Motor problems

[Super God]

Argh, this has been plaguing me for so long, and I don't know what's up.  Maybe someone with some motor experience could help?  Everytime I wind a coil or two for a motor and connect it to the AC transformer I have, it shorts out!  I have a magnet in the middle acting as a rotor and 4 stator coils on the outside.  Maybe I'm not using enough windings?  It's about 50 for each.  This is really bugging me.  =[  Can someone please lend their expertise?

[gyulasun]

Hi,

I do not have much motor experience but have AC transformer experience. From your description, your 50 turns of wire on the stators sounds way too small, hence there is no sufficient AC impedance at your 50 or 60Hz AC frequency you feed in from your transformer.  Of course here I assume you do not have shorts between the turns etc.

The best would be to measure one stator coil self inductance with a meter [maybe you (or friends near you) have a digital multimeter with inductance measuring range]. 
Once you have info on your stator coil inductance you may estimate its AC impedance
(XL=2pi*f*L) and from this the AC current may be estimated too (Vac/XL), I have neglected the obviously very small DC resistance of your 50 turns.  Vac is your transformer secondary output voltage.
An example: let's say you could measure 10mH self inductance for one stator coil. (This 10mH may be practical for a higher permeability core with 50 turns.)
The inductive reactance for 60Hz AC is about  2pi*60*0.01=3.77 Ohms and for 50Hz it is about 3.14 Ohms. And if your transformer has a 12V AC secondary to feed the stator coils, the load such one coil places on it can be 12/3.77=3.18A and if you connect the 4 coils in series this current then reduces to 3.18/4=0.79A, if you connect the coils in parallel this current need increases to 3.18*4=12.73A. 

And if I erred in estimating your stator coil inductance and it is in fact only 1mH of value due to a smaller permeabilty core you happen to have, then the current need for one stator coil at the 12V AC secondary gets multiplied by a factor of 10 i.e. to 31.8A due to the much lower inductive impedance (0.377 Ohms), now this is a real short circuit for your transformer secondary, even if you connect all the 4 stator coils in series.

Regards
Gyula

PS: I am aware of the real calculations needed in AC circuits when resistors and inductances are in series etc, but here I deliberately used a simplification due to the very small DC resistance the 50 turns of wire represents.

[Super God]

Thank you very much.  All of my multimeters have been 'borrowed', hopefully I'll get a nice benchtop one soon.  I don't have much motor experience, my little 40 watt transformer goes crazy whenever I plug it in.  I was thinking about 200 turns for each stator for a sum of 800 turns in total.  I'll try that and if that doesn't work, I'll do 1000 turns for each stator.  That huge spool of 34AWG transformer wire I bought seems to be endless

Thank you so much for your time!

-Brian