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What is the relation between the active power and reactive power? How can we change the reactive power to active power?

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Question added by hassan qutb , Facility&Engineering Manager PMP. , مقاولات خاصه
Date Posted: 2013/11/26
muhammad arif
by muhammad arif , Assistant Engineer , Phoenix armour

 (1) Real Power: (P)  Alternative words used for Real Power (Actual Power, True Power, Watt-full Power, Useful Power, Real Power, and Active Power) In a DC Circuit, power supply to the DC load is simply the product of Voltage across the load and Current flowing through it i.e., P = V I. because in DC Circuits, there is no concept of phase angle between current and voltage. In other words, there is no Power factor in DC Circuits. But the situation is Sinusoidal or AC Circuits is more complex because of phase difference between Current and Voltage. Therefore average value of power (Real Power) is P = VI Cosθ is in fact supplied to the load. In AC circuits, When circuit is pure resistive, then the same formula used for power as used in DC as P = V I.  You may also read about Power Formulas in DC, AC Single Phase and and AC Three Phase Circuits. Real Power formulas: P = V I                                  (In DC circuits) P = VI Cosθ                          (in Single phase AC Circuits) P = √3 VL IL Cosθ         or     (in Three Phase AC Circuits) P =3 VPh IPh Cosθ  P = √ (S2 – Q2) or P =√ (VA2 – VAR2) or   Real or True power = √ (Apparent Power2 – Reactive Power2) or kW = √ (kVA2 - kVAR2)   (2) Reactive Power: (Q)   Also known as (Use-less Power, Watt less Power) The powers that continuously bounce back and forth between source and load is known as reactive Power (Q) Power merely absorbed and returned in load due to its reactive properties is referred to as reactive power The unit of Active or Real power is Watt where1W =1V x1 A. Reactive power represent that the energy is first stored and then released in the form of magnetic field or electrostatic field in case of inductor and capacitor respectively. Reactive power is given by Q = V I Sinθ which can be positive (+ve) for inductive, negative (-Ve) for capacitive load. The unit of reactive power is Volt-Ampere reactive. I.e. VAR where1 VAR =1V x1A. In more simple words, in Inductor or Capacitor, how much magnetic or electric field made by1A x1V is called the unit of reactive power. Reactive power formulas: Q = V I Sinθ Reactive Power =√ (Apparent Power2- True power2) VAR =√ (VA2 – P2) kVAR = √ (kVA2 - kW2)   (3) Apparent Power: (S) The product of voltage and current if and only if the phase angle differences between current and voltage are ignored. Total power in an AC circuit, both dissipated and absorbed/returned is referred to as apparent power The combination of reactive power and true power is called apparent power In an AC circuit, the product of the r.m.s voltage and the r.m.s current is called apparent power. It is the product of Voltage and Current without phase angle The unit of Apparent power (S) VA i.e.1VA =1V x1A. When the circuit is pure resistive, then apparent power is equal to real or true power, but in inductive or capacitive circuit, (when Reactances exist) then apparent power is greater than real or true power.  Apparent power formulas: S = V I Apparent Power = √ (True power2 + Reactive Power2) kVA = √kW2 + kVAR2 Also Note that; Resistor absorbs the real power and dissipates in the form of heat and light. Inductor absorbs the reactive power and dissipates in the form of magnetic field

Capacitor absorbs the reactive power and dissipates in the form of electric or electrostatic filed

   These all quantities trigonometrically related to each other as shown in below figure.                                                            Click image to enlarge Power Triangle For more Clearance and explanation., i used Lays Chips  and Beer Analogy for Real or True Power, Reactive Power , Apparent power and power factor Lays Chips  Analogy of Real or True Power, Reactive Power, Apparent power & power factor                                                           Click image to enlarge       power trangle, real true reactive apparent power lays chips analogy for power factor

     Beer Analogy of Active or True power, Reactive power, Apparent Power and Power factor. 

  Beer Analogy of Active or True power, reactive power, Apparent Power and Power factor. 

