Motor generator

Paul Koning paulkoning at
Tue May 4 19:01:58 CDT 2021

> On May 4, 2021, at 7:53 PM, Carlos E Murillo-Sanchez via cctalk <cctalk at> wrote:
> Donald via cctalk wrote:
>> In the deep recesses of my mind I seem to remember something about S/360
>> machines using a motor generator.
>> If I am right was this to create a stable power source at a certain
>> frequency or voltage?
> Those systems predate my experience by roughly 25-30 years.  But once you go through the trouble of adding such a thing as a motor-generator, then you can make the generator a poly-phase device (say, 12-phase) and get a much lower ripple in a full-wave polyphase rectifier; you can also easily control the output voltage by acting on the generator's rotor field current.  This sort of equipment is used for industrial processes requiring DC at thousands of amps; the polyphase setup makes it possible to leave out the output filter capacitors.

Polyphase would be complex, adding more generator windings, wires, and power transformer windings.  The usual approach instead is to increase the frequency, which is easy to do.  400 Hz is a standard frequency for applications where transformer weight is a concern, so it's found in airplanes among other things.


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