Table of Contents

- What is meant by Electrical power?
- What is meant by DC power?
- What is AC power?
- Why DC power supply has a Power Factor?
- What is the Power factor?
- What are the types of power in an AC circuit?
- What is apparent power?
- What is active Power?
- What is reactive power?
- What is the difference between Active Power and Reactive Power?
- What is the difference between Active Power and Apparent Power?
- Key question Related to Power:
- 1. What is power?
- 2. What is horsepower?
- 3. What is the reason for the DC power supply is not being used in transmission?
- 4. What is Phasor?
- 5. Draw the phasor diagram for pure inductance, pure capacitance, and Resistance?

### What is meant by Electrical power?

The rate at which the work is being done in an **electrical circuit **is called an electrical power.

**Electrical power** is defined as the rate of transferred energy. Unit of power in watts. Power can be generated by a generator or **Electrical** Batteries, the consumed energy can be converted to other forms of energy like heat, motion, etc.

**Electric power is of two types**

- AC Power

2. DC Power

Electrical Power= work done by an electrical current/Time

P=Vit/t= VI=IR² =V²/R

Where, V=Voltage in volts,

I= Current in Amperes,

R= Resistance

T= Time in seconds P=power in watts

### What is meant by DC power?

DC stands for “**Direct Current”** is the one-directional flow of electric charge, Direct current may flow through semiconductors, Insulators, or Vacuum, The electric current flows in a constant direction

**Uses**

DC current is mainly used to charge the batteries, DC current is used in smelting Aluminum. It is also used in railways.

### What is AC power?

AC stands for ‘**Alternating Current**‘ which means the current alternatingly changes direction. This AC current is better for transporting current over long distances, which is why we use it for electricity transmission. For Domestic and Industrial (commercial), and is also present when audio and radio signals are carried on electrical wires

AC is used for transporting electric power through the electric grid from generators to end-users.

### Why DC power supply has a Power Factor?

In DC, the response of Capacitor and Inductor, Resistance.

**Resistance:**

The purely Resistance in DC circuit, the angle between the voltage and the current is 0˚, The power factor for a Resistance circuit is

PF=cos 0˚

Cos 0˚=1

P.F.= 1 (Unity).

**Capacitor:**

It’s the current that flows through the capacitor, C is the capacitance of the capacitor and

The voltage across capacitor is dv/dt

Current I=C *dv/dt

In DC the rate of change of voltage is zero, Current leads the voltage by 90˚

Cos 90˚=0,

So dv/dt =0,Since the DC doesn’t change its voltage so I= C *0, I=0.

The current (I)through a capacitor (C) is zero, so in DC source capacitor acts as an open circuit, therefore the open circuit doesn’t have a power factor.

**Inductor:**

Current (I) flows through an inductor circuit is DC, then voltage V across the inductor is

V=L*di/dt

di/dt=Change of current

Change of current in DC is zero, so di/dt=0, Current lags the voltage by 90˚

Cos 90˚=0

Voltage through the inductor is zero, the voltage across any component is zero which means Resistance is zero, The Inductor act as a short circuit.

So, Capacitor- open circuit & Inductor -Short Circuit Remaining Resistance-power factor is one.

So, It concludes that DC power neglects the power factor in the circuit.

### What is the Power factor?

* Power factor*is

*as the cosine of the angle between voltage and current*

**defined**Power Factor = Cosθ= kW/kVA = True power/Apparent power

### What are the types of power in an AC circuit?

- Apparent power, Denoted by the symbol (S)

2. Active power, Denoted by the symbol (P)

3. Reactive power, Denoted by the symbol (Q)

### What is apparent power?

It is the product of the RMS value of the applied voltage and current, It is known as wattless or idle power.

Apparent power S=V*I

**What is active Power?**

It is the power that is developed in the circuit resistance

It is also known as True power

P=I²R, P = E²/R

Active power, P =V*I* Cosθ.

