Solving for coils in parallel??? COME ON!!!

Didn’t we already talk about this?

Yup, we did.  In the last video tutorial I gave you a parallel RLC circuit with pure branches.

In this one I wanted to prove my point by giving you a couple of motors (coils) in parallel.

Power is my friend right?

I’m glad you listened.  Follow these steps and you’ll be ok:

Step one:

Draw triangles under each branch.  Then draw a triangle by the source.  This is your one triangle to rule them all.


Step two:

Build power triangles for each branch.

This might mean that you have to solve a few things to achieve this.

If you are given a resistance, reactance and a phase angle (or PF) you will need to determine the branch impedance.

Once you have the branch impedance you then determine the branch current.

After the branch current is determined you can solve for the resistive and the reactive powers.  Make sure you put them in your triangles.

Power, triangles, RLC,coils

Step three:

Add up your branch power triangle into the larger triangle.

You add your watts and put them on the bottom.

Add your Vars and put them on the side.

Then through the power of Pythagoras you determine the VA.

RLC, coils, Triangle

Step 4:

Once you have your VA you can determine your I line. VA/V source = I line.

Step 5:

Using your I line you can determine your circuit impedance.  V source/ I line = impedance.

Step 6:

Use the overall power triangle to determine the circuit Power factor.

Remember that it is a ratio as Watts/VA expressed as a percentage.

power, factor

Step 7:

 Inverse Cosine the power factor and you have your phase angle.

Angle, power, factor

Step 8:

Pat yourself on the back for another job well done.  Congratulations!

Make sure you avoid the temptation to use current or impedance triangles.  Just get everything into resistive and reactive power and you’ll be ok.

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