X/R Ratios 1

[maxxg]

What is the X/R ratio. If you are given the %impedance and the X/R ratio can you find the total impendance. Is the % imepedance given the reactive portion, then do you use the x/r ratio to get the real portion.

 

[waross]

The %impedance is dependant on the impedance. Use the % impedance to calculate the actual impedance. Use the quadratic equation to determine the X and R from the impedance and the ratio.

Is this a homework question?
yours

 

[mpparent]

z^2 = x^2 + r^2


Mike

 

[waross]

Hi mpparent
Did I mean the law of cosins instead of the quadratic equation. Sorry if I caused any confusion.
yours

 

[cuky2000]

i) What is the X/R ratio: This ration could provide us more than a simple mathematical quotient of the system reactance over the system resistance. X/R ratio will provide us with the characteristic of the short circuit in term of the following:
a) Rate of decay of the dc component.
b) Degree of asymmetric
c) Interrupting capability rating of protective devices.

ii) If you are given the % impedance and the X/R ratio can you find the total impedance. No. To obtain actual values of X and R, the total impedance is needed in actual values not in percent. The best that you could get is the %X and %R as follow.
X/R = tag(q) ==> q=atan(X/R)
%X = %Z.sin(q) & %R=%Z.cos(q).

iii) Is the percentage impedance given the reactive portion, then do you use the x/r ratio to get the real portion. Appears that you are confusing impedance with reactance. The following relation should be considered.
%Z = %R + j.%X _{Where: j = (-1)^1/2}
|%Z| = (%R^2+%X^2)^1/2

The between the impedance and reactance percent of impedance

 

[waross]

Thanks cuky2000
respectfully