Author Topic: True RMS and Duty cycle calculation  (Read 563 times)

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Offline rrn

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  • Country: us
True RMS and Duty cycle calculation
« on: December 03, 2021, 04:03:35 am »
Can someone help with calculating modified sine wave true RMS value and also how to Control PWM dutycycle to maintain fixed output.
Example: input volatge 100Vdc.
Need to maintain fixed Vrms 50VAC
Frequency = 50hz
Modified sine wave same as in the picture
 

Offline gcewing

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Re: True RMS and Duty cycle calculation
« Reply #1 on: December 03, 2021, 07:22:00 am »
For PWM with duty cycle d,

Vrms = sqrt(d * Vin**2) = sqrt(d) * Vin

so

sqrt(d) = Vrms / Vin

or

d = (Vrms / Vin) ** 2

So for Vin = 100V and Vrms = 50V, you want d = 1/4.

The frequency doesn't come into it.
 


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