RK05 spindle pulleys - trade 50Hz vs 60Hz?

[Chuck Guzis]

On 07/26/2018 07:54 AM, Anders Nelson via cctalk wrote:
> To get that power, did they have to use a rotary convertor from 60Hz
> 3-phase to get 400Hz?
> 
> https://en.wikipedia.org/wiki/Rotary_converter

As Paul mentioned, less a "rotary converter" than a AC motor-AC
generator hookup.  One advantage is that the rotational inertia in such
a setup does have the ability to smooth over small power disruptions.

Such MG setups were very common in industry before modern
semiconductors.  When I had a summer job showing movies at a drive-in
theater (a long time ago), the supply for the carbon-arc lamps was a
40hp motor powered by 3-phase 60Hz, driving a DC generator.  In WWII
radio equipment, MGs in a unitzed form called "dynamotors" were used to
supply the high-voltage anode voltage for the tubes.  Electroplating
shops similarly used large DC generator setups to supply plating current.

3 phase full-wave rectified AC has approximately 87% DC content at 6x
the supply frequency.  So for 400Hz, the ripple is only 13 percent at
2400 Hz before filtering.

--Chuck