[GreenKeys] History - Why voltages andfrequencies are chosen(5v & 3.3v l...

[Ralph Mowery]

That is mainly the way we did it where I used to work.  The power company furnished us with some 13.2 KV that was stepped down from some other very high voltage.  We then sent it to about 15 or 20 other rooms in the plant  at 13.2 KV and then converted it to 480 volt 3 phase and 277 volt grounded Wye. From that we then converted it to 120 volts or 220 volts single phase.  Also for a couple of pieces of equipment there was some 208 volt 3 phase and I think it was 380 volts also to power some equipmnet. 

 That threw us to start with as the 380 volt 3 phase equipment was installed about 15 years ago and no one bothered to tell us about that odd voltage.  It was mainly for some resistance heaters that used from about 20 amps to 300 amps.  While adjusting the controlers during the checkout phase  we could not understand why they would not put out the 480 volts like many of the others and after a short search found out the equipment was only good for 380 volts so that was the voltage it was being fed with.

  ----- Original Message ----- 
  From: Sheldon Daitch 
  To: Peter Gottlieb ; WA5CAB at cs.com 
  Cc: Greenkeys at mailman.qth.net 
  Sent: Friday, November 23, 2012 6:04 AM
  Subject: Re: [GreenKeys] History - Why voltages andfrequencies are chosen(5v & 3.3v l...





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  [Most common industrial is 480/277 Wye grounded neutral. Larger facilities are "primary metered" at 13.8 kV and get better rates as the company bought and maintains MV switchgear and transformers. ]

  Another reason to meter on the primary side, is that the customer eats (pays for) the losses in the transformers.


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