Electrical 2

Three-phase voltages are _________ out of phase with each other

120 degrees

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

17.32 A

In the consequent pole motor, if the number of poles is doubled, the motor speed will be __________

Cut in half

The direct current that is an input to the alternator's rotor is the _________ current

Excitation

The frequency of the current in a squirrel-cage rotor _________ as the rotor approaches synchronous speed.

Decreases

The main power distribution system of a large industrial plant is generally shown using a _________ diagram

One-line

A delta connected set of windings has a phase voltage of 100 V. What is the line voltage?

100 V

A squirrel-cage rotor induction motor has a synchronous speed of 3600 RPM and an actual rotor speed of 3450 RPM. What is the percent slip?

4.17% synchronous speed minus actual speed Divided by synchronous speed x 100

A wye-connected secondary has a phase voltage of 277.14 V. What is the line voltage?

480 V

What function is performed by dielectric oil?

Acts as an insulator Prevents moisture formation Provides cooling

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

Three

An open delta connection is made using _____ single-phase transformers.

Two

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

VARs

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 a _________ connection

WYE

Line voltage and phase voltage are the same in the __________ connection

Delta

Some motors are constructed so that they will operate on either of two voltages. When they are connected to operate on the lower of the two voltages, the phase windings are connected in

Parallel

If a piece of machinery needs a replacement motor and will be damaged if the new motor rotated the wrong way. The test equipment needed to test the rotation direction of the new motor is a ____________

Phase rotation meter

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

Phase voltage

A wye-delta transformer has its _________ connected as a wye and its _________ connected as a delta

Primary; secondary

The rotating party of a revolving-armature-type of alternator is called the _____________

Rotor

Some motors are constructed so that they will operate on either of two voltages. When they are connected to operate on the higher of the two voltages, the phase windings are connected in

Series

A wye-delta transformer has a primary voltage of 7200 V and a secondary voltage of 360 V. What is the turns ratio?

11.55 : 1

An open delta transformer is assembled from two 150 kVA transformers. The output power of the open delta is _____.

259.8 kVA

A delta-wye transformer has a turns ratio of 9:1. The primary line voltage is 3600 V. What is the secondary line voltage?

692.8 V

A wye-delta transformer has a primary line voltage of 7200 V and a secondary line voltage of 480 V. What is the turns ratio?

8.66 : 1

An open delta transformer is assembled from two 50 kVA transformers. The output power of the open delta is _____.

86.6 kVA

What machines operate on the same principle of electromagnetic induction as DC generators, but they have no commutator?

Alternators

To reverse the direction of rotation of a three-phase motor, reverse ____________

Any two leads

The squirrel-cage rotor is constructed of _________ and end __________ embedded in steel laminations

Bars ; rings

Power is carried to the outside circuit of a revolving armature type of alternator via brushes riding against the __________

Commutators

To minimize interference, telecommunication cables are run as close to phase conductors as possible and as far away from the neutral conductor as possible.

False

The higher power output alternator use a revolving __________

Field

In three-phase transformer connections, the primary leads are labeled with the letter __________ and the secondary leads are labeled with the letter _________

H ; X

The wound-rotor induction motor is popular in industry because it has ________ starting torque and _________ starting current.

High ; low

The revolving armature type of alternator is capable of __________ power output and is, therefore, ____________ often used than the revolving field type.

Less ; less

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

Line voltage

In three phase power systems, the delivered power _____________.

Never falls to zero

What is one factor that controls the output frequency of an alternator?

Number of stator poles and rotor rotation speed

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

When a squirrel-cage motor is first started, the value of current draw is ____________

Several times the running current

Three lines supply power to a three-phase motor. If one of these lines should open, the motor will be connected to single-phase power. This condition is known as ___________

Single-phasing

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

Square root of 3- 1.73

The non-rotating part of a revolving-field-type alternator is called the ___________

Stator

In a three-phase motor, the speed of rotation of the magnetic field is called the _________ speed.

Synchronous