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In Business & Finance, Home Electricity, Electronics Engineering, Electrical Engineering
Reactive power is an odd topic in AC (Alternating Current) power systems, and it's usually explained with vector mathematics or phase-shift sinewave graphs. However, a non-math verbal explanation is possible.

Note that Reactive power only becomes important when an "electrical load" or a home appliance contains coils or capacitors. If the electrical load behaves purely as a resistor, (such as a heater or incandescent bulb for example,) then the device consumes "real power" only. Reactive power and "power factor" can be ignored, and it can be analysed using an AC version of Ohm's law.

Reactive power is simply this: when a coil or capacitor is connected to an AC power supply, the coil or capacitor stores electrical energy during one-fourth of an AC cycle. But then during the next quarter-cycle, the coil or capacitor dumps all the stored energy back into the distant AC power supply. Ideal coils and capacitors consume no electrical energy, yet they create a significant electric current. This is very different from a resistor which genuinely consumes electrical energy, and where the electrical energy flows continously in one direction; moving from source to load.

In other words, if your electrical appliance contains inductance or capacitance, then electrical energy will periodically return to the power plant, and it will flow back and forth across the power lines. This leads to an extra current in the power lines, a current which heats the power lines, but which isn't used to provide energy to the appliance. The coil or capacitor causes electrical energy to begin "sloshing" back and forth between the appliance and the distant AC generator. Electric companies must install heavier wires to tolerate the excess current, and they will charge extra for this "unused" energy.

This undesired "energy sloshing" effect can be eliminated. If an electrical load contains both a coil and capacitor, and if their resonant frequency is adjusted to exactly 60Hz, then the coil and capacitor like magic will begin to behave like a pure resistor. The "energy sloshing" still occurs, but now it's all happening between the coil and capacitor, and not in the AC power lines. So, if your appliance contains a large coil induction motor, you can make the motor behave as a pure resistor, and reduce the current in the power lines by connecting the right value of capacitance across the motor coil.

Why is reactive power so confusing? Well, the math is daunting if not entirely obscure. And the concept of "imaginary power" puts many people off. But this is not the only problem. Unfortunately most of us are taught in grade school that an electric current is a flow of energy, and that energy flows back and forth in AC power lines. This is completely wrong. In fact the energy flows constantly forward, going from source to load. It's only the charges of the metal wires which flow back and forth.

Imagine that we connect a battery to a light bulb. Electric charges already present inside the wires will begin to flow in the circle, and then electrical energy moves almost instantly to the light bulb. The charge flow is circular like a belt, but the energy flow is one-way. Now imagine that we suddenly reverse the connections to the battery. The voltage and current will reverse... but the energy still flows in the same direction as before. It still goes from battery to bulb. If we keep reversing the battery connections over and over, we'd have an AC system. So, in an AC system, only the voltage and current are "alternating," while the electrical energy flows one-way, going from source to load. Where AC resistive loads are concerned, electrical energy does not "alternate." To understand energy flow in AC systems, it's critically important that we understand the difference between charge flow (current, amperes) and energy flow (power, watts.)

What is imaginary power? Simple: it's the unused power which flows backwards and forwards in the power lines, going back and forth between the load's coil or capacitor and the distant AC generator. If your appliance was a pure capacitor or inductor, then it would consume no electrical energy at all, but instead all the flowing energy would take the form of "sloshing energy," and we'd call it "imaginary power." Of course it's not actually imaginary. Instead it's reflected by the load.


What is real power? Even more simple: it's the energy flow which goes continuously from the AC generator and into the appliance, without any of it returning back to the distant generator.

Finally, what is "apparent" power? It's just the combination of the above two ideas: it is the continous-forward-moving or "real" energy flow, combined with the sloshing or "imaginary" energy flow.
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What is the definition of reactive power?

The definition of reactive power is power that is supplied from andAC circuit. This occurs when the voltage and current are not inphase.

Importance of reactive power?

So as to start the motor because reactive power helps create the magnetic fields in rotor.

