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The known value of THD for a pure rectangular switching function, for which the duty ratio D = 0.5, is 0.483 or 48.3%. I have tried to back-calculate this using formulae for THD in order to work out the THD for a switching function assuming the dc component has been removed by filtering.

Considering the RMS value is

enter image description here

I got the following:

enter image description here

Upon plugging the duty ratio value of 0.5 into D, my result is 40.507, whereas it should come out to 0.483. I'm positive that I'm not plugging it into the calculator wrong, and that the equations are correct. Why is it not coming out to 0.483?

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  • \$\begingroup\$ Please show your solution \$\endgroup\$
    – Voltage Spike
    Commented May 23 at 16:54

1 Answer 1

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It does come out to 0.483426 for D=0.5. You forgot to switch the calculator from DEG to RAD.

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  • \$\begingroup\$ You're absolutely right, I did forget. I ought to be drawn and quartered for this! \$\endgroup\$ Commented May 23 at 11:17

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