From: peterwieck33@gmail.com   
      
   As an aside, I toured the Veolia Steam Plant in Philadelphia, yesterday. This   
   plant has been in continuous operation since it opened in 1909, and is quite a   
   remarkable place. I got to be up-close-and-personal with the equipment,   
   including the steam and    
   gas turbines, the boilers, pumps, controls, switchgear, powerhouse and uplink.    
      
   Standing under the main step-up transformer (2,300 VAC to 23,000 VAC) is a   
   truly visceral experience. Once one feels that level of "HUM", one will never   
   mistake 60 for 120 ever again.    
      
   Relevance:    
      
   60 HZ hum suggests a bad or failing rectifier.    
   120 HZ hum suggests bad or failing filter caps.    
   50 & 100 for our Euro and Asian friends.    
      
   Amazing amount of mechanical-feedback devices in use in these plants - it   
   seems that VFDs and  great many "modern" grid-tie devices are simply not   
   sufficiently rugged or reliable at this scale.    
      
   Peter Wieck   
   Melrose Park, PA   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)