[Boatanchors] Basic electricity question

[Gary Schafer]

Hi Robert,

I thought I was covering all my bases. I did say "no neutral required". :>)
But, if a neutral is used in a Y 3 phase then the part of the load that 
uses the neutral is not a 3 phase load but a single phase load. :>)

73
Gary  K4FMX


WA5CAB at cs.com wrote:
> Not necessarily so.  It depends on how the transformer or generator is 
> configured (Delta or Wye/Star) and on the load.  Many three-phase loads like welding 
> machines, HV power supplies for KW and above transmitters (required BA 
> content), etc. will have single phase auxiliaries like relays, blowers, etc.  Often 
> enough these are low voltage rather than high voltage (i.e., if the three 
> phase distribution is wired 120/208 Wye they may be cheaper 120 volt units) and 
> will require the neutral.  
> 
> Delta distribution systems in plants are not common except in special 
> circumstances (we once had a pipe coating plant where the compressor pad was wired 
> Delta to run six 150 HP compressors).  The more common Wye configured systems 
> are five-wire systems (three hot, neutral and ground), even if the majority of 
> three-phase loads (motors) don't need the neutral.  Plus it is common in 
> industrial buildings that need both single and three-phase power to run 120/208 Wye, 
> taking all the single phase 120 loads from line to neutral, single phase 240 
> volt loads (with taps appropriately set) line to line, and three phase loads 
> from line to line to line.  Same with 288/440 distribution.  3-phase 440 loads 
> run line to line to line and building lighting (288 volt) runs line to 
> neutral, with the total lighting load in the building being evenly distributed over 
> the three phases.
> 
> In a message dated 1/13/2005 8:44:11 PM Central Standard Time, 
> garyschafer at comcast.net writes: 
> 
>>3 phase power as described by others can be thought of as 3 separate hot 
>>lines. No neutral required. 
> 
> 
> Robert & Susan Downs - Houston
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