What is the effecte of reactive power in generators?

The effect of reactive power in generators allows the generator tomaintain high voltage. Without the high voltage, the generator willbe faulty or will stop working.

What power of the courts is reactive?

Pronouncing judgment in a given criminal case is an example of areactive power that the courts do have. Interpreting the law to theaccused is another example.

What is reactive power and active power?

Active power is the power which is actually generated by generator. Reactive power is opposing power of active power ,which is created by load. For inductive loads reactive power is more, so we are using capacitor banks in system to improve power factor then reactive power decreases.

What is reactive power in power system?

Reactive power occurs in an AC system when it has a load with apoor power factor such as an induction motor. The power delivered is less than the voltage times the current by afactor called the power factor. The real power and the reactive power combine according toPythgoras, in other words if they are represented by two sides of aright-angle triangle, then the hypotenuse represents the volt-amps.In the equation kW is the power in kilowatts, kVAR is thekilovolt-amps of reactive power, and kVA is the kilovolt-amps: (kW) 2 + (kVAR) 2 = (kVA) 2

What is the unit of measure for reactive power?

Volt Amps [volts times amps] is used for reactive and apparent power. Watts (dimensionally the same as volt amps) is used to indicate real power. Answer Reactive power is measured in reactive volt amperes ( var ).

Unit of reactive power?

Reactive power is measured in reactive volt amperes (var). Note that this is a 'traditional unit', as SI doesn't recognise anything other than the watt -regardless of the 'type' of power!

What is Reactive power of power system?

Reactive power is mainly used by big industries. To put it simply,things which store energy like capacitors and inductors take inenergy then let it out as the ac voltage supply changes. Thevoltage is largely unafected, but the maximum currents required bythe system is increased. Short---- More current is required with reactive power, and thisincreases running costs. Most networks are inductive, and addingcapacitors balences the system out. Big industries are charged forreactive power used but domestic users aren't. (note, reactivepower is only relavent to ac circuitry and networks, not dc)

Is reactive power a vector or scalar?

I am not sure what exactly you mean by "reactive power" (I guess you mean electrical reactive power), but power is the ratio of energy for a period of time. So that makes power (and reactive power as well) a scalar, since you can describe it with only one number. The fact that electrical reactive power is drawn on a XY plane, should not confuse you.

What is reactive power in electrical system?

It is product of Current,Voltage and Sin angle between current and voltage. Reactive Power = Current(I)*Voltage(V)*Sin(angle B/W Voltage and Current) It is also know as the power used in transformation of energy in one form to another form. Answer Reactive power is the rate at which energy is alternately stored in a magnetic or electric field and returned to the supply of an AC circuit, and is expressed in reactive volt amperes. Reactive power is associated with inductive or capacitive loads. The vector sum of reactive power and true power (watts) is called the apparent power (volt amperes) of the circuit.

Why is there no power consumed in reactive components?

While it seems there is no power consumed in reactive components, the reality is that there is power transfer, which must be considered in the system design. Power is amperes times volts, but in a reactive circuit, the two are not in phase. If the phase angle becomes 90 degrees (a power factor of zero) the effect will be the appearance of zero power. Supplement . Consider the transformer for a start. The magnetic susceptibility curve for the transformer core forms a hysteresis loop. That S-shaped diagram you remember. The area inside the loop is power lost in the system, and goes to make the transformer a little warm. the same applies to any inductor. And there is always a small resistive loss in the copper wire as well. (Unless you have a super-conductor and some liquid helium to hand.) The capacitor is next. It works by storing the energy as a distortion of the "crystal matrix" of the dielectric material. Which is not as lossy as the iron core of an inductor, but does have some loss. In closing, the transformer reflects to the supply side, the reactance of the whole circuit as seen by the secondary side.

How do you control reactive power?

