Calculating Impedances in Polar Coordinates: Tips and Tricks

[barry-]

Hello all i have a question about adding 3 impedances given in polar form, must i convert them to x..y.. first or is there a quicker way on a calculator and if so can anyone give advice i have the equation Zo=√Z(oc)Z(sc) but finding it hard to understand many thanks.

 

[gnurf]

i have a question about adding 3 impedances given in polar form, must i convert them to x..y.. first or is there a quicker way on a calculator and if so can anyone give advice i have the equation Zo=√Z(oc)Z(sc)

Are you sure you didn't mean multiplying two impedances? In that case, if Z_oc and Z_sc are two complex impedances in polar form, their product is a new complex number with magnitude |Z_oc|× |Z_sc| and phase angel φ_oc + φ_sc.

[...]finding it hard to understand many thanks.

It's easier to understand many thanks if you use punctuation.

 

[barry-]

well its 3 impedance in series and parallel so if i use the formula z =z1z2/z1 + z2 and am i right that in polar form you multiply the x-axis and add the y (i.e the value given as the angle)? that will sort the 2 impedances out in parallel then the remaining impedance will be in series with that and i can just add them, Thank you

 

[jim hardy]

Congratulations on improved punctuation !

Yes - you can add in rectangular,

and you can multiply in polar as you described. I'd have said " Multiply the magnitudes and add the angles" , though. To say X and Y implies rectangular.

I learned this in slide rule days so it's ingrained.
I really suggest you work about ten examples on paper so it'll become habit for you.

I was through college before pocket calculators appeared. When the HP35 came out ~1972 with its one button polar-rectangular conversion the EE world was flabbergasted.

So there's probably an easy way to do it with a modern calculator. But you should become fluent in the method so you can spot errors coming from missed keystrokes.

My two cents !

old jim

 

[barry-]

:) thanks english is not a strong point of mine, thank you for the help, I am sure my calculater can add them but I am not sure how, so as long as it can convert between polar and rectangular and then do what i need to do il be happy, thank you.