Power Factor

In Ideal conditions, System’s produces 100% output without any loss. But in real world, Losses are there Which make lowers the overall efficiency.

Electrical machines takes Electrical power at standard rating. & then it produces the output in along with some losses. For example, “When an Electrical transformer is get connected to a power supply, The primary winding produces an electromagnetic field. This field links with the secondary winding. Due to induction, EMF get generated in secondary winding. Both the winding contains the losses known as core loss & copper loss.

The written presentation-"Core losses are fixed losses which appears in stamping of Electromagnet due to induction.

Copper losses are variable losses which appears across the winding. Copper losses are current & resistance dependent."

Similarly, We are getting electrical power from power generating utilities. They charge us based on total energy intake, which also includes the losses.

The Electrical power intake from power generation utility is; AC . AC power moves with respect to time & changes directions at fixed intervals, That’s why term frequency exist in AC .

GIf representing Sinusoidal ac waveform — **GIF** representing Sinusoidal ac waveform

When sinusoidal voltage waveform get applied across the load. A current starts flowing through the circuit. The current waveform actually depends on the type of load. It may follow the same sinusoidal form as the voltage or it may get distorted. The distorted current waveform produces losses in the system. This distorted impact of waveform is represented through a term “POWER FACTOR“.

In an image below, Current waveform on 2 different loads on same AC voltage is been shown. Behavior of both the current is entirely different to each other.

A presentation shows the current waveform of different load on same AC voltage waveform — Current waveform on 2 different loads on same AC voltage

“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 the 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. Lower the power factor, higher the losses.
As a power generating utility; Low power factor makes the losses higher which makes power delivery efficiency lower.

Name plate of 0.37 kW Induction motor with power factor 0.72

To know more about power factor, We should go through some of the definitions below :

(DC) DIRECT CURRENT

Direct current remains constant through out the time. It do not change its direction. That’s why an angular term do not exist in between Voltage & current.

DC power totally depend upon the product of voltage & current.

DC Power=V*I
Where, V=Voltage & I=Current

(AC) ALTERNATING CURRENT

Alternating current continuously changes its direction with respect to time. That’s why an angular term exist in between voltage & current. AC power depend upon 3 parameters- Voltage, Current & Power factor.

AC system(single phase), Power=V*I*cosΘ

Where, V=Voltage, I=Current & CosΘ= Power factor

Since Only AC power contains the term power factor while DC power don’t. That’s why We will only talk about the AC power, Next.

THREE TYPES OF LOADS IN ELECTRICAL SYSTEM

There are; in total; three types of Electrical Loads. Circuits are designed through the combination of these three loads. Three loads are :

Resistive load
Inductive load
Capacitive load.

1. Resistive Load

The term Resistive is being derived from the term Resistance which means an element opposing the flowing of electrical current. Resistive load has some specific resistance due to material composition which may get 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, without any angle in between them. 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

Sinusoidal AC waveform in Ideal Resistive load

2. Inductive Load

Inductive load is basically a form of insulated coil through which current flows. In Inductive load, Wires are been bound onto each other which makes magnetic field of the wires linking 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

Sinusoidal AC waveform in Ideal Inductive load

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

Pure Capacitive case, AC power becomes;
=V*I*cosΦ
=V*I*cos90°
=V*I*0
=0

Sinusoidal AC waveform in Ideal Capacitive load

CAPACITIVE LOAD- Capacitor 8micro farad 440VAC,50Hz By EPCOS

Conclusion of three types of loads

Resistive loads is having power factor equals to 1 which 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; zero power consumption. 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 load; in ideal case; with zero power factor, zero power consumption. In practical case Capacitive load also contains some resistive & inductive properties which makes power factor lie above zero.

POWER FACTOR SCALE

In practical conditions, Both the loads inductive & capacitive make the power factor fall below 1. But both the loads Inductive & Capacitive are 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.

Scale shows lagging & leading power factor opposite to each other

In the top most image above, the power factor of induction motor is 0.72 which means that 72% Power is consumed in useful work but the question is where is 28% which does not participate in useful work.

The answer is POWER TRIANGLE.

POWER TRIANGLE IN ELECTRICAL SYSTEM

Power Triangle

In Electrical System, There are three types of powers. Active power, Reactive power & Apparent power. The arrangement of these three powers around the right angle triangle is known as Power triangle. Next, All these powers are going to be discussed one by one.

1. Active/ Real Power

It is the real, useful power consumed by loads which contains the term power factor. Active power is being represented in Watt.

[Active Power=VIcosΘ(1phase)]

Where : V is Voltage, I is Current & cosΘ is Power factor

Name Plate of Induction motor| Power shown in KW|

2. Reactive Power

Reactive power is the phantom power. That floats in the system. Reactive power is being represented in VAR.

[Reactive Power= VIsinΘ(1phase)]

Where : V is Voltage, I is Current, sinΘ is reactive component

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

Name plate of transformer| — 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 floats in the circuit.

(Apparent Power)²= (Active Power)² + (Reactive Power)²

Power triangle equivalent to right angled triangle |
Right angled Triangle, A² + B² = C²
Power Triangle, Q² + P² = S²

“Power factor is the ratio of Real power to the Apparent power.”

UNDERSTANDING THE POWER FACTOR THROUGH AN EXAMPLE

Let suppose, 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 connected 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, Under which transformer works safely under the safe limits of temperature, noise & Vibration.

3 Conditions where power remains the same but difference power factor !

1. Load(Active Power) 500Watt, Power factor 1 |

P=VIcosΘ

500=110*I*1

I=500/110

I=4.54 Amps

2. Load 500Watt, Power Factor 0.8(lagging)

P=VIcosΘ

500=110*I*0.8

I=500/(110*0.8)

I=5.68 Amps

3. 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 rated 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.

Low power factor produces an excess burden on power generation utility.

CONCLUSION

Power Factor in Electrical system defines how efficiently Electrical power is being consumed.
Power Factor is the ratio of active 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/Active power is the actual useful power consumed by electrical load which is being rated as Watt.
Reactive power is the phantom power which floats in the circuit. 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.

Tagged Basics of Electricals, Power factor

Power Factor : Ultimate Guide to understand PF

POWER FACTOR