I assume the question is how do you control power factor; if I'm wrong, forgive me. When the amount of reactive power compared to real power increases, the power factor decreases. To bring the power factor back to unity (ie 100% real power, 0 reactive), reactive elements must be included in the system to counteract the inherent reactivity of the system. This typically is done by adding capacitor banks electrically near load, because the power system typically has inductive reactive power. There are other available technology to do this, such as Dynamic VAR controllers, but are much more expensive than your typical cap bank for their size. These are essentially power transistors forced to operate in such a way as to appear as variable capacitors / inductors.

What is the use of active power and reactive power in power plant?

so we have electrcity oh and my friend Cody is a power house lol he stinks and drew he funny and i have a friend george who lies everyday about 24/7 he could power it with his lies

What is the power dissipated by a reactive load?

No power is dissipated by a load composed exclusively of either capacitive or inductive reactance.

What is the use of reactive power?

Reactive power is used to transfer power system (instead of dipping voltage at one end as is necessary with DC). It is also used for voltage control. If voltage support is needed, capacitors banks are often installed - these cause the voltage to increase. On very high voltage power lines, it is often a practice to install inductors, because the line charging current (ie current due to the capacitive effect of the line to ground) can cause the voltage to increase beyond design specification. These help bring the voltage down into tolerance.

What is the definiton of reactive power?

Power where the voltage and current are not in phase (specifically, they are 90 degrees out of phase with eachother).

What is the role of reactive power in a power system?

To supply the reactive power demand of load and to regulate of output volage at the grid

Why reactive power is so confusing for engineers?

This is because reactive power concept is completely different from active(real) power, That is when we talk about active ( real ) power , we deal with two terms :. The average value, and the instantaneous value. Both has significant values; let's say the average value is 5kw, where the instantaneous value maybe 2kw or 6kw, etc... On the otherhand, reactive power has always a Zero average value, and a different significant instantaneous values, but since the instantaneous value is difficult to measure, we always take the maximum instantaneous value of reactive power and deal with it as a textbook terminology ( Reactive power ) which is symbolized as Q and equals V I sin theta . And for the same reason (difficult to measure instantaneous value ) we easily deal with the average value of the active power other than the instantaneous value. As a brief: ( Active power ) symbolized P or known sometimes as real power equals V I cos theta represents the average value. ( Reactive power ) symbolized Q equals V I sin theta represents maximum instantaneous value. Someone can ask! Why not to take the maximum instantaneous value of average power such as reactive power as a terminology? Easily , why not to unites the two concepts ?! This is the answer of our main question (Why reactive power is so confusing for engineers?) This is easily because ,there is no useful meaning of using the instantaneous value for the active power, because it is a real produced power goes in one direction from source to load, where the average reactive power is always zero valued, since it goes back and forth in the network, and we are forced to deal with it in some way as an indication value and give it a unique terminology to express it as a fact that we cannot skip. In other words, you cannot compare two different things; apple and banana! Each one has a different taste. I hope that I answered the question, and dislodged some dust about this confusing concept, even I didn't take the boring mathematical path.

Why is reactive power so confusing to understand?

This is because reactive power concept is completely different from active(real) power, That is when we talk about active ( real ) power , we deal with two terms : The average value, and the instantaneous value. Both has significant values; let's say the average value is 5kw, where the instantaneous value maybe 2kw or 6kw, etc... On the otherhand, reactive power has always a Zero average value, and a different significant instantaneous values, but since the instantaneous value is difficult to measure, we always take the maximum instantaneous value of reactive power and deal with it as a textbook terminology ( Reactive power ) which is symbolized as Q and equals V I sin theta . And for the same reason (difficult to measure instantaneous value ) we easily deal with the average value of the active power other than the instantaneous value. As a brief: ( Active power ) symbolized P or known sometimes as real power equals V I cos theta represents the average value. ( Reactive power ) symbolized Q equals V I sin theta represents maximum instantaneous value. Someone can ask! Why not to take the maximum instantaneous value of active power such as reactive power as a terminology? Easily , why not to unites the two concepts ?! This is the answer of our main question (Why reactive power is so confusing to understand?) This is easily because ,there is no useful meaning of using the instantaneous value for the active power, because it is a real produced power goes in one direction from source to load, where the average reactive power is always zero valued, since it goes back and forth in the network, and we are forced to deal with it in some way as an indication value and give it a unique terminology to express it as a fact that we cannot skip. In other words, you cannot compare two different things; apple and banana! Each one has a different taste. I hope that I answered the question, and dislodged some dust about this confusing concept, even I didn't take the boring mathematical path.

