Sawtooth with offset Waveform Problem

@Chattaneer PE,  I can't seem to get the correct answer (which is letter C) using this formula. Am I using this one wrong?

BebeshKing said:

@Chattaneer PE,  I can't seem to get the correct answer (which is letter C) using this formula. Am I using this one wrong?

Click to expand...

My guess is that you were using 1/180 for δ instead of 1? δ is the duty cycle, but in the case of this waveform the duty cycle is 100%, or 1.



With

am = 0.75
Δa = 1.2-0.75 = 0.45

I get

Vrms = 0.98 

BebeshKing said:

@Chattaneer PE,  I can't seem to get the correct answer (which is letter C) using this formula. Am I using this one wrong?

View attachment 16632

View attachment 16633

Click to expand...

Observation for you:

Just by understanding Vrms you know the answer can not be A or D. It has to be somewhere between 0.75 and 1.2. So right away you got a 50/50 shot of getting it right. If you get stuck on a problem on the actual test try to eliminate answers.

Chattaneer PE said:

My guess is that you were using 1/180 for δ instead of 1? δ is the duty cycle, but in the case of this waveform the duty cycle is 100%, or 1.

View attachment 16634

With

am = 0.75
Δa = 1.2-0.75 = 0.45

I get

Vrms = 0.98 

Click to expand...

@Chattaneer PE, you're a Psychic!!. I did use 1/180 for δ instead of 1. .

Thanks for your help!

Sawtooth rms = 'AC' component = Peak/sqrt3 = 1.2/sqrt3 = 0.6928

DC rms = 0.75

Waveforms can be summed = sqrt(0.6928^2 + 0.75^2) = 1.02

if considered 'in phase' then

0.75 + 0.45 /sqrt3 = 1.0098

Attached is analytical analysis

Yepper

sqrt[(20/sqrt3)^2 + 10^2] = 15.2753

sqrt(700/3) = 15.2753