In an AC circuit, active power is consumed by the equipment to do useful work

Defined | Symbol | Formula | Unit |

Real Power | P | P= VI cos θ | Watts |

Reactive Power | Q | Q = VI sin θ | VAR |

Apparent Power | S | S= VI | VA |

**What is reactive power?**

It is the power that developed in the circuit reactance. It is an unwanted part of the energy supplied, A minimum value of reactive power is always required to keep the voltage constant and supply useful Active power

Q=I²X, P =E²/X

Active power, P =V*I* sinθ.

### What is the difference between Active Power and Reactive Power?

Active Power | Reactive Power |

The power supply which is actually Consumed in an AC Circuit is called Active Power. | The power supply is an AC circuit that flows back and forth which means it moves in both directions (from source to load) in the circuit and reacts upon itself is called reactive power. |

Actual Power is denoted by “P” | Reactive Power is denoted by “Q” |

It is measured in units of watts | It is measured in units of Volt-Amps-Reactive (VAR) |

It works in AC and DC circuit | It works in an AC circuit |

The role of Active Power is to convert Electrical Energy into other forms of energy. | Reactive Power doesn’t convert energy, but it produces electrical or magnetic flux. |

Active power is a real power | Reactive power is a useless power |

Formulas: P=I² R, P= E²/R,P=VI Cosθ. E=Voltage I=Current R=Resistance For Single Phase (Power Supply) directly apply this formula, For Three Phase we need to add√3(1.732) | Formulas: Q=I² X, P= E²/X,Q=VI Sinθ E=Voltage I=Current X=Reactance. For Single Phase directly apply this formula, For Three Phase (Power Supply) we need to add√3(1.732). |

It is measured by a wattmeter | It is measured by a VAR meter |

In motor: Power used to cause rotation | In motor: Power used to create a magnetic field in the air gap between stator and rotor. |

Active power travels very far. | Limitation: Reactive Power doesn’t travel very far |

### What is the difference between Active Power and Apparent Power?

Apparent power is a combination of Real power and Reactive power, True power is a result of resistive components and reactive power is a result of capacitive and inductive components, these components are implemented commonly in all circuits.

Active Power | Apparent Power |

Active power is developed in resistance | Apparent power is a product of the RMS value of voltage and current |

Active power is also known as Real Power, Watt full Power, True Power, Actual Power | Apparent Power is called wattless Power or idle power |

Actual Power is denoted by “P” | Apparent power is denoted by “S” |

It is measured in units of watts | It is measured in units of Volt-Amps (VA) |

It works in AC and DC circuit | It works in an AC & DC circuit |

The role of Active Power is to convert Electrical Energy into another form of energy. | Apparent power is total power flowing |

Formulas: P=I² R, P= E²/R, P=VI Cosθ. E=Voltage I=Current R=Resistance For Single Phase (Power Supply) directly apply this formula, For Three Phase we need to add√3(1.732) | Formulas: S= E*I E=RMS Value of the Voltage I=RMS Value of the Current |

It is measured by Wattmeter | It is measured by KVA meter |

### Key question Related to Power:

**1. What is power?**

Power is the rate of the work done and its unit is joule/second or watt

It can be defined as one coulomb of electric charges moving through a potential difference of one volt in one second, the rate of work is one joule per second or one watt. hence power is obtained as a product of the voltage and current in the Electric Circuit.

P= E*I,P=I²R=E²R Where E=Voltage,I=current.

### 2. What is horsepower?

* Horsepower*(hp) is a unit of power, the work of a horse is done at a rate of time, with reference to the output of engines or motors. The horsepower was invented by James Watt. Horse power refers to the power an engine produces.

1hp=745.7watts

hp= Fd/t

hp= | horsepower |

F= | force in pounds |

d= | distance in feet |

t= | time in minutes |

### 3. What is the reason for the DC power supply is not being used in transmission?

DC is not used for transmission because DC goes heavy attenuation while transmission over long distance as we don’t transform it from low voltage.

### 4. What is Phasor?

Phasor is nothing but a vector that is rotating at a constant angular velocity. The length of the phasor or vector represents the magnitude of alternating quantity and the arrow indicates the direction of the vector.

