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Date: Wed, 04 Jun 2008 09:16:04 -0600
From: Fred Osborn <fosborn@infowest.com>
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To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: Combined Starter Alternator
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George Lendich wrote:

Directed to the electronic wiz types.
 
This is not a development issue but an educational issue as I would like 
to understand the issues associated with developing a starter alternator.
 
Personally I believe a combined starter, alternator, flywheel, damper, 
timing wheel and pick up would be a great advantage (we live to dream).
Some systems use the combined starter alternator attached to the gear 
box shaft just, between the motor and the gearbox fluid damper. 
 
I believe from talking to Bill Jepson that getting sufficient power from 
the current winding used is problematic but that there had been major 
improvements in this field. Also reading a little on the Internet ( if I 
understand it correctly) an alternator is AC ( alternating current) and 
a generator is DC. As Batteries are DC and starters are DC, we would 
need to use a DC generator winding in the starter generator (someone 
tell if I'm wrong here).
 
Of course nothing is as simple as this, so I'm keen to understand the 
issues associated - from anyone out there in the electronics world!?

George,

Do a Google search on "Switched Reluctance Motors" or "Integrated 
Starter Generators" or "Integrated Starter
Alternators. They have an advantage over permanent magnet devices in 
that they do not have the heating and
drag associated with the eddy currents of permanent magnet units. The 
IGS's are what most of the autos are using for instant starting, no idle 
at stop light, operation. The biggest hangup is the high voltage used to 
reduce the current required to get the necessary torque for an instant 
start. They do supply a pulsed DC output for battery charging from the 
same winding used for the "motor". There are more problems associated 
with the higher voltages
than you might imagine.

Fred O.