This post is specially designed to understand the term “Power Triangle”. First, we must review some important Electrical Terms. These include Electrical power, Types of Electrical power, and Frequency in Electrical systems. We should also understand Power factor, Types of AC power, and types of electrical loads.
Electrical Power
Electrical power is flow of electrical energy with respect to time. ‘Wattage‘ is the unit of power Which is represented as ‘Watt‘.
- P=E/t (P=power, E=energy, t=time)
- P=Eq/tq (q=charge)
- P=VI (E/q= Voltage, q/t=current) Electrical power is product of voltage & current.
Types of Electrical Power
There is two types of Electrical powers; AC & DC.
AC stands for ‘alternating current’ While DC stands for ‘direct current’.
AC , as its name describes, Its voltage and current components continuously changes the magnitude with respect to time in an alternate manner.
DC, Voltage & current components of DC remains fixed though out the time. It does not change its direction. Both the power types are explained through a GIF below :
In a GIF below AC sinusoidal waveform is shown. An electrical load is connected across an AC supply through a switch. When switch get connected. Both voltage & current starts flowing in sinusoidal waveform. Both waves originates from origin zero. First, Both the waves moves in positive half than it moves in a negative half.
In a GIF below, DC waveform is shown. An electrical load is connected across a battery through a switch. When switch get closed, Voltage get appear across the load & current starts flowing. Both current & voltage moves in a stable form at fixed maximum magnitude.
Frequency in AC system
Since AC , continuously changes its direction in an alternate manner. A term get exist in AC & that is ‘Frequency‘.
Frequency represents the number of cycles with respect to time. AC waveform moves from positive to negative & negative to positive. That’s why frequency term existed in AC .
AC GIF shown above in which AC waveform with 1 positive & 1 negative half is been shown. Both the halves in combine represents 1 cycle. In AC , Frequency is number of cycles per second. ‘Hz‘ is the unit of frequency. 1 Hz represents 1 cycle per second & 60 Hz represents 60 cycles per second.
Power factor in AC system
DC, Its components like voltage & current remains stable at their magnitude. But components of AC moves with respect to time in an alternate manner. Due to load type, An angle get formed in between voltage and current. That angular component is known as the power factor (cosΘ).
Angular component produces an huge impact on electrical power & AC power becomes; P=V*I*cosΘ
In AC power GIF shown above, Voltage & current both the components moves together at an angle of 0°. At 0° power factor; Cos 0° becomes 1. Power get again equal to the product of voltage & current(V*I*1=V*I).
But what will happen when an angle get created in between voltage & current.
A GIF of AC waveform is shown next. In which a cosine angle get existed in between voltage & current. An electrical load is connected to AC supply through a switch. When switch get closed voltage get appear across motor & current starts flowing.
This time due to an angle voltage & current waves are not parallel. In between both the components angular time lag get existed.
Let suppose, An Electrical load having a rating 1 kW & Voltage is 230 V AC.
Next, Current is calculated at different power factor ratings.
P=V*I*cosΘ
- At power factor 0.9, I=1000/(230*0.9)=4.83 Amps
- At power factor 0.8, I=1000/(230*0.8)= 5.43 Amps
- At power factor 0.7, I= 1000/(230*0.7)=6.21 Amps
It is clearly seen as power factor decreases, Current in line increases. For same 1 kW, different level of line current flows; All due to power factor . That’s why power factor is very important to consider in an AC powered circuit.
Types of AC power
Till, We have seen 2 Electrical power formulas; that are
The term power factor varies from 0 to 1. At power factor 1, maximum power delivered which is equal to the product of voltage & current.
At 0 power factor, power delivery becomes zero. We can say power P1 always stay higher or equal to P2. But P2 power can never go higher than P1.
- The power P1 is known as ‘Apparent power‘.
- While P2 is known as ‘True power‘ or ‘real power‘.
- When P1 is higher than P2, a difference get exist & that term is known as ‘Reactive power‘ P3.
Types of Electrical loads
Basically, There are three types of electrical loads & that are ;
Resistor
A resistor has a property; it resists the flow of electrical current. This property is known as ‘Resistance(R)‘.
Most of the power across the resistor is utilized or wasted in a heat generation. There is very less or minor impact of power factor in case of resistor. Power factor remains stable at around 1 in case of resistor Which results power becomes; P=V*I
Reactive power in resistive circuit remains near around zero. Which results Apparent power & true power get equal.
Inductor
Inductor is a type of coil of insulated wire. Inductor stores the energy in a form of magnetic field. When electrical power is applied to an Inductor, it creates a type of resistance. That resistance is known as ‘Inductive reactance (XL)’. Current lags behind the voltage in Inductor that’s why power factor falls below 1.
Reactive power across inductive circuit increases While true power decreases.
Capacitor
Capacitor appears like a sandwich, In which dielectric material is sandwich in between two conductors.
Capacitor stores the energy in a form of electrostatic charge. When electrical power is applied across Capacitor, It also induces a type of resistance which is known as ‘Capacitive reactance(XC)‘.
Current leads the voltage in Capacitor & power factor also fall below 1 but in a leading side.
Reactive power across capacitive increases While true power decreases.
A power factor graph is shown below. This graph shows the unity power factor at the center. The lagging and leading power factor are displayed on either side of the unity power factor.
In resistive loads, Power factor stays near around 1. In inductive loads, Power factor lags behind 1. In capacitive loads, Power factor lead behind 1. This is like a balancing the scale in which both the loads; Inductive & Capacitive loads are counter to each other.
This leading or lagging power factor raises the power which is know as ‘Reactive power’.
Power Triangle
All the three AC power types, ‘Apparent power’, ‘True power’ and ‘Reactive power’ can easily be arranged in a right angle triangle. That triangle is known as “Power triangle“.
True power act as a Base line of triangle.
Reactive power act as a perpendicular of triangle.
While Apparent power act as a hypotenuse.
True Power (KW)
Base of triangle represents the ‘Real power’ also known as ‘true power’. Real power is truly useful power which is utilized to deliver the required output. Such that heat energy originating from heating coil running from an AC supply. True power is product of voltage, current & cosine angle in between voltage & current , Such that P=V*I*cosΘ
Reactive Power (KVAR)
Perpendicular of triangle represents the Reactive power. Reactive power is imaginary power which float on the circuit. This power helps to generate magnetic field in Electrical machines such as Transformers & Alternators . Reactive power is product multiple of Voltage, Current & sine angle in between voltage & current, Such that P=V*I*sinΘ
Apparent Power (KVA)
Hypotenuse of triangle represents the apparent power. It is the total sum of real power & reactive power. Power generating electric utilities charge on this power. That’s why power consumer tries to minimize the reactive power by increasing the power factor. This power is product multiple of voltage & current, Such that P=V*I
SUMMARY
- Electrical power is flow of electrical energy with respect to time. ‘Wattage‘ is the unit of power Which is represented as ‘Watt‘.
- P=VI (E/q= Voltage, q/t=current) Electrical power is product of voltage & current.
- There is two types of Electrical power; AC & DC. AC stands for ‘alternating current’ While DC stands for ‘direct current’.
- Since AC, continuously changes its direction in alternate manner. A term get exist in AC & that is ‘frequency‘.
- Frequency means number of cycles with respect to time. AC waveform moves from positive to negative & negative to positive.
- Due to load type, An angle get formed in ac power in between voltage and current. That angular component is known as the power factor (cosΘ).
- Three basic electrical loads are Resistor, Inductor & Capacitor.
- All the three AC power types can form a right angle triangle. These types are ‘Apparent power’, ‘True power’, and ‘Reactive power’. That triangle is known as “Power triangle“.