Explain the terms of reactive power, complex power,active power and power factor
Answers
Answered by
10
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) .
Complex Power
Complex power is “the complex sum of real and reactive powers”. It is also termed as apparent power, measured in terms of Volt Amps (or) in Kilo Volt Amps (kVA). The rectangular power of complex power is given below:
S=P+jQ
Where, S is complex or apparent power, P is real power measured in terms of Watts and Q is reactive power measured in terms of Volt Amps Reactive (generally in kVAR).
Moreover, the complex power has magnitude and phase angle. The polar form of complex power is given below:

Where, the real power is produced by linear component, P =VI cos φ and the reactive power is produced by non-linear components, Q =VI sin φ.
In addition, the complex power for transformer can be written as, S=VI.
The complex power for transmission lines is, S=VI*, where I* is complex conjugate of current.
.
POWER FACTOR.
Power factor is the ratio between the kW and the kVA drawn by an electrical load where the kW is the actual load power and the kVA is the apparent load power.
Simply, it is a measure of how efficiently the load current is being converted into useful work output and more particularly is a good indicator of the effect of the load current on the efficiency of the supply system.
Consider this:
When you buy fuel for a vehicle, the manufacturer makes in it in litres, the pump dispenses it in litres and you pay for it in litres. £/litre – simple!
When you buy potatoes, the supplier bags them in kilos the shop sells them in kilos and you pay for them in kilos. £/kg – simple!
When you buy electricity, the “manufacturer” (electricity generator) makes kVA (kilo volt amperes) and you pay for it in kWh (kilowatt hours) or maybe on your bill (Units) – not so simple!
Maybe we all should have kVA meters to make life simple.
So what is the kilowatt hour (or unit) we get on our bills? Simply, 1000 watts of electricity being used for 1 hour.
Example: 10 x 100 watt lamps x 1 hour=1000 watts/hr divided by 1000=1kWh – simple!
Now here comes the problem: In an alternating current (AC) electrical supply, a mysterious thing called “Power Factor” comes into play. Power Factor is simply the measure of the efficiency of the power being used, so, a power factor of 1 would mean 100% of the supply is being used efficiently. A power factor of 0.5 means the use of the power is very inefficient or wasteful.
So what causes Power Factor to change? In the real world of industry and commerce, a power factor of 1 is not obtainable because equipment such as electric motors, welding sets, fluorescent and high bay lighting create what is called an “inductive load” which in turn causes the amps in the supply to lag the volts. The resulting lag is called Power Factor.
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) .
Complex Power
Complex power is “the complex sum of real and reactive powers”. It is also termed as apparent power, measured in terms of Volt Amps (or) in Kilo Volt Amps (kVA). The rectangular power of complex power is given below:
S=P+jQ
Where, S is complex or apparent power, P is real power measured in terms of Watts and Q is reactive power measured in terms of Volt Amps Reactive (generally in kVAR).
Moreover, the complex power has magnitude and phase angle. The polar form of complex power is given below:

Where, the real power is produced by linear component, P =VI cos φ and the reactive power is produced by non-linear components, Q =VI sin φ.
In addition, the complex power for transformer can be written as, S=VI.
The complex power for transmission lines is, S=VI*, where I* is complex conjugate of current.
.
POWER FACTOR.
Power factor is the ratio between the kW and the kVA drawn by an electrical load where the kW is the actual load power and the kVA is the apparent load power.
Simply, it is a measure of how efficiently the load current is being converted into useful work output and more particularly is a good indicator of the effect of the load current on the efficiency of the supply system.
Consider this:
When you buy fuel for a vehicle, the manufacturer makes in it in litres, the pump dispenses it in litres and you pay for it in litres. £/litre – simple!
When you buy potatoes, the supplier bags them in kilos the shop sells them in kilos and you pay for them in kilos. £/kg – simple!
When you buy electricity, the “manufacturer” (electricity generator) makes kVA (kilo volt amperes) and you pay for it in kWh (kilowatt hours) or maybe on your bill (Units) – not so simple!
Maybe we all should have kVA meters to make life simple.
So what is the kilowatt hour (or unit) we get on our bills? Simply, 1000 watts of electricity being used for 1 hour.
Example: 10 x 100 watt lamps x 1 hour=1000 watts/hr divided by 1000=1kWh – simple!
Now here comes the problem: In an alternating current (AC) electrical supply, a mysterious thing called “Power Factor” comes into play. Power Factor is simply the measure of the efficiency of the power being used, so, a power factor of 1 would mean 100% of the supply is being used efficiently. A power factor of 0.5 means the use of the power is very inefficient or wasteful.
So what causes Power Factor to change? In the real world of industry and commerce, a power factor of 1 is not obtainable because equipment such as electric motors, welding sets, fluorescent and high bay lighting create what is called an “inductive load” which in turn causes the amps in the supply to lag the volts. The resulting lag is called Power Factor.
Similar questions