Power Factor in Electrical system defines how efficiently Electrical power is being consumed.
The value of power factor varies from 0 to 1. Power factor 1 represent most efficient system while 0 power factor represents the least.
Low power factor is bad for both the power generating utility & power consumer.
As a consumer we need to pay for the total electricity bill which also includes the losses. Low the power factor means higher the losses.
As a power generating utility; Low power factor makes the losses higher which makes power delivery inefficient.
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| Name plate of 0.37 kW Induction motor with power factor 0.72 |
"To know better about the power factor you have to read some of the definition below"
DC system, Power=V*I
Where, V=Voltage & I=Current
Where, V=Voltage & I=Current
AC system(single phase), Power=V*I*cosΘ
Where, V=Voltage, I=Current & CosΘ= Power factor
"Only AC system contains the term power factor while DC system not. Because the DC power has constant fixed power supply while AC power contains periodic waveform changing continuously with respect to time which means AC power contains an angle in between voltage & current. Due to that angle in AC power, the power factor term exist only in AC system."
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| Voltage & Current waveforms in AC & DC |
Since Only AC power contains the term power factor while DC power not. That's why We will only talk about the AC system, Next.
THREE TYPES OF LOADS IN ELECTRICAL SYSTEM
- Resistive load
- Inductive load
- Capacitive load.
1. Resistive Load
The term Resistive is being derived from Resistance which means an oppose to the flow of electrical current. Resistive load has some specific resistance due to material composition which may change according to some conditions.
Ideally, Current & voltage both remains in phase in resistive load which means that current waveform exactly follows the voltage waveform without any delay. In such conditions Θ(the angle) becomes zero in between voltage & Current which results power factor becomes unity; cosΘ= cos0°=1.
Pure resistive case, AC Power becomes;
P=V*I*cosΘ
P=V*I*cos0°
P=V*I*1
P=V*I
P=V*I*cosΘ
P=V*I*cos0°
P=V*I*1
P=V*I
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| Both Current & Voltage are in phase| Sinusoidal AC waveform in Ideal Resistive load |
2. Inductive Load
Inductive load is basically a form of coil through which current flows. In Inductive coil, Wires are been bound onto each other which makes magnetic field of the wires to link with each other. That magnetic field linkage generates back emf in the coil.
Generated back emf actually opposes the change in flow of current which results current lags behind the voltage.
Ideally, Current lags behind the voltage by 90° in inductive load which results power factor becomes cosΦ=cos90°=0
Pure inductive case, AC power becomes;
P=V*I*cosΦ
P=V*I*cos90°
P=V*I*0
P=0
P=V*I*cosΦ
P=V*I*cos90°
P=V*I*0
P=0
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| Current lags behind the voltage by 90° (Electrical)| Sinusoidal AC waveform in Ideal Inductive load |
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| INDUCTIVE LOAD- Solenoid coil 6 watt 230VAC for pneumatic valve by JANATICS PNEUMATICS |
3. Capacitive load
Capacitive load consists of separated conductors & dielectric material sandwiched in between them. The dielectric material is poor conductor of electricity but excellent in storing electrical charge. Capacitive load stores power in the form of Electrostatic charge.
Ideally, Current leads the voltage by 90° in capacitive load which results power factor becomes
cosΦ= cos90°=0
cosΦ= cos90°=0
Pure Capacitive case, AC power becomes;
=V*I*cosΦ
=V*I*cos90°
=V*I*0
=0
=V*I*cosΦ
=V*I*cos90°
=V*I*0
=0
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| Current leads the voltage by 90° (Electrical)| Sinusoidal AC waveform in Ideal Capacitive load |
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| CAPACITIVE LOAD- Capacitor 8micro farad 440VAC,50Hz By EPCOS |
Conclusion of three types of loads
- Resistive loads having power factor equals to 1 represents the most efficient system in which delivered power is consumed in useful work completely. But that is the ideal case, In actual conditions, resistive load may also contains inductive or capacitive properties which results power factor may fall below 1.
- Inductive loads; in ideal case with zero power factor represents; total loss. In which non of the power is consumed in useful work. In practical case inductive loads also contains resistive & capacitive properties which makes power factor lie above zero.
- Capacitive loads; in ideal case; having power factor equals to 0 also represents the total loss in which non of the power is consumed in useful work. In practical case capacitive loads also contains resistive & inductive properties which makes power factor lie above zero.
