In the highlighted portion for the AVERAGE power, why did he use the DC RMS output voltage and not the DC AVERAGE output voltage?
Do we ever use the DC AVERAGE output voltage for finding power?
SOURCE:
Power Electronics
Daniel W. Hart
published by: Pearson Education, Inc., 2010
ISBN 978-0-07-338067-4
RMS is used because it yields the correct answer. Power (including instantaneous power) is proportional to the square of voltage, not to the voltage.
Where RMS and average differ, using average will give the incorrect answer for power.
Intuitively, the “spikier” the voltage waveform is, the greater the difference will be.
For example, consider a 1 ohm resistor and a voltage source that spikes to 100V with 1% duty cycle. The average voltage is 1V. RMS voltage is 10V.
The power is 10kW for 1% of the time or 0W for 99% of the time, averaging out to 100W, not 1W (as it would be for 1VDC).
