Peter Tarver wrote:Delta-delta transformers are popular with the utilities for economy's
sake (they are less expensive than WYE transformers) For similar
reasons, some industrial applications distribute and use power within
their plants on delta feeds.In office environments, however, it's typical to use a WYE connected
secondary, i.e., 120Y/208V, for general appliance use and other WYE
connected configurations for lighting and other power.When a delta transformer is grounded, it typically occurs at either a
"corner", where two secondaries are electrically connected, or
"center-grounded" at the center of one of the secondaries. It is my
understanding that the latter case is typical for power provided to
homes in the US and is also referred to as "split-phase."Regards,
Peter L. Tarver
Nortel
[email protected]>
Delta-delta transformers are popular with the utilities for economy's
sake (they are less expensive than WYE transformers) For
similar
reasons, some industrial applications distribute and use power
within
their plants on delta feeds.
In office environments, however, it's typical to use a WYE connected
secondary, i.e., 120Y/208V, for general appliance use and other
WYE
connected configurations for lighting and other power.
When a delta transformer is grounded, it typically occurs at
either a
"corner", where two secondaries are electrically connected,
or
"center-grounded" at the center of one of the secondaries.
It is my
understanding that the latter case is typical for power provided
to
homes in the US and is also referred to as "split-phase."
Regards,
Peter L. Tarver
Nortel
[email protected]
Hi Pete
I want to address the issue of or <"center-grounded" at the center of one of the secondaries>.
Do you mean like this ?
I never encountered this yet. In this case, the voltages of the three active conductors with respect to earth would be:
V(L1)=480V*sqrt(3)/2=415V
V(L2)=480V/2=240V
V(L3)=480V/2=240V
The voltage of the imaginary center point would be about 208V. You would
have enormous leakage
currents through the Y capacitors in the power line filters.
On the other hand, as far as I remember, the IEC 38 states, that for
a TN network, one active
conductor is earthed (not stating which one). In this case I do not
see any conformance with the IEC38.
I'll be glad for any comment from the pstc community on this issue.
Best regards
George
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