Power Formula And Calculations (Step By Step Examples)

3 Phase Power Formula, P =√3* V * I * pf, While 1 Phase Power Formula, P = V * I * pf,

Every day, we use the power formula to calculate the power for different loads, like motors, lighting, and more.

In this article, I’ll show you step by step how to calculate power and provide a power formula below.

Table of Contents

3 phase power formula

The formula for calculating the power in a three-phase electrical circuit is:

√3

Where:

$P$ is the power in watts (W).
√3 is the square root of 3, approximately 1.732
$V_{L}$ is the line-to-line voltage in volts (V).
$I_{L}$ is the line current in amperes (A).
$cos (θ)$ is the power factor (cosine of the phase angle difference between voltage and current).

In a three-phase system, the power isn’t just the product of the line-to-line voltage (VL) and the line current (IL), as it is in a single-phase system.

To find the true power, you also need to multiply by the square root of 3 and the power factor (cos(θ)).

three phase power calculation

Let’s go through an example of a 3-phase load calculation step by step.

Example: Suppose you have a three-phase electrical system with the following parameters:

Line-to-line voltage ( $V_{L}$ ): 400 volts.
Line current ( $I_{L}$ ): 50 amperes.
Power factor ( $cos (θ)$ ): 0.9

Calculate the power ( $P$ ) in watts (W).

$P = 1.73 \times V_{L} \times I_{L} \times cos (θ)$

$\approx 69, 570 W$

ingle phase power formula

The formula for calculating single-phase power in an electrical circuit is:

Where:

is the power in watts (W).
$V$ is the voltage in volts (V).
is the current in amperes (A).
$cos (θ)$ is the power factor

This formula calculates the real power (in watts) in a single-phase circuit. The power factor () represents the phase angle difference between voltage and current and indicates how effectively electrical power is converted into useful work.

single phase power calculation example

Let’s walk through an example of calculating single-phase power step by step.

Example: Suppose you have a single-phase electrical circuit with the following parameters:

Voltage ( $V$ ): 120 volts.
Current ( $I$ ): 5 amperes.
Power factor ( $cos (θ)$ ): 0.9

Calculate the power ( $P$ ) in watts (W).

dC power formula

The formula for calculating DC (direct current) electrical power is straightforward:

$P$

Where:

$P:$ represents power in watts (W).
$V:$ is the voltage in volts (V).
is the current in amperes (A).

dC power Calculation example

Let’s walk through an example of calculating DC (direct current) power using the formula:

Example: Suppose you have a simple DC circuit with the following parameters:

Voltage ( $V$ ): 12 volts.
Current ( $I$ ): 5 amperes.

You want to calculate the power ( $P$ ) consumed by this DC circuit.

Use the DC power formula.

$P$ $= 60 W$

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