3-1-11 Transformers—Three-Phase Voltages Flashcards
The two primary systems used by the electrical industry are three phases connected in wye or delta.
True
According to this lesson, there are __?__ basic transformer connections that can be derived from the two, three-phase systems in use today.
6
The simplest of the 3-phase systems is the __?__.
delta
Each side of the triangle in a delta system represents the amount of voltage on the lines.
True
The most commonly used 3-phase system is called the __?__.
star (wye)
The voltage from the tip to the center of the wye in a wye connection is the __?__ voltage.
phase
In the wye system, __?__ voltage(s) are available.
2
Wye systems are also called __?__-wire systems.
4
In a wye system, the line voltage is __?__ times the phase voltage.
1.73
One of the earliest electrical systems is the __?__ delta.
2400 V
By converting a 2,400-volt delta system to a 4,160-volt wye system, the circuit loading can be increased by __?__ with the same line current as before.
73%
The square root of __?__ is needed to calculate delta currents and wye voltages.
3
If the voltage phase to ground is 2,400, the phase to phase voltage is __?__. (round off)
4160
Two lines that have the same rotation will always phase together.
False
A third harmonic can be as much as __?__ larger than the phase voltage.
150%
If the windings of a generator or transformer bank are connected together at one end, the connection is a __?__.
wye
In a 3-phase system made up of three equal voltages, the phases are separated by a phase angle of __?__.
120%
An electrical distribution scheme that employs only one source of voltage is single-phase.
True
Polyphase systems can have up to __?__ individual voltages.
12
One drawback of generating single-phase voltage is that the pulsing of the power output causes excessive physical stress on the __?__.
generator
In a 3-phase system, the three voltages are of different magnitudes.
False
If B phase is lagging A phase by 120°, C phase would lag A phase by __?__.
240°
An equilateral triangle is equal to the square root of three multiplied by __?__.
one of the neutral voltages
In 3-phase production, the output power __?__.
remains constant
The horsepower rating of 3-phase motors is __?__ greater than a single-phase motor of the same physical size.
150%
A 3-phase system needs wires that are 75% larger than a single-phase two-wire system.
False
