference is not more than 10.The generator in the long run if a brush friction are too short,or brush in the brush frame www.dongfeng-motor.com delay CARDS,pressure will be uneven.Moreover by machinery,heat soft spring itself and other factors affect the pressure can not meet the brush doesn't happen spark theory of minimum requirements.And we are compaction,tyra carbon brush,sometimes feel,no accumulation of experience,operating error is very great.3,the surface of the brush is not clean.
This is the most let people ignore,normal operation of the generator brush
seal inside the airtight cabinet,there are set on the shaft gear shape among the poles brush axial flow fan,depend on rotor rotating grinding of graphite carbon powder,heat away in time,brush to clean ac geared motor the cooling effect.If the cupboard door closed lax,or forget to close the door,when checking out the dust with the hot air into the brush,brush attached to the column,on the one hand brush heat dissipation.On the other hand brush spark occurs due to brush the column surface impurity,brush column insulation strength between ring fire easily.Besides slip ring on have spiral groove,this is in order to increase the brush the cooling area,improve with brush contact,makes the brush more fully cooling,at the same time are more likely to make carbon powder.If cupboard door closed lax,lack of draught fan outside dust very easily also adhere to the spiral ditch,consequences was palpable.Excitation single phase capacitor start induction motor electrical and mechanical brush consider its bare outside,the lower voltage level in this also suggests the maintenance regularly clean.A few days ago excitation brush sparks was forced to stop incidents happened in our factory,the reason of many sided,often small disaster.We should cause enough attention.
Early study of permanent magnet synchronous motor mainly in fixed frequency power supply of the working characteristic of the permanent magnet synchronous motor research,especially the research of steady-state characteristics and direct starting performance.Permanent magnet synchronous motor starting directly depend on damping windings provides asynchronous torque motor speed up to close to synchronous speed,and the magnetic resistance torque and torque will be synchronous motor pull in sync.V.B.H onsinger and M.A.R ahman et al.A lot of research work has been done in this single phase capacitor start induction motor respect.In the eighty s,foreign to inverter power supply of permanent magnet synchronous motor for further research.Inverter power supply of permanent magnet synchronous motor with direct starting of the structure of the permanent magnet synchronous motor are basically the same,but in most cases without damping windings.Damping winding has the following characteristics: first,damping winding to generate heat,make the permanent magnet temperature rise; Second,increase the moment of inertia,damping winding motor moment of inertia ratio decline; Third,the tooth of the damping winding make pulsating torque increases.In inverter power supply situation,it will affect the original characteristics of permanent magnet synchronous motor,the steady state and transient characteristic of permanent magnet synchronous motor with a constant frequency compared with different features.
A large number of papers published after 1980 study the mathematical model of permanent magnet synchronous motor,the steady state characteristics,dynamic characteristics.A.V.G umaste research such as the voltage type inverter power supply of permanent magnet synchronous motor steady state characteristics and the current type inverter power supply of permanent magnet synchronous motor steady-state characteristics.With the constant improvement of the permanent magnet synchronous motor speed control system performance requirements,the perkins diesel generator need to design high efficiency,high moment of inertia ratio,high energy density of permanent magnet synchronous motor,G.R.S lemon and others diesel generator for speed control system dynamic performance and high efficiency requirements quickly,modern design method of permanent magnet synchronous motor is presented.With the development of microcomputer technology,permanent magnet synchronous motor vector control system of full digital control also has made great development.D.N aunin a permanent magnet synchronous motor is developed,such as right amount control system,using a 16 bit single chip microcomputer 8097 as control computer,realizes the high accuracy,high dynamic response of full digital control.
In the late eighty s,early ninety s B.K.B ose and published a large number of permanent magnet synchronous motor vector control system of full digital control of the paper.Speed controller of permanent magnet synchronous motor vector control system usually adopts proportional integral (PI) control.PI controller has a simple structure,good performance and is not sensitive to controlled object parameters change,etc.In 1991,R.B.S epe adopts self-tuning control in the speed controller for the first time.Early adaptive control is mainly used in dc motor adjustable beam system.National Taiwan university tian-hua liu and so on for the first time the robust control theory is applied to permanent magnet synchronous motor servo drive.Motor in the process of running,the model and the parameter is constantly changing,the change of the parameters and model will cause to reduce the performance of control system.All kinds of robust control technology in modern control theory to make the control system in the model and parameter changes to protect the good control performance.Will,therefore,all kinds of robust control technology used in motor speed regulation,can greatly improve the performance of speed control system.In this regard,the use of more successful control technology mainly include: adaptive control,variable structure control,parameter identification technology,etc.
