Delmars Unit 26 Three-Phase Circuits

Réussis tes devoirs et examens dès maintenant avec Quizwiz!

The alternator must supply the _____ for each of the loads. capacitance line current inductance voltage

line current

What does IL(Load) represent? phase current of the load phase voltage of the alternator phase voltage of the load line current of the load

line current of the load

In a three-phase connection, what is the voltage measured between the lines? line voltage phase voltage

line voltage

In three-phase power systems, the delivered power _____. falls to zero three times per cycle falls to zero once per cycle never falls to zero falls to zero at least three times per cycle

never falls to zero

When calculating the power of a pure resistive load, the voltage and current are in phase with each other and the power factor is _____. one two three four

one

Load 1 consists of three resistors with a resistance of 6 ohms each, connected in wye and the phase voltage is less than the line voltage by a factor of 1.732. What is the phase current? 56 A 96.992 A 40.416 A 53.888 A

53.888 A

Which of these formulas is used to calculate total current delivered by the alternator?

IL(alt)=

The circuit power factor is the ratio of apparent power and true power. True False

True

If a three-phase load is a pure reactive load, then the power calculated has units of _____. VA W VARs

VARs

Line voltage and phase voltage are the same in the _____ connection. delta wye

wye

Which type of load is the above image depicting? wye delta

wye picture has 240V

What does EL(Load) represent? phase current of the load phase voltage of the alternator phase voltage of the load line voltage of the load

line voltage of the load

What does IP(Load) represent? phase current of the load phase voltage of the alternator phase voltage of the load line voltage of the load

phase current of the load

In a three-phase connection, what is the voltage measured across a single winding? line voltage phase voltage

phase voltage

What does EP(Load) represent? phase current of the load phase voltage of the alternator phase voltage of the load line voltage of the load

phase voltage of the load

In a wye-connected system, the line voltage is higher than the phase voltage by a factor of _____. square root of two square root of three two three

square root of three

Load 2 is formed from three inductors in a delta with an inductive reactance of 10 ohms each. What is the phase current? 56 A 96.992 A 40.416 A 53.888 A

56 A

Which of these formulas is used to calculate three-phase watts of a three-phase power circuit?

P=

Which of these formulas is used to calculate circuit power factor?

PF=

When Load 2 is made up of inductors, the reactive power can be calculated using the line values of voltage and current supplied to the load. True False

True

In calculating apparent power (VA) in a three-phase circuit, the phase values of voltage and current are multiplied by _____. three four five six

three

The horsepower rating of three-phase motors and the kilovolt-ampere rating of three-phase transformers are about _____ greater than for single-phase motors or transformers with a similar frame size. 75% 100% 150% 200%

150%

A delta connected set of windings has a phase voltage of 480 V. What is the line voltage? 277.14 V 480 V 831.36 V 1440 V

480 V

A delta connected set of windings has a phase voltage of 100 V. What is the line voltage? 57.7 V 100 V 173.2 V 300 V

100 V

A delta-connected set of windings has a phase current of 10 A. What is the line current? 5.77 A 10 A 17.32 A 30 A

10A

Three-phase voltages are _____ out of phase with each other. 80° 90° 100° 120°

120°

A delta-connected three-phase alternator is driving a wye-connected resistive load. The alternator output voltage is 480 V. The load resistors are 12 Ω each. What is the phase current in the alternator? 13.33 A 23.09 A 39.28 A 40 A

40 A

Load 3 is formed from three capacitors with a capacitive reactance of 8, connected in a wye and the phase voltage isless than the line voltage by a factor of 1.732. What is the phase current? 56 A 96.992 A 40.416 A 53.888 A

40.416 A

A wye-connected alternator that has phase voltages of 277 V is feeding two loads. The first load is wye-connected inductors that have 40 Ω of XL. The second load is delta-connected capacitors that have XC of 60 Ω. How much is the alternator phase current? 6.93 A 14.93 A 24.62 A 28 A

6.93 A

In a balanced three-phase system, the conductors need to be only about _____ the size of conductors for a single-phase, two-wire system of the same kilovolt-ampere (kVA) rating. 25% 30% 50% 75%

75%

When determining the amount of capacitance needed to correct power factor, what is the first step? Determine the capacitance value of each capacitor. Determine the reactive power of the circuit. Determine the apparent power of the circuit. Determine the power of the circuit.

Determine the apparent power of the circuit

When resistors of Load 1 are connected in a delta, the line current is the same as the phase current. True False

False

Another name for the three-phase wye connection is the _______________ connection.

Star

IL(Load 1) represents the line current to Load 1 (resistive). True False

True

If Load 1 is pure resistive, true power can be calculated using the line and phase current values. True False

True

If Load 3 is pure capacitive, the current and voltage are 90 degrees out of phase with each other and the power factor is zero. True False

True

Line current and phase current are the same in the _____ configuration. delta wye

delta

In a three-phase circuit, the true power (watts) is found by _____. multiplying line voltage by line current multiplying apparent power by the power factor dividing power factor by the apparent power multiplying phase voltage by phase current

multiplying apparent power by the power factor

The three-phase connection in which one end of each of the windings are connected together is called a(n) _____ connection. delta wye open delta open wye

wye

If the phase windings of the alternator are connected in a wye, the phase current is the same as the line current. True False

True

Which of these formulas is used to calculate apparent power of a three-phase power circuit?

VA=

A three-phase connection in which three separate inductive loads have been connected together is a(n) _____ connection. delta wye open delta open wye

delta

Which type of load is the above image depicting? wye delta

delta picture shows 480V


Ensembles d'études connexes

Medical-Surgical Nursing Week 7 Part 1

View Set

ISA 301 Lecture 3 - Transport and Application Layer Services

View Set

PrepU Chapter 25: Growth and Development of the Newborn and Infant

View Set

explain the difference between accuracy and precision

View Set

LESSON 4 - Interpersonal Skills in Organizations 7e

View Set

201 Tragedy of the commons and econ notes

View Set