Why reactive power is named as reactive?

Actually reactive power is a power which flows in between load to source which is a reactive action of the power given from source to load.the given power to load will not be utilised fully.some power will be oscillating from load to source.this is called reactive power.

What is the effect of frequency on reactive power?

This is not really a practical question because power systems runat an almost constant frequency. But for equipment that runs with alagging power factor, like induction motors, the presence ofinductance in the motor windings means that the reactance would goup and the power factor down with increasing frequency. So thereactive power would increase relative to the real power.

How reactive power is generated?

Every electric loads that works with magnetic fields(i.e: motor,chokes,transformers,inductive heating,arc-welding generators etc)produces a varying electric lags which is called INDUCTANCE .The lag of inductive loads maintain the current sense(eg: Positive) for some time and the negative going voltage tries to reverse it.These phase shift between current and voltages have to be maintained.The current and voltage have opposite sign.During this time the negative power or energy is fed to the network/circuit.When current and voltages have same sign again,the same amount of energy is required to built up the magnetic field in inductive loads. This magnetic reversal energy is called Reactive power .In AC circuit (50 Hz - 60 Hz) this process repeated 50 to 60 times a second.So an obvious solution is to briefly store the magnetic reversal energy in capacitor and relieve the network (the supply line)of this reactive energy.

What is real power and reactive power?

'Real', 'active', or 'true' power describes the rate at which a load does work or dissipates energy by heat transfer. This represents a permanent loss of energy from the supply. 'Reactive' power describes the rate at which energy is alternately stored in a load's magnetic or electric field, and returned to the supply every quarter cycle. True power is measured in watts, and reactive power is measured in reactive volt amperes.

Why reactive power flow is undesired?

Reactive power is useless part of the energy supplied. A minimum value of reactive power is always required to keep the voltage constant and supply the useful active power. In order to understand the concept completely, do refer PV and QV curves which explains the interdependency of active power, reactive power and voltage.

What is real power and reactive power in power systems?

Real power is power that is used to do work. This is the power a light bulb uses to glow. Reactive power is power that is stored in one part of the AC voltage wave, and released in another. This causes the power to appear as a phase shift, and is generally caused by inductive or capactive loads. With regard to the power system, you can also get reactive power flowing due to unequal source voltages. Under these conditions, the apparent impedance of one source to the other will appear reactive/inductive, resulting in reactive power flow.

Why reactive power is important?

it is important b'cos,it discribes the losses of power.For caliberation we are giving more prieority to the loss in the component or a device

How do you determine reactive power in three phase?

Real power (W, watts) is apparent power (VA, volt-amperes), times power factor. Power factor is the cosine of the phase angle between voltage and current. For a resistive load, such as a toaster, power factor is unity, so W is VA. For an inductive load, such as a motor, with a (typical) power factor of 0.92, W is VA times 0.92. Also, in terms of reactive power, real power (W) is reactive power (VAR) times the reactive power factor, which is the sine of the phase angle between voltage and current. To clarify "true", "apparent", and "reactive" power, the phasor sum of VA and VAR is equal to W. Think of the unit circle, where zero degrees is resistive, generally shown as north. For the example case of the inductive load at 0.92 power factor, the angle of the phase angle is -23 degrees, or typically shown as 337 degrees. VA in this case, if W equals 10000, is 9200, while VAR is -3919 . Phase has nothing to do with the equation, since you need to consider each phase on its own merits, and add up the results. However, do not forget that you need to be consistent, in that you always use star or delta voltage. If you switch systems, star to delta or delta to star, don't forget the 1.732 (square root of 3) factor in the calculations.

How does reactive power change the Power Factor?

