Unit 2-2 Lesson 15
If a vector is drawn to represent 480 volts and is scaled where 1/4 inch equals 12 volts, the line will be ? long. a. 10" b. 12" c. 14" d. 16"
A
In a delta configuration, if a plus-minus combination comes in contact with another plus-minus combination, a(n) ? will result. a. dead short b. normal connection c. open circuit d. point of twice the current
A
Once a ? for vectoring has been established, it must be maintained throughout a vectoring exercise. a. convention b. current c. sine wave d. voltage
A
The arrowhead on the end of a vector indicates ? . a. direction b. force c. negative quantity d. phase rotation
A
To represent a wye connection, the vectors are connected ? . a. tail to tail b. tail to tip c. tip to tail d. tip to tip
A
To vector a 3-phase system, it is essential to establish a ? of the phases. a. fixed reference b. given order c. sine wave d. vector wheel
A
If a 3/4-inch vector line represents 750 volts, a line 5 1/4 inches long represents ? . a. 4,170 V b. 5,250 V c. 6,890 V d. 7,210 V
B
If a system uses 14,400-volt transformers connected phase-to-ground, the system voltage phase-to-phase is ? . a. 22,000 V b. 24,912 V c. 32,310 V d. 36,400 V
B
If the secondary of a 3-phase bank is connected 120 wye, the voltage phase-to-phase is ? . (Round the answer to the nearest whole number.) a. 136 V b. 208 V c. 246 V d. 312 V
B
In 3-phase systems, voltage vectors of individual phases are separated by ? . a. 90° b. 120° c. 200° d. 360°
B
Potential vectors will always point away from the ? . a. center bushing b. common point c. grounded leg d. neutral
B
The length of a vector line is ? the magnitude of the vector quantity. a. one-half b. proportional to c. the opposite of d. the same as
B
The vector wheel graphically divides a circle into ? increments. a. 10° b. 20° c. 30° d. 40°
C
Transformer output voltages have ? , ? phase angle, and phase sequence. a. current / voltage b. current flow / voltage peaks c. direction / current flow d. magnitude / direction
D
In a star system, the phase angle displacement through a transformer bank (primary to secondary) is either 0° or 160°. Select one: True False
False
In order to plot a 3-phase system or systems, one would need special tools or equipment. Select one: True False
False
Phase position and phase sequence (rotation) are usually established at the point of service to the customer. Select one: True False
False
Vectors can be added, but they cannot be divided. Select one: True False
False
Vectors can only be drawn vertically or horizontally. Select one: True False
False
All physical quantities have magnitude and direction. Select one: True False
True
Graphical illustrations using vectors show direction and magnitude. Select one: True False
True
In a delta configuration, the pointed plus end of one arrow (vector) makes contact with the negative tail of the next arrow. Select one: True False
True
In linework, the vector lines are usually drawn without arrowheads. Select one: True False
True
Industry standards for phase rotation are ABC and CBA in a counter-clockwise direction. Select one: True False
True
Knowing the vector displacement of a bank becomes critical when paralleling 3-phase banks. Select one: True False
True
One advantage of completing a vector drawing of a 3-phase bank prior to physically building it is that it ensures the bank will be built in a logical fashion. Select one: True False
True
Vector is the term for lines that represent relationships between phases. (The term phasor is used in electrical drawings.) Select one: True False
True
Vectors represent physical quantities. Select one: True False
True