- In practical conditions, Both the loads inductive & capacitive make the power factor fall below 1 but from both the sides it is opposite to each other As shown in an image below
- In inductive load, Power factor lags while in Capacitive load power factor leads. Lags & Leads are the angle displacement of current with respect to the voltage. Both the loads, Inductive & Capacitive counter to each other.
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| Scale shows lagging & leading power factor opposite to each other |
The answer is POWER TRIANGLE.
THREE TYPES OF POWERS IN POWER TRIANGLE IN ELECTRICAL SYSTEM
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| Power Triangle |
In Electrical System, There is three types of powers.
- Active/ Real Power
- Reactive Power
- Apparent Power
1. Active/ Real Power
It is the real, useful power consumed by loads. Active power is being represented in Watt.
[Active Power=VIcosΘ(1phase)]
WHERE- V is Voltage, I is Current & cosΘ is Power factor
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| Name Plate of Induction motor| Power shown in KW| |
2. Reactive Power
Reactive power is the phantom power That flows into the system That used to create magnetic field. Reactive power is being represented in VAR.
[Reactive Power= VIsinΘ(1phase)]
WHERE- V is Voltage, I is Current, sinΘ is reactive component
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| Name Plate of capacitor| Rating shown in KVAR| |
3. Apparent Power
It is the overall power or total power which is available from power generating utility. Apparent Power is being represented in KVA That's the reason rating of generators & transformers are being rated in KVA.
[Apparent Power=VI (1phase)]
WHERE- V is Voltage, I is Current
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| Name plate of transformer| Rating shown in KVA | |
- Apparent power is the total power which is available from power generating utility.
- Active/ Real power is consumption power which is consumed by electrical loads which directly participate in useful work.
- Reactive power is the imaginary power which flows in the circuit; used in creating magnetic field.
- (Apparent Power)²= (Active Power)² + (Reactive Power)²
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| Power triangle equivalent to right angled triangle | Right angled Triangle, A² + B² = C² Power Triangle, Q² + P² = S² |
UNDERSTANDING THE POWER FACTOR WITH AN EXAMPLE
We have 1KVA transformer with voltage ratio 230/110 Where primary voltage is 230V while secondary voltage is 110V.
Apparent Power= 1KVA=1000VA
Rated Current on Primary = Apparent power/primary voltage=1000/230= 4.34 Amps.
Rated Current on Secondary = Apparent power/secondary voltage=1000/110= 9.09 Amps.
Since load is going to be connect on secondary side that's why we will do the calculation on secondary side. On secondary side rated current is 9.09Amps which mean 9 Amps at secondary side of transformer is safe, At which transformer works safely under the safe limits of temperature, noise & Vibration.
EXAMPLE
Load(Active Power) 500Watt, Power factor 1 |
P=VIcosΘ
500=110*I*1
I=500/110
I=4.54 Amps
Load 500Watt, Power Factor 0.8(lagging)
P=VIcosΘ
500=110*I*0.8
I=500/(110*0.8)
I=5.68 Amps
Load 500Watt, Power factor 0.4(lagging)
P=VIcosΘ
500=110*I*0.4
I=500/(110*0.4)
I=11.36 Amps
We have seen in an example above the current consumption of same load goes on increasing as power factor decreasing. At 0.4 power factor, load produces excess burden on transformer which consumes 11.36 Amps which is higher than its rated current of 9.09 Amps.
That's why balancing the power factor is very important.
CONCLUSION
- Power Factor in Electrical system defines how efficiently Electrical power is being consumed.
- Power Factor is the ratio of real power to the apparent power.
- The value of power factor varies from 0 to 1.
- Power factor does not exist in DC while it exist in AC system only.
- Electrical system contains three types of loads Resistive, Inductive & Capacitive.
- Power factor is unity in resistive load, It lags in Inductive load while it leads in Capacitive load.
- Lead or lag is the angular displacement of current with respect to the voltage.
- Power triangle contains three types of powers- Apparent power, Real power & Reactive power.
- Apparent power is the total power available from power generating utility which is being rated as VA.
- Real power is the actual useful power consumed by electrical load which is being rated as Watt.
- Reactive power is the phantom power which flows in the circuit which is used in creating magnetic field. Units of reactive power is VAR.
- Capacitors are the source of reactive power while Inductors consumes reactive power.
Hope! post is helpful. If you have any doubt, suggestion or query please do comments.
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Power factor