### 5. Draw the phasor diagram for pure inductance, pure capacitance, and Resistance?

**Pure Resistance**

**Pure Capacitance**

**Pure Inductance**

## FAQs

### What are the 3 types of power in engineering? ›

These three types of power—**true, reactive, and apparent**—relate to one another in trigonometric form. We call this the power triangle: (Figure below). Power triangle relating apparent power to true power and reactive power.

**What is the relation between active reactive and apparent power? ›**

**The combination of Active Power and Reactive Power is known as Apparent Power**. It is the total power of the circuit. Mathematically Apparent power is defined as the product of root mean square (RMS) value of voltage and current irrespective of its phase angle.

**What is active and reactive power control? ›**

**Active power control is to reduce fatigue load while tracking set-points from the system.** **Reactive power is to minimize voltage deviations and optimize reactive power sharing**. •

**What is apparent power in electrical engineering? ›**

Apparent power is a measure of alternating current (AC) power that is computed by multiplying the root-mean-square (rms) current by the root-mean-square voltage.

**What are different types of power? ›**

**Types of Power in Leadership**

- Legitimate Power. Legitimate power happens when someone is in a higher position, giving them control over others. ...
- Coercive Power. There's really no time or space for coercive power in the workplace, Lipkin notes. ...
- Expert Power. ...
- Informational Power. ...
- Power of Reward. ...
- Connection Power. ...
- Referent Power.

**What is meant by active power? ›**

Active power is measured in watts (W) and is **the power consumed by electrical resistance**. True power is the current in phase with the voltage multiplied with the voltage.

**What is difference between active power and apparent power? ›**

The part of total power in an AC circuit which is consumed by the equipment to do useful work is called real power or active power. **The total amount of power flowing from source to load in an AC circuit is known as apparent power**.

**What is difference between active power and reactive power? ›**

The main difference between active and reactive power is that **Active Power is actual or real power which is used in the circuit while Reactive power bounce back and forth between load and source which is theoretically useless**. The following power triangle shows the relation between Active, Reactive and Apparent Power.

**What is the SI unit of reactive power? ›**

Reactive power, Q

IEC has adopted the name var, var (volt-ampere reactive power), for the coherent SI unit **volt-ampere** for reactive power.

**What is active power control? ›**

The active power control is **implemented by means of an adjustable speed machine, which is primarily used as a synchronous condenser, but includes a flywheel for short-term active power injection into the system**.

### What is reactive power used for? ›

Reactive power is used **to provide the voltage levels necessary for active power to do useful work**. Reactive power is essential to move active power through the transmission and distribution system to the customer.

**What is apparent power formula? ›**

Apparent power: **S = V x I (kVA)** Active power: P = V x Ia (kW) Reactive power: Q = V x Ir (kvar)

**What is the full form of kVAR? ›**

1000 Volt Amps Reactive (VAR) = 1 **kiloVolt Amps Reactive** (kVAR). Usually used to express power in all forms, but is reserved to express real power. 1000 Watts (W) = 1 kiloWatt (kW). Used to express the total load in a circuit. 1000 VA = 1 kVA (kilovolt Amps).

**What is the difference between kW and kVAR? ›**

kVA: apparent power

kVA is a measure of apparent power: it tells you the total amount of power in use in a system. **In a 100% efficient system kW = kVA**. However electrical systems are never 100% efficient and therefore not all of the systems apparent power is being used for useful work output.

**Is reactive power negative or positive? ›**

**Inductive-reactive power is conventionally positive** (absorbed by an inductive load), while capacitive-reactive power is negative (supplied by a capacitive load).

**What are 6 types of power? ›**

**The Six Types of Power for Leaders**

- Coercive Power. Coercive Power is often the least effective but most employed (and abused) type of power in the corporate world. ...
- Reward Power. Reward Power is another widely used method in business today. ...
- Legitimate Power. ...
- Referent Power. ...
- Informational Power. ...
- Expert Power.

