THD MeasurementSimple Math’s, Facts, Figures

By-EMBUILT TECHNOLOGIES

www.embuilt.comenergylogger.blogspot.com

embuilt.tech@gmail.com

Simple Math's CalculationWe all know- 1 is 1% of 100 10 is 10% of 100If two percentage are 10% and 10% then total

% is 20%

For THD Measurement1 may be 10% for 10010 may be 40% for 100

The Total of two percentage as 10% and 10% may be 0.

THD MeasurementIf Voltage (rms) is 100 Volts and first

harmonics Voltage is 99 than THD = 14.10% Means for difference of 1 Volt, THD = 14.10%If Voltage (rms) is 100 Volts and first

harmonics Voltage is 90 than THD = 43.58% Means for difference of 10Volt, THD = 43.58%

Refer Appendix -

Example for Sine Wave

We all know for pure sine wave THD is 0%

If we connect a ideal load with ideal half wave rectifier for positive half. Let the THD of this wave is 37%

If we connect a ideal load with ideal half wave rectifier for Negative half. The THD of this wave is also 37%

If we add both Rectified waves

THD will be zero where as individual wave has THD 37% .

AppendixVrms2 = (V12+V22+V32+…..+Vn2)

THD(%) = (√(V22+V32+…..+Vn2 )/ √(V12+V22+V32+…..+Vn2)

THD(%)= (√(Vrms2-V12)/ Vrms )*100

THD ( dB) or Distortion attenuation a =20*log((THD%)/100)

THD Calculation Sheet