Thanks Don,
From your descriptions (very well done), it seems that Delta is a
specialized config where that type of output would be the advantage. I
can't think of a use at this time but, It's good to have options.
Randy
<yuyub.429814$9l5.56875@pd7tw2no>...
:
:
:
: : > Greetings,
: >
: > This question concerns the configuration of an AC genny stator. I like
the
: > Idea of a single common lead and I understand Wye. Delta, on the other
: > hand, I'm a little unclear about especially causing it to short by
: improper
: > hookup. What are the advantages?
: >
: > An Inquiring mind,
: > Randy Gross
: >
: ---------
: For most cases the Y has the advantage in that the output is not floating
as
: in a delta and it is also possible to draw single phase loads - i.e. 120V
: phase to neutral and 208 phase to phase for 3 phase loads. Most large
: generators are Y as the insulation needs are a bit less and one can
detect
: ground faults.
: A delta is essentially an ungrounded system and for low voltage
situations
: one phase can go to ground accidentally with no problem. Single phase
loads
: have to be at the voltage from phase to phase (i.e. a 240V delta -allows
: 240V single phase on any pair of terminals) If you want a 120V/240V load,
: then one phase must be center tapped and that tap is usually grounded.
that
: means you can't do the same on the other phases.
: The delta winding has lower currents in the phase windings but the
voltage
: of the winding is higher (both by a factor of root(3). There is then a
: balance between insulation, turns per winding and conductor size. For
higher
: voltages, this favours Y.
: There is a difference in the case of third harmonics. The delta provides
a
: path for third harmonics but this is of more importance in transformers
than
: generators.
: As far as shorting is concerned: With a proper connection, the voltages
of
: the three phases cancel when one looks at the loop formed by the
connection.
: If one of the windings is reversed, then this cancellation doesn't occur
and
: the voltage source seen by the loop (triangle) of the windings will be
twice
: the phase voltage causing high short circuit currents to flow in the
loop.
: Normal : Va +Vb +Vc = 1 +(-0.5 -j0.866) +(-0.5 +j0.866) = 0
: reversed: Va +Vb -Vc =1 +(-0.5-j0.866) -(-05+j0.866) =1-j1.73 (magnitude
: =2)
: Draw the phasors.
: --
: Don Kelly
:
[email protected]
: remove the urine to answer
:
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