T&T: Why the Wye? (2 30a to 1 50a/240)

[Peter Bennett]

Friday, September 18, 2009, 7:09:20 PM, Ken wrote:


KB> Here is the math:

KB> *Dual 30 amp cords have*
KB> Cord #1 has 125 volts x 30 amps =  3,750 watt capability
KB> Cord #2 has 125 volts x 30 amps =  3,750 watt capability
KB> Total capability is 3,750 + 3,750 =  7,500 watts (or 7.5 kw)

KB> *Single 50 amp cord has*
KB> Red wire has 125 volts x 50 amps =  6,250 watt capability
KB> Black wire has 125 volts x 50 amps =  6,250 watt capability
KB> Total capacity is 12,500 watts (or 12.5 kw)
KB> White wire is happy at 180 degree phase relationship as the current 
KB> cancels.  So, max current in white can not exceed 50 amps.

KB> Hope this has made the issue as clear as mud, or perhaps a little better.

KB> Cheers,
KB> Ken.


Just to be pedantic:  The connectors are rated by the electrical code
as 125 or 250 volt, but the actual voltage in the circuits should be
120 or 240 volts, which reduces the power in the above calculations to
3600 watts, 7200 watts (7.2 KW), 6000 watts or 12000 watts (12 KW).

-- 
Peter Bennett, VE7CEI    Vancouver, B.C., Canada
Ennos 31 "Honeycomb"
GPS and NMEA info: http://vancouver-webpages.com/peter 
Vancouver Power Squadron: http://vancouver.powersquadron.ca