Power Factor is the relationship between the phase of the current and voltage which are each sine waves. When there is an inductance in a circuit the AC current waveform tends to lag the voltage. This causes a phase difference which reduces the Power Factor from a maximum of one to something less.

What are advantages of reactive power?

1.electric motors need reactive power to generate magnetic field for their operation... 2.reactive power is advantageous to control the voltage sag..

Why power rating of capacitor is reactive in nature?

A capacitor is composed of metal plates. Voltage is applied to one, which causes electrons to build up on the other. This is reactive in nature, thus a capacitor is reactive. It stores a charge, and releases this charge when the voltage decreases.

How reactive power helps in power transfer?

Reactive power does not help, it causes the amunt of current to behigher than necessary and the transmission losses to be higher thannormal.

What is meant by the active and reactive powers in electricity?

These terms describe the behaviour of energy in alternating-current circuits. Active power (also known as ' true power ' or ' real power ') describes the rate at which energy is permanently dissipated by the resistive component of a circuit or load. Active power is measured in watts. Reactive power describes the rate at which energy is alternately stored in the magnetic or electric field and, then, returned to the source when the field collapses, during every quarter-cycle. Reactive power is measured in reactive volt amperes. Apparent power is the vector sum of a circuit's active and reactive power, and is measured in volt amperes. The apparent power of an a.c. load can be determined from the product of a voltmeter and an ammeter reading. The active power can be determined by using a wattmeter. The reactive power can then be determined by vector subtraction.

Why does not wattmeter measure the reactive power?

A wattmeter is designed so that it measures the supply voltage and the in-phase component of the load current. The product of these two quantities is the true power of the load.

Can reactive power be used to power a bulb?

The 'type' of power is determined by the load. If the load is resistive (e.g. a lamp) then the rate at which it consumes energy is termed 'true power', expressed in watts. You seem to be under the impression that reactive power is 'pushed out' into a load. This is quite false; the load determines the power.

How reactive power drives active power?

reactive power depends on motor winding losses and the reason for increasing of temperature. At running condition the motor power reduces by copper loss.

Why there is no reactive power in DC system?

In case of dc there is no reactive components and current drawn from the supply is in phase with the voltage.due to absence of inductor and capacitor the reactive power demand in dc is zero.

How reactive power is utilised and returned to the circuit?

The energy is stored in an inductor in the form of magnetic field and in capacitor as electric charges. In both cases, as the current increase,according to its sine wave form, the flux or electric charges build up i.e energy being stored. As the current start dropping the field or electric charge start dropping too thus energy is being fed back into the circuit.

What is reactive power and its significance?

' Reactive power ' is the rate at which energy is stored in an electric or magnetic field, and returned to the supply. To differentiate between reactive power and true power (the rate of heat transfer and of work), and for no other reason, it is expressed in reactive volt amperes (var) rather than in watts (W). Its significance is that it is necessary to establish and sustain electric and magnetic fields.

What is reactive power in three phases system?

Reactive power is the rate at which energy is alternately stored within, and returned from, electric or magnetic fields set up within an electric circuit, and is expressed in reactive volt amperes.

Is that the reactive power is a combination of both reactive power and imaginary power?

No. It is apparent power (expressed in volt amperes) that is the combination (vector sum) of true power (expressed in watts) and reactive power (expressed in reactive volt amperes). 'Imaginary power' is simply another name for 'reactive power' -where 'imaginary' is simply mathematicians-speak for 'quadrature' or 'right angles'.

What is reactive power and where or how it dissipates?

