27 Fundamentals of Electricity: Unit 27 - Three Phase Circuits

If three seperate coils are spaced _____ apart three voltages _____ out of phase are produced.

120%; 120%

In a balanced three-phase system, the conductors need only be about _____ the size for a single-phase two-wire system.

75%

A wye-connected alternator has a phase voltage of 277 V feeding two loads. The first load is wye connected inductors that have 60 ohm's of XL. The second load are delta connected capacitors with an Xc of 60 ohm's. The phase current in the alternator is _____ amps

BLANK

Most of the _____ generated in the world today is three-phase.

electrical power

In a three-phase connection, the voltage measured from one external voltage connector to another is the _____ voltage.

line

In a three-phase circuit, the true power is found by _____ apparent power by the _____ _____.

multiplying; power factor

In a three-phase connection, the voltage measured directly across one of the windings is the _____ voltage.

phase

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

transformer

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

wye

The three-phase connection in which all three of the coils are connected end-to-end to form a closed loop is the _____ connection.

delta

In a three-phase connection, the current that flows in an externally connected voltage conductor is the _____ current.

line

In calculating power in a three-phase circuit, the product of the _____ _____, line current, and the power factor are multiplied by the square root of three.

line voltage

Three-phase power _____ falls to zero.

never

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

1.732

A delta connected transformer has a 10 amp phase current and a _____ line current.

17.32

Correcting power factor is done with _____ connected is _____.

capacitors; parallel

Line voltage and phase voltage are the same in a _____ configuration.

delta

A delta connected three-phase alternator is driving a wye-connected resistive load. the alternator output is 480 volts. The load is 24 ohm's each. The phase current in the alternator is _____.

20

A delta connected set of windings has a phase voltage of 240 V. and a line voltage of _____.

240

A delta connection set of windings has a phase of 240 V. the line voltage is _____.

240

If a three-phase load is purely reactive, then the power will be calculated in _____.

BARS

_____ proved that three-phase power was the most efficient way electricity could be produced, transmitted, and consume.

Tesla

In calculating the power of a three-phase circuit, the product of the phase voltage, _____ _____, and power factor are multiplied by three.

phase current

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

star