From: tkoenig@netcologne.de   
      
   Michael S  schrieb:   
   > On Fri, 26 Sep 2025 12:10:41 -0000 (UTC)   
   > Thomas Koenig  wrote:   
   >   
   >> BGB  schrieb:   
   >>   
   >> > Brings up a thought: 960VDC is a semi-common voltage in industrial   
   >> > applications IIRC.   
   >>   
   >> I've never encountered that voltage.  Direct current motors are   
   >> also mostly being phased out (pun intended) by asynchronous motors   
   >> with frequency inverters.   
   >>   
   >   
   > Are you sure?   
   > Indeed, in industry, outside of transportation, asynchronous AC motors   
   > were that most wide-spread  motors by far up to 25-30 years ago. But my   
   > imressioon was that today various type of electric motors (DC, esp.   
   > brushlees, AC sync, AC async) enjoy similar popularity.   
      
   I can only speak from poersonal experience about the industry I   
   work in (chemical).  People used to use DC motors when they needed   
   variable motor speed, but have now switched to asynchronous (AC)   
   motors with frequency inverters, which usually have a 1:10 ratio   
   of speed.  There are no DC network in chemical plants.   
      
   If you have high-voltage DC system (like in an electric car) then   
   using DC motors makes more sense.   
      
   >   
   >> > What if, opposed to each computer using its own power-supply (from   
   >> > 120 or 240 VAC), it uses a buck converter, say, 960VDC -> 12VDC.   
   >>   
   >> That makes little sense.  If you're going to distribute power,   
   >> distribute it as AC so you save one transformer.   
   >>   
   >   
   > I never was in big datacenter, but heard that they prefer DC.   
      
   Eventually, electronics requires DC.  Of course, you can make   
   an economic calculation of where you put your transformers and   
   rectifiers, and where you want which voltage.   
      
   An option which makes little sense is to have a rectifier which   
   creates high-voltage DC, then distributes that, and to have   
   an alternator at the other end to create AC which you can then   
   transform down.  It would be better to distribute AC and transform   
   it down, saving two parts.   
      
   >   
   >> >   
   >> > Or, 2-stage, say:   
   >> >    960V -> 192V (with 960V to each rack).   
   >> >    192V ->  12V (with 192V to each server).   
   >> >   
   >> > Where the second stage drop could use slightly cheaper transistors,   
   >> >   
   >>   
   >> Transistors?   
   >   
   > Yes, transistors. DC-to-DC convertors are made of FETs. FETs are   
   > transistors.   
      
   I'm more used to thyristors in that role.   
      
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