[cctalk] Re: mainframe vs mini

Yes I can concur with this. I operate some Navy transmitters (at home) and while on the vessel they used 3 phase power supplies which were physically smaller and produced less ripple. At home, I use a 1 phase power supply just fine. These were 1KW output (4KW input) transmitters so not a lot of power but benefitted from low ripple. 73 Eugene W2HX -----Original Message----- From: Paul Koning via cctalk &lt;cctalk(a)classiccmp.org&gt; <snip> But apart from circular motion (i.e., feeding motors) there is a second reason to use three phase power: reduced ripple. Full wave rectification of n Hz mains power gives you a 2n Hz ripple; full wave rectification of 3-phase n Hz mains produces a 6 Hz ripple, and tha amplitude is a lot less as well. So the filters are much smaller, which is a non-trivial matter if you need to filter several hundred amps. That of course assumes your power supplies are actually fed off the three phase mains, rather than being individual single phase supplies spread over the phases. The former was certainly the case with the CDC 6600, you can see it clearly in the schematics. paul