Computing voltage and current amplitude and average power

Hello,

I have three sinusoidal waveforms namely, voltage, current, and power acquired using an oscilloscope which I then have connected to my computer that runs Matlab. I need to compute the voltage and current amplitudes and the average power using the following formulae.

1. Voltage Amplitude =
2. Current Amplitude =
3. Average Power =

where, represent the period, instantaneous current and voltage respectively. How do I use the waveforms obtained via the oscilloscope to find the above amplitudes and power?

[Image Analyst]

Attach your arrays for those variables in a .mat file. You said you have them, so let us have them too.

Make it easy for us to help you.

[hosein Javan]

Star Strider x_max = sqrt(2)*x_rms .

[Sudarshan]

@Image Analyst.

Please find the arrays for the current, voltage and power in the attached .mat file.

[hosein Javan]

if you're using simulink, you don't have to export then analyze them. use the tools that I mentioned in the answer and you should be fine.

Answer 1

[hosein Javan]

if they are 3-phase, use clarke transformation. it will give you the amplitude and phase the dividing by sqrt(2) yield the rms value. multiplying V_rms*I_rms = P_average.

if they are single phase. and you know the instantaneous frequency, use sliding average "movmean" function to calculate it. there are simulink blocks available for such task.

if they are single phase and you don't know the instantaneous frequency, then you have to use "PLL" to measure phase or frequency to calculate rms values.

[Sudarshan]

Hosein Jevan,

I am measuring the voltage across and current through a capacitor and trying to calculate the average power. This average power along with current and voltage amplitude is required to determine the ESR and capacitance of the capacitor. Plese find the attached circuit for your reference.

The IEEE paper I am referring is "Estimating aluminum electrolytic capacitors condition using a low frequency transformer together with a DC power supply".

[hosein Javan]

I've imported your data to simulink, as I said, the blocks work. notice that due to your supply of 50 Hz, we didn't have to measure frequency. only give the rms block fundamental frequency of 50 Hz. the average power is too small due to capacitor's power factor. please don't forget to hit "Accept".

[Sudarshan]

Thank you hosein Javan.

[hosein Javan]

you're welcome.