Hello all. I have been reading a book again, things cannot go well...
I have no idea if the words I use are correct nomenclature, so if it
seems I'm over explaining my question, it's rooted in a known ignorance.
A car alternator has three phases positioned at 120 degrees to each
other. The negative "sweep" are also obviously at 120 degrees but 180 degrees out of phase. This I understand.
In the graph of this, the peaks and troughs are regularly spaced along
the time time axis. When rectified, the peaks are all positive and
seperated by 60 degrees. This I understand.
My question is: Do the stator widings have to be configured at 120 degrees?
Without changing the physical position of the stator windings, it seems
that they could be wired up so each peak, when graphed, can be at 0, 60,
and 120 degrees, with thhe troughs at 180, 240, and 300 degrees.
This graph leaves regular gaps between the groups of peaks and troughs,
but when the generated electricity is rectified, the peaks are - like
the 120 degrees-phased layout - all seperated by 60 degrees.
Is there a reason one method is used and the other isn't?
Thank you all in advance for putting up with my trivial questions!
If the phases output in a non symmetrical way the output will not
conform to 3-phase and be more akin to single phase. The efficiency
would be awful.
My explanation here is nothing like the quality found in Wikipedia and
other articles on 3-phase alternators.
On 11/05/2026 12:22, David Paste wrote:
Hello all. I have been reading a book again, things cannot go well...
I have no idea if the words I use are correct nomenclature, so if it
seems I'm over explaining my question, it's rooted in a known ignorance.
A car alternator has three phases positioned at 120 degrees to each
other. The negative "sweep" are also obviously at 120 degrees but 180
degrees out of phase. This I understand.
No. Peak voltage will be at 0 degrees where the other two phases at 120
and 240 degrees.
In the graph of this, the peaks and troughs are regularly spaced along
the time time axis. When rectified, the peaks are all positive and
seperated by 60 degrees. This I understand.
My question is: Do the stator widings have to be configured at 120
degrees?
With respect to each other, yes. In practice there are multiple pole
pairs where the polarity changes multiple times each revolution.
Without changing the physical position of the stator windings, it
seems that they could be wired up so each peak, when graphed, can be
at 0, 60, and 120 degrees, with thhe troughs at 180, 240, and 300
degrees.
They are usually connected in a star formation. That means the peak
between windings voltage is root(3) x single (star to phase)
This graph leaves regular gaps between the groups of peaks and
troughs, but when the generated electricity is rectified, the peaks
are - like the 120 degrees-phased layout - all seperated by 60 degrees.
Is there a reason one method is used and the other isn't?
Thank you all in advance for putting up with my trivial questions!
If the phases output in a non symmetrical way the output will not
conform to 3-phase and be more akin to single phase. The efficiency
would be awful.
My explanation here is nothing like the quality found in Wikipedia and
other articles on 3-phase alternators. You might also be better off referring to sketches that you can upload to photo sharing sites and
link here.
We seem to have overlooked something here ...
the purpose of an alternator in a car is to provide a DC supply, NOT a 3 phase supply - "efficient" or otherwise
also ... theres nothing limiting the number of stator windings to 3
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