Stepped Sepex

[David Dymaxion <david_dymaxion@yahoo.com>]

I was thinking about Rich's and John's twin motor setups. A thought I
had was maybe it would be better to just switch the fields from
series to parallel, and leave the armatures in parallel all the time.
Hence my title, "stepped sepex." In series you get twice the field
current as armature current; in parallel you get the same current in
the field and the armature -- so it is like sepex with only two
steps.

Now I'm sure Lee will politely offer a sound argument as to why this
would make no difference compared to switching the whole motors from
series to parallel. As long as I'm blissful in my ignorance, though,
full speed ahead!

Here are some handwaving arguments for it:

Series fields would be like winding twice as many field turns, so you
would have great low end torque, but would run out of breath as you
wound up the rpm due to back EMF. You would need less motor current,
so you wouldn't waste so many amps taking off. I think this would be
more efficient (Peukertly, if that is a word) than having both motors
in series.

Another way to think of it is going from series fields to parallel
fields is a stepped method of field weakening for higher speed (at
the expense of less torque).


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