17.02.2013 Views

ExtraClassSylalbus2009jan-AD7FO

ExtraClassSylalbus2009jan-AD7FO

ExtraClassSylalbus2009jan-AD7FO

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

Rev 2.02<br />

Parallel circuit solutions<br />

Solving for parallel circuits for ac circuits is similar to the way we solved resistance parallel circuits. Remember the<br />

Equation:<br />

The solution involved finding the conductance (G) of each leg by dividing the resistances into 1 and summing them.<br />

This gave the total circuit conductance in Siemens. The Mho was the term previously used for Seimen.<br />

To find the resistance we divided the conductance into 1 and ended up with the parallel circuit resistance.<br />

We do the same thing to find the impedance of parallel ac circuits. The names of the circuit references change-<br />

Impedance becomes admittance, “Y”, (1/impedance). Resistance becomes conductance, “G”, (1/resistance)<br />

and susceptance , “B” (1/reactance) We start by finding the “conductance of the resistive and reactive<br />

components and just add them as we did in the resistance solution (remember we will be summing resistive (real)<br />

and reactive (imaginary) conductance. The rectangular coordinates for parallel circuit solutions are shown below.<br />

Note that the reactive axis direction is opposite that of the series circuit solutions in that that reactive conductance<br />

is + for capacity and – for inductance.<br />

E5C16<br />

In polar coordinates, the impedance of a circuit that has an admittance of 7.09 milli-siemens at 45 degrees is 141<br />

ohms at an angle of -45 degrees.<br />

Polar Impedance (Z) =1/admittance or Z= 1/.00709 or Z= 141.04Ω<br />

Polar angle = 1 / j (admittance angle) = 1/j(45°) or -j45°<br />

E5C17 (C)<br />

In rectangular coordinates, the impedance of a circuit that has an admittance of 5 millisiemens at -30 degrees is C.<br />

173 + j100 ohms.<br />

Polar Impedance (Z) =1/admittance or Z= 1/.005 or Z= 200Ω<br />

Polar angle = 1/amdittance angle = 1/- 30° or +30°<br />

Cos θ= resistance(R) / Impedance(Z) or R = 200Ω x Cosine 30° or R = 200Ω x .866 or 173.2 Ω<br />

Sin θ= reactance(j) / Impedance(Z) or j = 200 x Sine 30° or j = 200Ω x .50 or j100Ω<br />

Jack Tiley <strong>AD7FO</strong> Page 47 3/15/2009<br />

Susceptance

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!