 

Leonardo Banzali
by Leonardo Banzali , Electrical Maintenance-trainer , Sadara Chemical Company

For the relationship between active power and reactive power, basing on the common power factor angle of a system represented by the symbol "ϴ" common to both power we can say that their relationship can be referred to the following formulas: (Same on single phase or three phase)

Active power (Resistive) P = Volts (V) x Current (I) x Cosine ϴ

Reactive power (Inductive or Capacitive) P = Volts (V) x Current (I) x Sine ϴ

However we cannot change reactive power to active power because they are of different criteria in power (based on Power Triangle). Active power is based on true and  resistive load quantities while Reactive power is based on inductive or capacitive load quantities in the electrical systems.

Mohammed abdu ahmed  Alraeeini
by Mohammed abdu ahmed Alraeeini , رئيس قسم الكهرباء , عالم الرؤية لانظمة الطاقة الشمسية

We know that reactive loads such as inductors and capacitors dissipate zero power, yet the fact that they drop voltage and draw current gives the deceptive impression that they actually do dissipate power. This “phantom power” is called reactive power, and it is measured in a unit called Volt-Amps-Reactive (VAR), rather than watts. The mathematical symbol for reactive power is (unfortunately) the capital letter Q. The actual amount of power being used, or dissipated, in a circuit is called true power, and it is measured in watts (symbolized by the capital letter P, as always). The combination of reactive power and true power is called apparent power, and it is the product of a circuit's voltage and current, without reference to phase angle. Apparent power is measured in the unit of Volt-Amps (VA) and is symbolized by the capital letter S.

As a rule, true power is a function of a circuit's dissipative elements, usually resistances (R). Reactive power is a function of a circuit's reactance (X). Apparent power is a function of a circuit's total impedance (Z). Since we're dealing with scalar quantities for power calculation, any complex starting quantities such as voltage, current, and impedance must be represented by their polar magnitudes, not by real or imaginary rectangular components. For instance, if I'm calculating true power from current and resistance, I must use the polar magnitude for current, and not merely the “real” or “imaginary” portion of the current. If I'm calculating apparent power from voltage and impedance, both of these formerly complex quantities must be reduced to their polar magnitudes for the scalar arithmetic.

There are several power equations relating the three types of power to resistance, reactance, and impedance (all using scalar quantities):

Please note that there are two equations each for the calculation of true and reactive power. There are three equations available for the calculation of apparent power, P=IE being useful only for that purpose. Examine the following circuits and see how these three types of power interrelate for: a purely resistive load in Figure belw, a purely reactive load in Figure belw, and a resistive/reactive load in Figure belw.

Resistive load only:

True power, reactive power, and apparent power for a purely resistive load.

Reactive load only:

True power, reactive power, and apparent power for a purely reactive load.

Resistive/reactive load:

True power, reactive power, and apparent power for a resistive/reactive load.

These three types of power -- true, reactive, and apparent -- relate to one another in trigonometric form. We call this the power triangle: (Figure belw).

Power triangle relating appearant power to true power and reactive power.

Using the laws of trigonometry, we can solve for the length of any side (amount of any type of power), given the lengths of the other two sides, or the length of one side and an angle.

  • REVIEW:
  • Power dissipated by a load is referred to as true power. True power is symbolized by the letter P and is measured in the unit of Watts (W).
  • Power merely absorbed and returned in load due to its reactive properties is referred to as reactive power. Reactive power is symbolized by the letter Q and is measured in the unit of Volt-Amps-Reactive (VAR).
  • Total power in an AC circuit, both dissipated and absorbed/returned is referred to as apparent power. Apparent power is symbolized by the letter S and is measured in the unit of Volt-Amps (VA).
  • These three types of power are trigonometrically related to one another. In a right triangle, P = adjacent length, Q = opposite length, and S = hypotenuse length. The opposite angle is equal to the circuit's impedance (Z) phase angle.

nelson arul raj
by nelson arul raj , Project Manager , Aesthetix media LLc

reactive power definition

aternative words for real power - actual power/true power/ active power

reactive power also known as use less power/ watt less power 

The power that continuously bounceback and forth between source and load is referred as reactive power

The power between source and load is real power

we cannot convert ctive power to reactive power

 

 

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