Table of Contents

**What is Power?**

Power is defined as the work done per unit time. The SI unit of power is Watt (W) which is equal to joules per second (Joule/second).

**Power = Work / time**

**P = W / t**

**Electrical power is** generally defined as the rate at which electrical energy is consumed in electrical circuits. The SI unit of power is the watt, which is equal to one joule per second. In an electrical system, the power (P) is equal to the voltage(volt) multiplied by the current (Amp).

**Ampere**–

An ampere is the unit of electrical current. Ampere is defined as how many electrons pass a certain point per second. That is equal to one coulomb of charge per second, or 6.24 x 10^18 electrons**/**second.

**Volt** –

It is the basic unit of electromotive force in the SI and MKS systems, equal to the electromotive force, or difference in potential, that causes a current of one ampere to flow through a conductor having a resistance of 1ohm.

**Watt** –

Watt is the basic unit of electric, mechanical, or thermal power in the SI and MKS systems, It is equal to one joule per second or 10 ergs per second (of a horsepower).

**In case electrical systems power is equal to one volt-ampere.**

## Method of converting Watts to Amps or Amps to Watts

If you have at least two of the following:** amps, volts or watts** then the missing one can be calculated easily. Since watts are amps multiplied by volts, there is a simple relationship that exists between them.

**Current (Amps) =Power(Watts)/Voltage(Volt)**

Example 1: Imagine that you have an air conditioner rated for 600 watts on a fixed 120V circuit. How many amps is it?

Amps = 600 ÷ 120 = 5

So the air conditioner is rated for 5 amps.

__Formula to convert amps to watts__

__Formula to convert amps to watts__

To convert electric current in amps (A) to electric power in watts (W) simple formulas are used as follows –

**ConvertintDC amps to watts**

The power P in watts (W) is calculated as the current in amps (A), multiplied by the voltage V in volts (V):

**P**_{(W)}** = I _{(A)} × V_{(V)}**

**Or**

**watt = amp × volt**

**Ex: **What is the power consumed in watts when the current of 4A is given and the voltage supply is 110V?

**Sol: **The power P is equal to current of 4 amps times the voltage of 110 volts.

P = 4A × 110V = 440W

**Single Phase AC amps to watts conversion:**

The real power is calculated as –

**P**_{(W)}** = PF × I _{(A)} × V_{(V)}**

**Or Watt = PF × amp (A)× volt(V)**

Here ;P= real power P in watts

I=Phase Current in amps

V= RMS voltage V in volts (V)

**Example: **Find out the power consumption in watts when the power factor is 0.6 and the phase current is3A and the RMS voltage is 110V?

Answer: The power is directly calculate by using

P = PFX amps X volts

P = 0.6 × 3A × 110V = 198W

**Three phase AC amps to watts calculation formula**

__In case of line to line voltage:__

The real power P in watts (W) is calculated using simple formula

**P _{(W)} = √3 × PF × I_{(A)} × V_{L-L(V)}**

**or**

**W = √3 × PF×A × V**

PF= power factor

I=phase current in amps (A)

V= line to line RMS voltage *V*_{L-L} in volts (V):

**Example: **Calculate the power consumption in watts when the power factor is given as 0.6 and the phase current is 4A and the RMS voltage supply is 110V?

Answer: Power P, is calculated as a power factor of 0.6 times current multiplied by volts

P = *√*3 × 0.6 × 4A × 110V = 457.26W

** In case of the **line to neutral voltage:

**The real power P in watts (W) is calculated by using the simple formula**

__At balanced load condition__:**P**_{(W)}** = 3 × PF × I _{(A)} × V_{L-0(V)}**

**or W = 3 × PF×A × V**

Here V= line to neutral RMS voltage *V*_{L-0} in volts (V).

__Method of converting watts to amps__

__Method of converting watts to amps__

To convert electric power in watts (W) to electric current in amps (A). Here discussed the simple formula

__Watts to amps calculation formula:__

The current I in amps (A) is equal to the power P in watts (W), divided by the voltage V in volts (V).

**I**_{(A)}** = P _{(W)} / V_{(V)}**

**Or A = W / V**

**Example**

What is the current in amps when the power consumption is 400 watts and the voltage supply is 100 volts?

I = 400W / 100V = 4Amp

**Calculate single phase watts to amps :**

The phase current I in amps (A) is calculated by using a simple formula, real power P in watts (W), divide by the power factor PF times the RMS voltage in volts (V):

**I**_{(A)}** = P _{(W)} / (PF × V_{(V)} )**

So amps are equal to watts divided by power factor times volts.

or

**A = W / (PF × V)**

**Example:**

Find the phase current in amps when the power consumption is 330 watts, the power factor is 0.6 and the RMS voltage supply is 220 volts?

I = 330W / (0.8 × 110V) = 2.5Amp

**AC three phase watts to amps :**

__Amps calculation with line to line voltage__

Phase current I, in amps (A) is calculated by dividing the real power P in watts (W), to the square root of 3 times the power factor PF, and line to line RMS voltage VL-L in volts (V). The formula is given below:

**I**_{(A)}** = P _{(W)} / (√3 × PF × V_{L-L(V)} )**

or

**A = W / (√3 × PF × V)**

**Example**

Calculate the phase current in amps when the power consumption is 330 watts, the power factor is 0.6and the RMS voltage supply is 220 volts?

I = 330W / (*√*3 × 0.6 × 220V) = 1.44Amp

__Calculate amps with a line to neutral voltage__: At balanced load condition

The phase current I in amps (A) is calculated a**s**

**I _{(A)} = P_{(W)} / (3 × PF × V_{L-0(V)} )**

amps are equal to watts divided by 3 times power factor times line to neutral volts

**A = W / (3 × PF × V).**

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