# Getting Started with Simulink: Simple Power calculations

**Getting Started with Simulink: Simple Power calculations**In this small example, we will calculate the instantaneous power along with average rms power and voltage using simulink when equation of V and I are given.

**Problem:**

if v(t)=10cos(120πt+30) and i(t)=6cos(120πt+60).Determine the average power and rms value of v(t).

**Formulas Used:**

As we know instantaneous power is given as

\[P(t)=v(t) i(t) \]

and average power is given as

\[P_{avg}=\frac{1}{T} \int_0^T{P(t)dt} \]

similarly rms voltage is given as

\[V_{rms}=\sqrt {\frac{1}{T} \int_0^T{V^2(t)dt}} \]

where T is an integer multiple of timeperiod.

**Source Creation:**

First we will create two sin sources V and I and adjust their parameter to match the problem

V Source:

Amplitude: 10

freq: 60

phase: pi/6

sample time: 0.01

I Source:

Amplitude: 6

freq: 60

phase: pi/3

sample time: 0.01

**RMS Voltage**

we will simple follow the equation of Vrms for the calculation.

1. first put a math function block, double click on it and change the equation as u^2

connect this block's input from the output of V source.

Output of this block represent V^2

2. Now put a integrator block and connect the input of it from V^2. The output represents \[ \int_0^T{V^2(t)dt} \]

3. Now put a divider block and connect the output of integrator to its input.

Output of this block represents \[\frac{1}{T} \int_0^T{V^2(t)dt} \]

4. Put a math function block, double click on it and change the equation as sqrt. Now connect this to

the output of step3.

5. Put a display block and connect the step4 output to it.

Fig1: Simulink model for RMS Voltage calculation |

**Instantaneous Power**

Calculation of Inst, Power is very simple. Just multiply the V and I source and put a scope block to display it.

Fig2: Inst. Power |

**Average Power**

Again Average Power calculation is simple and follows from RMS Voltage calculation. Put an integrator and divide block after the instant. power and connect it with the display block.

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