Such transformers were often used in permanent installations of phase-control dimming systems. At Production Arts, we regularly specified delta-wye transformers with 208V primaries and 133/230V secondaries. This was useful in large systems with potentially long branch
circuit runs. Modern dimming systems such as
ETC Sensor allowed setting a maximum scale
voltage on a per-circuit basis. This allowed long runs with
conductor size no larger than 10AWG to achieve 120V at the
outlet, compensating for I-squared-R losses in the
dimmer choke and branch
circuit conductors, as well as zero-crossing deadtime and
SCR drop in the
dimmer itself.
These transformers were typically K-rated, and had 1% adjustment taps above and below the nominal
voltage to accommodate variations in utility
power delivery.
The situation got a
bit more complex due to changing trends:
A. Non-dimmed
power delivery through
relay or constant breaker-only circuits. This eliminated the
voltage drop of the
dimmer and
choke and could result in undesirably high
voltage at the
outlet.
B. The appearance of 115V lamps such as the
HPL, which sought to deliver normal brightness of lamps while compensating for
dimmer and
choke drop.
As to your description of a
transformer like this in a
portable system, it's hard to imagine the advantages.
ST
