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Re: Explain 3 Phase



Original poster: "Eric Davidson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <edavidson-at-icva.gov>

Hi All,

One more time.....  The electrical service supplied to 99.9% of American
homes is single phase, 120/240 volt, 3 wire service.  Single phase means ONE
phase...period....not 2 phases 180 degrees apart.  The service enters the
house via a cable comprising two insulated (hot or line) conductors wrapped
around an uninsulated, grounded, neutral conductor.  The neutral conductor
is connected to the midpoint of the secondary winding on the distribution
transformer on the pole or the pad and connected solidly to ground.  The
voltage between the two line conductors is 240 and between either line and
neutral is 120.  The function of the neutral conductor is to carry the
unbalanced portion of the load.  If you had only identical 100 watt, 120
volt light bulbs as the only loads in your house, and they were evenly
distributed so the same number of bulbs ran on each line conductor, the
neutral conductor would carry no current.  The two line conductors are of
opposite POLARITY compared to the neutral conductors.  The same situation
exists on a Y connected 3-phase bank.  The neutral is grounded for safety
reasons.  One of which is that the maximum voltage from line to ground in
your home is 120 volts.  So, even if you stuck your finger in a 240 volt
dryer outlet, you would feel a 120 volt shock, provided you had good contact
with the ground.  To experience 240 volts you have to stick both fingers in
the outlet.  DON'T TRY THIS!  Hope this helps.  Coil safe!

Eric
edavidson-at-icva.gov


 ----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Friday, April 27, 2001 8:55 AM
Subject: Re: Explain 3 Phase


> Original poster: "Millipede by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<millipede-at-carolina.rr-dot-com>
>
> 3 phase power in the US is  three 60 hertz (cycles per second) signals set
> at 120 degrees apart. Thus when cycle A is peaking, cycle B is 120 dgrees
> behind it and cycle C is 240 degrees behind A. Your house power is usually
> supplied with 240 volt main...which is actually two 120 volt signals that
> are 180 degrees oout. So when A is peaking positive, B is peaking
negative.
> THerefore you have a difference in voltage of 240 V. Your wall sockets
have
> one of the wires from the 240 paired with a neutral wire to get you 120V.
So
> basicly, you are gettin one phase. You can do this with a 3 phase system
> also.
> Hope this helps.
> Robert
> ----- Original Message -----
> From: Tesla list <tesla-at-pupman-dot-com>
> To: <tesla-at-pupman-dot-com>
> Sent: Sunday, April 22, 2001 7:07 AM
> Subject: Explain 3 Phase