Gorilla Solar Question: how to deal with 3-phase feed from pole - Page 7

 
| There is another connection commonly used in industry.  Draw your coils again,
| except arrange them in a "star" configuration.  One end of each coil is
| attached to all the others.  This is the neutral.  Each coil is good for 120
| volts.  Two coils are good for 120*sqrt(3) = 208.  A wire from each of two of
| the coils and one from the neutral form the familiar 3 wire service, only this
| time it is 120/208 volts.

It is almost exclusive for new installations now days.  Many utilities make
it hard or impossible to get delta.  You have to have 208Y/120, 480Y/277, or
600Y/347 in this voltage class.  I've seen one utility that also offered a
240Y/139 system presumably to support all those old 240 volt 3-phase motors.

--
|WARNING: Due to extreme spam, googlegroups.com is blocked.  Due to ignorance |
|         by the abuse department, bellsouth.net is blocked.  If you post to  |
|         Usenet from these places, find another Usenet provider ASAP.        |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |

  Delta systems are not meterable accurately and most system providers are
trying to rid their system of it, despite what Blondell stated when 5%
accuracy was acceptable.

Also delta systems need to be insulated to carry large common-mode voltage
swings with primary voltages bleeding through the winding capacitances and
stray influences breaking down insulations. Not to mention one customer
grounding a phase and another customer's equipment starting on fire from it.

Wye systems have their own problems and many farm animals (not Neon John)
don't like it.

 Solar Flare wrote:

Rubbish.  If you can accurately meter three-phase three-wire systems, it
doesn't matter if the source is wye or delta.  The only trouble is that
accurately metering three-phase unbalanced load requires more than just a
single, single-phase meter.  Something the average residence service doesn't
use.  But industrial installations have been doing it for generations,
Blondell not-withstanding.

daestrom

 Sorry. You are out of date.

Metering a current with a voltage that may or may not be phase or magnitude
related is not an accurate method capable of passing todays stricter
standards required in Canada. The whole system has to meter at better than
1% accuracy and that means after instrument transformer inaccuracies the
meter and method needs to be better than 0.5%, usually.


Your guess method doesn't meet the standards, anymore with an unbalances
system. Some of the HV lines crossing Ontario have seasonal 2 degree shifts
in one phase and that disqualifies accurate metering on delta systems. Not
happening anymore

 Better luck next guess.

 
wrote:

triangle,

supply.

center-tapped or

horizontal

majority of

Wow, I was actually able to follow all that in my head without drawing it.
You guys are doing a good job educating me.


either of your wives.