Unit 26
40 A
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?
phase voltage
In a three-phase connection, what is the voltage measured across a single winding?
Square root of three
In a wye-connected system, the line voltage is higher than the phase voltage by a factor of _____.
Wye
The three-phase connection in which one end of each of the windings are connected together is called a(n) _____ connection.
three
In calculating apparent power (VA) in a three-phase circuit, the phase values of voltage and current are multiplied by _____.
One
When calculating the power of a pure resistive load, the voltage and current are in phase with each other and the power factor is _____.
VARs
When calculating the power of a pure resistive load, the voltage and current are in phase with each other and the power factor is _____.
Multiplying apparent power by power factor
In a three-phase circuit, the true power (watts) is found by _____.
150 percent
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.
120 degrees
Three-phase voltages are _____ out of phase with each other
100 V
A delta connected set of windings has a phase voltage of 100 V. What is the line voltage?
Delta
A three-phase connection in which three separate inductive loads have been connected together is a(n) _____ connection.
Never falls to Zero
In three-phase power systems, the delivered power _____.
Wye
Line current and phase current are the same in the _____ configuration.
Delta
Line voltage and phase voltage are the same in the _____ connection.
Line current
The alternator must supply the _____ for each of the loads.
480 v
A delta connected set of windings has a phase voltage of 480 V. What is the line voltage?
17.32 A
A delta-connected set of windings has a phase current of 10 A. What is the line current?
6.93 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?
star
Another name for the three-phase wye connection is the _______________ connection.
75 percent
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.
Line voltage
In a three-phase connection, what is the voltage measured between the lines?
