Problem Set 1: Difference between revisions

Revision as of 22:58, 8 February 2010

Problem

Find the core inductance and resitence of a transformer using measurmnets Voc=5V, Ioc=3A, and Poc =10W.

Solution

Power is found only through resister

$Poc=Voc^{2}/R\!$

Both Poc and Voc are giving so solve for R

$R=Voc^{2}/Poc=5V/10W=2.5Ohms\!$

To calclate the core inductance we will use the formular for apparent power.

$S^{2}=P^{2}+Q^{2}\!$

$S^{2}=|Voc*Ioc^{*}|^{2}\!$

Subtituting in values and solving gives

$S^{2}=(5V*3A)^{2}=225(VA)^{2}\!$

Use the apparent power and the real power to find the reactive power

$Q={\sqrt {S^{2}-P^{2}}}={\sqrt {225^{2}-10^{2}}}=224.8VAr\!$

Reactive power is stored in non-linear impedence represented as X. In this case X is inductance.

$Q=Voc^{2}/X\!$

$X=Voc^{2}/Q=5V^{2}/224.8VAr=0.11H\!$

@@ Line 8: / Line 8: @@
 '''Solution'''
-\!
 Power is found only through resister
@@ Line 31: / Line 31: @@
 <math>Q=\sqrt{S^{2}-P^{2}}= \sqrt{225^{2}-10^{2}}= 224.8VAr\!</math>
+Reactive power is stored in non-linear impedence represented as X. In this case X is inductance.
-Finally
-<math>Q=Voc^{2}/X\!</math>
-Solve for the inductance
 <math>Q=Voc^{2}/X\!</math>