On 1 Jun 2005 12:02:57 -0700, wrote:

I have measured the DC resistance of a split-phase capacitor run
induction motor's two windings. They are 53 and 35 ohms. The motor is
impedance protected. Using the nameplate voltage and current, I have
calculated the total impedance at 60 Hz to be 110 ohms. This total
impedance is larger than the DC resistance, and so I have algebraically
subtracted the resistance from the total impedance to get the inductive
impedance, but I don't know if I did that step right:

http://users.aol.com/DGoncz/Publicat...orAnalysis.bmp

I am pretty sure about R1/R2 = X1/X2 although the winding *are*
different colors and could be different gages, but I am not sure about

1/(1/(R1+X1) + 1/(R2+X2)) = 110 ohms

I don't know if you can add a resistance and an inductive impedance
arithmetically this way. I have seen things like

R1 at angle 0 degrees + X1 at angle 90 degrees =
sqrt(R1^2 + X1^2)

I have invested hundreds of dollars into this motor/generator and while
I would like to avoid a rewind, these high resistances make a rewind
look inevitable. If I can get a good model, though, I may find a Q1
for some capacitance, and that would indicate, I think, that
self-excitation could commence.

What is not shown in MotorAnalyis.bmp is R1 in series with L1 and so
X1, and R2 in series with L2 and so X2, and R1/L1/X1 in parallel with
R2/L2/X2 and the capacitor C.


Reactance is at a right angle to resistance so it is incorrect to add
them arithmetically. This is easy to accomodate in MathCAD since it
can do arithmetic with complex variables. Just multiply your X
terms by i which MathCAD understands to be the complex operator
sqrt(-1). You can direct MathCAD to use j instead of i since j is
more commonly used in electrical engineering. Using the j
convention, an R in series with an X has impedance R + j*X. In
polar notation, this would be a Z with an angle theta. Z is the
magnitude, volts/amps and theta is the phase angle between voltage and
current.

Sample MCad sheet available if you'd like. Email me -- and tell me
which version of MCad you're running.