UNIT 27

A delta-connected set of windings has a phase current of 10 A. The line current is _____.

17.32 A

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

480V

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 W of XL. The second load is delta-connected capacitors that have XC of 60 W. How much is the alternator phase current?

6.93 A

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

delta

In a three-phase connection, the voltage measured between the lines is the _____ voltage.

line

The alternator must supply the _____ for each of the loads.

line current

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

VARS

In a three-phase circuit, the true power (watts) is found by _____.

multiplying apparent power by the power factor

In a three-phase connection, the voltage measured across a single winding is the _____ voltage.

PHASE

A delta connected set of windings has a phase voltage of 100 V. The line voltage is _____.

100V

In calculating power in a three-phase circuit, the phase values of voltage and current are multiplied by _____.

3

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

WYE

The three-phase connection in which one end of each of the windings are connected together is called the _____ connection.

WYE

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

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

1

Often in calculations of values in three-phase systems, the square root of three occurs. The approximate value of this constant is _____.

1.732

Three-phase voltages are _____ out of phase with each other.

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 W each. What is the phase current in the alternator?

40 A

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%

The three-phase connection in which three separate inductive loads have been connected together is the _____ connection.

delta

In three-phase power systems, the delivered power _____.

never falls to zero