**Why kVA rating is used in transformer? ›**

The first reason is the **power loss in the transformer**.

Thus, the total losses in a transformer depend upon volt-ampere (VA) only and not on the power factor of the load. That is why the transformer rating is given in kVA and not in kW.

**What is the importance of apparent power? ›**

The apparent power is the product of voltage and current. Apparent power is **handy for sizing of equipment or wiring**. However, adding the apparent power for two loads will not accurately give the total apparent power unless they have the same displacement between current and voltage.

**What symbol means active power? ›**

For active power P, it was decided by the Electro-technical Community to use the same unit, (watt) and symbol as the mechanical power, i.e.: **“W“**, with regards to Mr. Watt. For reactive power Q, it was decided to introduce the letter “r”.

**What does power mean in engineering? ›**

power, in science and engineering, **time rate of doing work or delivering energy**, expressible as the amount of work done W, or energy transferred, divided by the time interval t—or W/t. A given amount of work can be done by a low-powered motor in a long time or by a high-powered motor in a short time.

### What are different types of power circuits? ›

Types of Electric Circuit- **Closed circuits, open circuits, short circuits, series circuits, and parallel circuits** are the five main types of electric circuits.

**What is real power and apparent power? ›**

**Real power is the power actually consumed due to the resistive load and apparent power is the power the grid must be able to withstand**. The unit of real power is watt while apparent power unit is VA (Volt Ampere)

**How many types of power supply are there? ›**

There are **three major kinds of power supplies**: unregulated (also called brute force), linear regulated, and switching. The fourth type of power supply circuit called the ripple-regulated, is a hybrid between the “brute force” and “switching” designs, and merits a subsection to itself.

**What is control engineering? ›**

Control engineering (or control system engineering) is **the process of designing, analyzing, and optimizing a control system**. A control system is a set of devices that regulates the behavior of other devices or systems.

**What is the SI unit of power? ›**

unit of power is **watt (W)**. When a body does work at the rate of 1 joule per second, its power is 1 watt.

**What is the unit of current? ›**

The **ampere**, symbol A, is the SI unit of electric current.

**What are the 3 types of circuits? ›**

There are three basic types of circuits: **Series, Parallel, and Series-Parallel**. Individual electrical circuits normally combine one or more resistance or load devices.

**What are the 4 basic electrical circuits? ›**

The main types of electric circuits are **Close Circuit, Open Circuit, Short Circuit, Series Circuit, and Parallel Circuit**. Electric circuit provides the conductive path for the flow of electric charge or electric current.

**What are the 2 types of power supply? ›**

Two types of power supplies exist, **DC-DC and AC-DC**.

**What is the full form of kVAR? ›**

1000 Volt Amps Reactive (VAR) = 1 **kiloVolt Amps Reactive** (kVAR). Usually used to express power in all forms, but is reserved to express real power. 1000 Watts (W) = 1 kiloWatt (kW). Used to express the total load in a circuit. 1000 VA = 1 kVA (kilovolt Amps).

### What is difference between active power and apparent power? ›

The part of total power in an AC circuit which is consumed by the equipment to do useful work is called real power or active power. **The total amount of power flowing from source to load in an AC circuit is known as apparent power**.

**Is reactive power negative or positive? ›**

**Inductive-reactive power is conventionally positive** (absorbed by an inductive load), while capacitive-reactive power is negative (supplied by a capacitive load).

**What is the maximum DC voltage? ›**

The maximum voltage in DC circuit is **282 V**.

**What is DC and AC power supply? ›**

**Direct current (DC) occurs when the current flows in one constant direction**. It usually comes from batteries, solar cells, or from AC/DC converters. DC is the preferred type of power for electronic devices. Alternating current (AC) occurs when the electric current periodically inverts its direction.

**What is supply voltage? ›**

Supply Voltage/Operating Voltage Range

The absolute maximum rated supply voltage is **the maximum voltage that can be supplied between the positive supply (V _{CC}) and negative supply (V_{EE}) pins without causing characteristics degradation or damage to the internal circuit**.