0
VAr is reactive power, caused by either inductive or capacitive loads. The ideal power factor to have is 1, anything less than that is a loss on the network. The effect of VArs on the circuit though depends. If you have a load that is mainly inductive, then adding more inductive reactance will lower the power factor. However, if you introduce capacitive reactance this will increase the power factor, and the opposite is true if its a mainly capacitive circuit. So VArs will either increase or decrease the power factor depending on the load of the circuit. The ideal situation is to balance inductive reactance with capacitive reactance so they in effect cancel each other out and power factor is 1.
Wiki User
∙ 14y ago
Add your answer:
Earn +20 pts
Why the power factor of a transformer is poor at no load?
The inductance of the transformer is much higher than the resistance of the transformer, resulting in very low real power losses (in watts), but some reactive power (vars).
Can a watt meter that has current through its current coil and a potential across its voltage coil indicate zero?
A watt meter that has current through its current coil and voltage across its voltage coil will indicate zero if the power factor between the volts and amps is zero. This condition would be one in which the current will either lead or lag the voltage by 90 degrees and the circuit will have amps, volts, VARS, and VA, but will not have Watts.
What is MVA as a power term?
mega volt amperes 1 MVA = 1000KVA, 1KVA = 1000VA VA is equivalent to Voltage times current; it includes both real (watts) and reactive (vars) power; In techno speak it is the vector sum of real and reactive power. Thus it is a useful term for calculating the size of equipment necessary, since equipment must be sized for total current flow (both real and reactive contribution).
What is the formula used to calculate electrical power in a dc circuit?
Electric power is a measure of energy per unit of time.For example: 1 volt=1 joule (energy)/ 1 coulomb (electric charge)1 ampere=1 coulomb/1 second1 watt=1 joule/1 secondIn a direct current circuit, P (watts)=V (volts) x I (amps)For direct current:P=VxIP=I^2RP=V^2/RWhere R is resistance (ohms).For alternating current:S=P+jQS=VI* (I* means complex conjugate of I)S=sqrt(P^2+Q^2)V=IxZZ=R+jXSo P is the real part of S and Q is the imaginary part of S.S is in unit of volt-amperes, P is in watts and Q is in vars (volt-ampere reactive).X is reactance and is calculated by either jwL or 1/jwC or both depending on what components are in the circuit.w is 2xpixfrequency of the AC circuit. L is inductance and C is capacitance.CommentThere is no such thing as 'electrical power'. Power is simply a rate -it is neither electrical, mechanical, or anything else!
What happens if the synchronous motor exceeds its load capacity?
If load on a generator is greater than the generator can provide, the generator will begin to slow down. If it slows down too much, it will lose synchronism.
Can transformer be operated on lead power factor?
Yes, there is no problem in transmitting capacitive VARs if they occur.
Why the power factor of a transformer is poor at no load?
The inductance of the transformer is much higher than the resistance of the transformer, resulting in very low real power losses (in watts), but some reactive power (vars).
Are shunt reactors used in nuclear reactors?
Answer 1. The only shunt reactors I know are used on transmission lines to alter power factor. This is nothing to do with the nuclear reactor in a power plant.Answer 2. I agree. Shunt reactors are use on transmission line and EHV to boost voltage, to generate VARs and for power factor correction.
What is the Reactive power in a capacitive modeand inducitive mode?
Generators can be required to generate real and reactive power. When operating in a leading mode, the generator is generating real and leading reactive power (inductive power). This means the generator is "sucking in VARS", which will pull down the terminal voltage similar to an inductor. It can also be operated in a lagging mode, which means it is generating real and lagging reactive power (capacitive power). The generator, then, is "pushing out VARS" like a capacitor, which will cause the terminal voltage to increase. Generators can only create so many leading and lagging VARs; in general lagging VARs are limited by the automatic voltage regulator output capabilities; leading vars are limitted by how much heat the stator can dissipate.
How do you reduce power factor value?
No-one ever aims to reduce the power factor, the ideal power factor is equal to 1, and that is the maximum possible value. A load with a power factor of 0.7 draws 40% more current along the supply wires compared to a equal-power load with a power factor of 1. That means that the power loss in the resistance of the supply wires is doubled in the case of the poor power factor. Since the supply company receives no extra revenue for the lost power, it does not like this situation and sometimes penalises users with poor power factors with extra tariffs. The power factor can often be improved by placing a passive reactor in parallel with the load to draw off the reactive volt-amps (VAR or kVAR) so that the supply wiring sees a load with a good power factor. Normally a bad load like a motor draws inductive VARs and in this case it can be corrected with a parallel capacitor that draws an equal number of capacitive VARs. Looked at another way, the added capacitor 'tunes' the load to resonate at the supply frequency.
What is the equivalent of voltage times ampere?
Volt Amperes is a measure of power; it is the vector sum of the real (in watts) and reactive (in vars) power.
When was Ellen Marie Vars born?
Ellen Marie Vars was born in 1957.
What is Vars-sur-Roseix's population?
Vars-sur-Roseix's population is 304.
What is the var meter?
A VAR Meter is used to measure Reactive Power in AC Circuits - Pure reactive components dissipate zero power, which makes sense in a DC circuit, as a capacitor passes no DC current and an inductor displaces no voltage. Yet, in an AC circuit, the reactive components "seem" to dissipate power, as current passes through the capacitor and the inductor sees a voltage drop. This counterfeit power is called "reactive power" and is measured not in Watts, but in VARs (Volt-Amps-Reactive). Its mathematical formula symbol is "Q". A VAR Meter is used to measure Reactive Power in AC Circuits - Pure reactive components dissipate zero power, which makes sense in a DC circuit, as a capacitor passes no DC current and an inductor displaces no voltage. Yet, in an AC circuit, the reactive components "seem" to dissipate power, as current passes through the capacitor and the inductor sees a voltage drop. This counterfeit power is called "reactive power" and is measured not in Watts, but in VARs (Volt-Amps-Reactive). Its mathematical formula symbol is "Q".
Why does a synchronous generator typically run at lagging power factor?
When a synchronous generator is running at lagging power factor the current it supplies lags its terminal voltage. Thus it acts as a source of reactive power, or magnetizing vars. Reactive power is needed to create the magnetic fields in devices such as transformers and induction motors. The Power factor of a utility depends on the type of load it supplies. Usually the Loads on utility are inductive loads (where the current lags behind the Voltage) and hence the power factor at which the utility operates is lagging. Most loads connected to utility are inductive loads like motors, fans, rolling mills which cause the power factor of the utility to be of lagging in nature.
What is the birth name of Henry Vars?
Henry Vars's birth name is Henryk Warszawski.
How does the power factors affect an electrical system?
Power factor is the real power (watts) divided by apparent power (the vector sum of real and reactive power). Reactive elements (things that have inductance or capacitance) cause phase shifts between voltage applied to them and current passing through them. This phase shift is a result of these elements holding power, then releasing it. Since these elements are not actually using power, this does not show up on your electric bill (unless you are billed on VARs as well as watts). Although they don't use real power, these reactive elements do cause "extra" current to flow, which the power company must supply. If this current is excessive (so you have a very low power factor) the power company must install oversized equipment to meet your demand; this means an added expense for them, with no payback on your electric bill. This is why power companies will often require a certain power factor be met, or bill you extra per kWh of use. Note power factor is a result of the load, not the other way around (a better question might be what is the a load's effect on power factor).
