# AC LR-C parallel circuit

Discussion in 'Homework Help' started by monkeyhead, Feb 29, 2008.

Mar 5, 2007
45
0
Hi there!
Basically I'm ploughing through my assignment and trying to work out the phase angles of a capacitor, of the coil and of the supply.

I was given the values as follows:

Supply: 260V @ 50Hz
Inductor: 31.831mH
Resistor: 24 Ohm

I had to work out the value of the cap which I worked out as: 47.1 uF

My attempt
Note: Results given rounded to 2dp.

I worked out that the current through the coil and its phase angle as follows:
Current: 10A
Angle: 23º

( I did this by working out Xl, then the impedance then using ohms law and results were similar from simulation)

I also worked out the current in the cap and its phase angle as follows:
Current: 3.85A

( I did this by working out Xc, then using ohms law and results were similar from simulation)

Now for the supply angle and its current I did the following.

I worked out the the total horizontal component which was = 9.21A

Then did the same for the vertical components and that calculated at = -0.06

Then calculated I by doing the following I= √((9.21)²+(-0.06)²)= 9.21

To get the angle I used inverse tan as follows:
tan-1(0.06/9.21)=0.37º

To me this angle seems way to small?! Have I gone wrong somewhere?

Many thanks,