Total voltage of 3 AC voltages

I have the following problem and I'm not sure if I did it correct:

Given v(t) =10 + 5 Sin (377t+30 degrees) - 7 Sin (377t-45 degrees)

Find VRMS

Putting them into rectangular form:

(7.07 + j 0) + (3.06 + j 1.77) - (3.5 - j 3.5)

now I add my reals and imaginaries and that's my answer? Or I can convert that number into polar as well.

Reply to
Peter
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sounds like homework to me sonny..

sQuick..

Reply to
sQuick

and? I'm asking a question so I can understand it better. I've done half the problem already!

Reply to
Peter

You have also gotten the wrong results for that half. You may understand the concept of polar to rectangular conversion, but your trigonometry math is wrong. It helps to draw your vector, then the real and imaginary sides of the triangle and do the math from there. Show all work. You have another mistake but I'm not going to tell you what it is.

Back in high school trig (college prep track 1978-79), Mrs. Fliegel made us memorize sine, cosine and tangent at 0, 30, 45, 60 and 90 degrees. We also had to draw them freehand on trig graph paper. Calculators were not allowed in that class!

Mike

Reply to
Mike Lamond

The first term looks like a dc term.

Bill

-- Ferme le Bush

Reply to
Salmon Egg

You cannot use phasor since you have a DC component.

Recall that RMS = root-mean-square.

Therefore, to obtain Vrms first calculate the square of v(t), i.e. [ v(t) ]^2. Then integrate the result over one cycle, i.e., from t=0 to t=1/(60), and then divide the result by 1/(60) to obtain the mean. Take the square-root of the result. The answer is the Vrms.

Reply to
Figaro

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