Exam 27: Three Phase Circuits

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.

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

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

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?

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

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

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

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

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

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

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

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

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

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

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

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

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

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.

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

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 X_L. The second load is delta-connected capacitors that have X_C of 60 Ω . How much is the alternator phase current?