transformer 3 phase connections Flashcards
The voltage across a transformer winding in a delta system is ?
equal to the voltage from line to line
The line-to-line voltage in a wye system is ? the voltage across the transformer windings of a wye connected bank.
1.73times greater than
Vector lines are joined from head to tail in delta systems.
true
Wye-wye and delta-delta transformer banks can have either a 0° or ? angular displacement.
180 degree
The voltage across a wye connected transformer coil is ? of the line-to-line voltage on the wye system.
58%
Transformers with single primary bushings may be used to construct wye-wye banks.
true
Transformers with secondary voltage ratings of 120/240 volts are banked to supply 3-phase 208-volt power on a 4-wire service line. The secondary coils must be connected in ? banks.
parallel and wye
Transformers installed on a 12.5-kilovolt, 4-wire circuit must have a nameplate primary voltage rating of ? when the primary is banked in a wye.
7200/12470 y
In a vector line drawing of a wye bank, if the head of a vector line comes in contact with the tail of another vector line, it will be a dead short.
true
The primary and secondary vector lines of an individual transformer are always at the same angle and point in the same direction.
true
If transformer primary windings are delta banked on a 4.16-kilovolt, 4-wire primary circuit, the primary nameplate voltage rating must be ?
4160/2400 v
In a wye banked secondary circuit, the star point leads from the X bushings of the outboard transformers carry only the load imbalance and may be of reduced size.
false
Only transformers with two primary bushings can be used to supply 3-phase power when the primary circuit is delta connected.
true
The secondary windings of a transformer with voltage ratings of 120/240 volts must be connected in series to supply 208-volt, 3-phase power on a 4-wire service line.
false
