Skewed stator

[Ian]

I have a couple of 7.5 KVA ST alternators. Having taken both of them apart I have been struck by just how similar they are in materials and construction despite them coming from different suppliers and with different brand names. Both of my ST alternators have skewed stators which surprised me; I was not expecting this.

Having followed this forum for about a year, and noting comments about poor waveform output, I was expecting a linear stator. I do not have a scope so I cannot see what the output waveform is like but I have had no trouble with any equipment so far and the skewed stator would lead me to believe that the waveform should be pretty good.

So …
1.   Are ALL ST alternators like this ?
2.   Has anyone put a scope on a skewed stator ST head and evaluated the output waveform ?

Regards,
Ian

[Doug]

Yes people here have scoped the stators and most of the hramonic probl;ems seem to be related to the harmonic winding.

Its easier to skew a rotor lamination than pole so this is why they do it. Induction motors generaly have cast rotor bars so its easier to cast the skew than spin and nest wires in skewn stator laminations but this isn't always the case.
Asea used to make a haring bone sort of patern in the rotors of some of there motors to do the same thing ( reduce cog and cusp ), but this comes back again to the inmates inthe artic again....

[Ian]

Thanks Doug.

Looking at my generators and your comments, am I right in thinking that the rotor bobbins will have been wound on a machine or jig of some kind (it certainly looks like it with a good even and well tensioned winding), whilst the stator coils (output winding, harmonic winding, and stupid 6v tell-tale light bulb windings) are done by hand ?

I can understand the use of fabric / ceramic insulation within the slots around the wire runs, but what are the sheet (paper) like materials on the coil radii at each end of the stator for ? They look like they have been applied by hand also and then the coil radii tied off with some fabric yarn of some kind.

Regards,
Ian

[Doug]

All the winings are done on a coil making machine....

The difference you probably are seeing is probably caused by a slightly sloopy fit of the stator coils.
Mine is no better.
If you make the coils to small its hard to lay them in place, too large and the ends are sloppy and hard to neatly lace.

Also how you lace them and the time you tale to shape coils makes a huge difference in how it looks.

Functionaly I wouldn;t worry about it.