Reactive power is power created by inductive or capacitive elements in AC systems. A long power transmission line is effectively a wire at a voltage some distance away from ground. A simple capacitor is the same thing - a metal plate, with an air gap between the electrodes. Thus an energized power line can be drawn as a big capacitor in parallel with a resistor which is in series with an inductor (the transmission line has natural resistance and inductance). When it is lightly loaded, the capacitance of this line will supply reactive power to the system, causing the voltage to increase. When more power flows down the line, the inductance of the line will "use" this reactive power and cause the voltage to decrease. In short, capacitors make reactive power, and inductors dissipate it. Generators also can create or consume reactive power. Answer ' Reactive power ' describes the behaviour of part of the energy supplied to a circuit from an a.c. source, and is the rate at which that energy is alternately stored, then released, within a magnetic or electric field. Unlike ' true power ' (which describes the rate at which is permanently lost by doing work or through heat transfer) there is no net loss of energy from the supply due to reactive power. To quote one textbook, 'reactive power represents the rate at which energy sloshes back and forth between the source and the load each quarter-cycle'.

How can reactive power be reduced?

Reactive power from a generator can be reduced by reducing the terminal voltage (or changing taps on the step up transformer), or reducing the field current. Switching out lightly loaded lines and using parallel reactor banks on transmission systems will reduce the available reactive power. If what you are meaning is how can the reactive power used by a machine be reduced, that's a different topic and will depend on the machine. Usually the reactive requirements of a machine are not modified (which would require physical changes to the machine), but extra reactive power is added to the system in the form of parallel capacitors.

Why reactive power not useful?

Reactive power is useful, just not useful in doing real work. Another answer It's unfortunate that we use terms, such as 'imaginary power' and 'useful power' to describe reactive power and true power. This is because these terms are not being used in their 'everyday' sense! For example, 'imaginary power' doesn't mean that it exists only in the mind, or that only true power is 'useful'. These terms are used by mathematicians to differentiate between the horizontal axis and the vertical axis when describing vectors or phasors or, in this case, the so-called 'power triangle', in which reactive power is drawn at right angles ('imaginary') to true power. So, as the original answer says, reactive power is indeed 'useful' (for example, it is essential for supporting magnetic or electric fields).

What meaning by reactive power compensation?

A reactor in series with a motor will reduce starting current it can be shorted out after the motor gets near synchronous speed some motors have a rotor with two squirrel cages the outer on has longer higher resistance bars the inner heavier lower resistance bars which will do the same thing but with a bit more feedback with respect to actual motor speed for the softer starts and without external sensors or timers or if i didnt understand the question you may be charged more $$ for reactive load if you plants has lots of running unloaded motors and transformer ballasts for florescent lamps you facility will be paying for imaginary power you put capacitors in parallel with the incoming power to get the near unity power factor the power company likes

Can you transfer power without reactive power?

I'm not sure the question makes sense. In a word, "yes". Think of a simple DC source and a resistor. No reactive power there, but power is being dissipated by the resistor ("transferred" from the DC source). If you're talking about AC circuits and "transferring" means going through a transformer, then, again, "yes" because whatever reactance the transformer has can be offset by a capacitor with the same. So you would have no reactive power, but power would be transferred.

How can you reduce reactive power?

If, for example, the reactive power of a load is due to its inductance, then installing a capacitor in parallel with the load will reduce the overall reactive power.

Why does capacitor supply reactive power?

A capacitor needs current to flow into and out of it before avoltage is developed across it, so in an ac circuit the current ina capacitor is 90 degrees or a quarter-cycle in front of thevoltage. In a 50 Hz system the cycle period is 20 milliseconds sothe current peak is 5 milliseconds before the voltage peak everytime. The energy in the capacitor is the charge times the voltage, andenergy flows into the capacitor and back into the supply twice percycle. No net energy is dissipated in the capacitor. All the energyis reactive, in other words it flows in and out. The power-factorof the capacitor seen as a load is zero. .

Do reactive component of impedance dissipate power?

The reactive part dissipates no power because in a reactor thecurrent is 90 degrees out of phase with the voltage. The effect of this is that any power that leaves the generator onone quarter-cycle comes back to the generator on the next. The netpower is zero.

How is the reactive power useful?

Reactive power (VARS) is required to maintain the voltage todeliver active power (watts) through transmission lines. . Motor loads and other loads require reactive power to convertthe flow of electrons into useful work. . When there is not enough reactive power, the voltage sags downand it is not possible to push the power demanded by loads throughthe lines.