power factor compensation

An overview,In ac circuits,the phase difference between voltage and current cosine is called power

factor,with symbol cos said on numerical value,the power factor is the ratio of active power and

apparent power,namely the cosine = P/S.Power load of power grid,such as motor,transformer,fluorescent

lamp and the electric arc furnace and so on,mostly belong to the inductive load,the motor inductive equipment in operation process is not only need to absorb the active power in power system,also absorb reactive power at the same time.So the parallel capacitor reactive power compensation equipment installed in the power grid,will be able to provide compensation reactive power consumed by a perceptual load,reduce the power grid power supply side perceptual load and by line transmission of reactive power.Reduce the reactive power flow in the grid,can reduce the transmission and distribution lines transformer and bus power loss caused by the transmission of reactive power,this measure is called power factor compensation.Owing to the rise in the power factor is the root cause of the reactive power reduce,so often called power factor compensation of reactive power compensation.In a large system,reactive power compensation is also used to adjust the voltage of power grid,improve the stability of power grid.In a small system,through proper reactive power compensation method also can adjust the unbalanced three-phase current.According to the wangs theorem:in phase to phase and jumper inductor or capacitor can be transfer active current.For three-phase current unbalance of system,therefore,as long as appropriate in each phase to phase and phase zero access between different capacity of capacitors,acmotortrading.blogspot.com not only can be in each phase of power factor compensation to 1,and can make the active current of each phase equilibrium state.Second,the method System of compensation for reactive power compensation's main purpose is to improve the power factor.

Because of the power supply bureau of electricity is KVA or MVA to calculate,but the fee is to KW,which is actually doing useful work rate,a reactive power between the difference,in general is the reactive power in KVAR.Most lost work are inductive,that is generally called motor,transformer,fluorescent lamp.almost all of the lost work are inductive,capacitive is very rare.That is because of the existence of the inductive,caused a KVAR value in the system,is a trigonometric function relationship between the three KVA square = KW square+KVAR square Simple speaking,in the above formula,if today's KVAR value is zero,KVA will be equal to KW,the power supply bureau of 1 KVA electricity is equal to the user 1 KW consumption,the most cost-effective,so the power factor is a factor of power supply bureau is very care about.The power factor of the user if there is no ideal,relatively is the resource consumption in power supply bureau,so that is why the power factor is a regulatory restrictions.At present in terms of domestic power factor regulation must be between 0.9~1 inductive,below 0.9 need to accept the punishment.This is why we have to control the power factor in a very sophisticated.Some of the power electronic equipment such as rectifier,inverter,switching power supply,etc.; Saturable equipment such as transformers,motors,generators,etc.; Electric equipment and three phase induction motor price electric light source equipment such as electric arc furnace,fluorescent lamp,etc.,these devices are the main source of harmonic,the runtime will produce large amounts of harmonic.Harmonic on the engine,transformers,motors,capacitor etc all electrical equipment connected to the grid size,main show is harmonic generation additional loss,make the insulation of the equipment overload overheat and harmonic overvoltage accelerated aging,etc.Parallel to the line on the reactive power compensation capacitor to the harmonic amplification effect,causing the system voltage and current distortion is more serious.In addition,the harmonic current superimposed on the fundamental wave current of capacitor,can make the capacitor current of effective value increase,leading to higher temperature,reduce the service life of the capacitor.Harmonic current increase the copper loss of transformer,cause local overheating,vibration and noise increases,additional heating winding and so ac alternators 220v on.Harmonic pollution can increase cable transmission line loss.And harmonic pollution affect communication quality.When the current harmonic component is higher,may cause relay protection of overvoltage protection,overcurrent protection misoperation.Therefore,if the system is of high harmonic content,in addition to the series capacitor side need appropriate tuning (detuned) reactance,and installation of harmonic improve device for load characteristic project discussion.