# Average and rms value in a diode or thyristor/scr - Please help!



## poosri (Apr 13, 2015)

When do you use (2*Vpeak)/3.14 and when do you use just (Vpeak/3.14)

This is just so confusing esp. when going thru' these problems in CI tests....I am very nervous about the power electronics type problems in the exam :wacko:

does anyone have set of formulas on this? (average, rms values etc on power electronics, batteries) - Please share.Thanks a lot!


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## Panchito (Apr 13, 2015)

If you have a FULL-WAVE rectified sine wave, the average value is 2*Vpeak/pi, and the RMS value is Vpeak/SQRT(2)

If you have a HALF-WAVE rectified sine wave, the average value is Vpeak/pi, and the RMS value is Vpeak/2


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## Kovz (Apr 14, 2015)

Download the free NCEES Reference manual for the FE exam. It has all those equations for half-wave and full wave rectified sine waves.


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## MyBeardAndMe (Apr 14, 2015)

Kovz, does it have anything that the table in Camara doesn't already have?


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## Kovz (Apr 14, 2015)

MyBeardAndMe said:


> Kovz, does it have anything that the table in Camara doesn't already have?




Which table are you referring to? Table 27-2 on Page 27-6?


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## MyBeardAndMe (Apr 14, 2015)

Can't remember which one it is off the top of my head. In Camara, I think the table shows the circuit, what the waveform looks like, and then equations for Vrms, Vavg, and Vpk.


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## Kovz (Apr 15, 2015)

MyBeardAndMe said:


> Can't remember which one it is off the top of my head. In Camara, I think the table shows the circuit, what the waveform looks like, and then equations for Vrms, Vavg, and Vpk.




Yeah that table is actually better than the FE Reference. I wasn't aware of it until you pointed it out. Thanks for sharing.


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