DEL 27 Flashcards
In a three-phase connection, what is the voltage measured between the lines?
line voltage
The alternator must supply the _____ for each of the loads.
line current
A delta connected set of windings has a phase voltage of 100 V. What is the line voltage?
100 V
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?
40 A
If a three-phase load is a pure reactive load, then the power calculated has units of _____.
VARs
In a wye-connected system, the line voltage is higher than the phase voltage by a factor of _____.
square root of three
Line voltage and phase voltage are the same in the _____ connection.
delta
In a three-phase connection, what is the voltage measured across a single winding?
phase voltage
In a three-phase circuit, the true power (watts) is found by _____.
multiplying apparent power by the power factor
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
In a balanced three-phase system, the conductors need be only about _____ the size of conductors for a single-phase, two-wire system of the same kilovolt-ampere (kVA) rating.
75 percent
The three-phase connection in which one end of each of the windings are connected together is called a(n) _____ connection.
wye
In calculating apparent power (VA) in a three-phase circuit, the phase values of voltage and current are multiplied by _____.
three
A three-phase connection in which three separate inductive loads have been connected together is a(n) _____ connection.
delta
Three-phase voltages are _____ out of phase with each other.
120 degrees
Line current and phase current are the same in the _____ configuration.
wye
A delta-connected set of windings has a phase current of 10 A. What is the line current?
17.32 A
In three-phase power systems, the delivered power _____.
never falls to zero
A delta connected set of windings has a phase voltage of 480 V. What is the line voltage?
480 V
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.
150 percent
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
