2-2-15

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. Fixed reference

The arrowhead on the end of a vector indicates ? . a.direction b.force c.negative quantity d.phase rotation

A.direction

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

Industry standards for phase rotation are ABC and CBA in a counter-clockwise direction. 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

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. Tail to tail

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. 208

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. Magnitude / direction

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

All physical quantities have magnitude and direction. Select one: True False

False

In 3-phase systems, voltage vectors of individual phases are separated by ? . a.90° b.120° c.200° d.360°

b.120°

The vector wheel graphically divides a circle into ? increments. a.10° b.20° c.30° d.40°

c.30°

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. 10"

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. Convention

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. Dead short

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. 5,250 v

Potential vectors will always point away from the ? . a.center bushing b.common point c.grounded leg d.neutral

B. Common point

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. Proportional to

In order to plot a 3-phase system or systems, one would need special tools or equipment. Select one: True False

False

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

Vectors represent physical quantities. Select one: True False

True

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

Vectors can only be drawn vertically or horizontally. Select one: True False

False

In linework, the vector lines are usually drawn without arrowheads. Select one: True False

True

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.24,912 V