Electrical 2
What function is performed by dielectric oil?
1) insulator 2) prevents moisture 3) provides cooling
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.
A delta connected set of windings has a phase voltage of 100V. What is the line voltage?
100V (DELta E=E)
3-phase voltages are ... out of phase with each other.
120° (120+120+120=360)
In calculating apparent power (VA) in a three-phase circuit, the phase values of voltage and current are multiplied by ...
3.
An open delta transformer is assembled from two 50 kVA transformers. The output power of the open delta is ...
86.6 kVA ((50+50)×.866)
The squirrel-cage rotor is constructed of ... and end ... embedded in steel laminations.
Bars; Rings
In the consequent pole motor, if the number of poles is doubled, the motor speed will be ...
Cut in half.
T or F: 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; opposite is true.
The non-rotating part of a revolving-field-typr alternator is called the ...
Stator
In a three-phase motor, the speed of rotation of the magnetic field is called the ... speed.
Synchronous
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 which configuration?
Wye (Whiiiiii)
The 3-phase connection in which one end of each of the windings are connected together is called a ...
Wye connection.
I'm a three-phase circuit, true power (watts) is found by ...
multiplying apparent power (VA) by the power factor.
A wye-delta transformer has its ... connected as wye and its ... connected as delta.
primary; secondary
Another name for the three-phase wye connection is the ... connection.
star
Line voltage and phase voltage are the same in the ... configuation.
Delta (DELta)
A delta connected set of windings has a phase current of 10A. What is the line current?
17.32A (10×square root of 3)
An open delta connection is made using ... single-phase transformers.
2.
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 frequency of the current in a squirrel-cage rotor ... as the rotor approaches synchronous speed.
Decreases
The direct current that is an input to the alternator's rotor is the ... current.
Excitation
The higher power output alternators 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 (less/more) power output and is, therefore, (less/more) often used than the revolving field type.
Less; less
If a piece of machinery needs a replacement motor and will be damaged if the new motor rotates the wrong way, the test equipment needed to test the rotation direction of the new motor is a ...
Phase rotation meter.
In a 3-phase connection, what is the voltage measured across a single winding?
Phase voltage.
The rotating part of a revolving-armature-type 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 windings are connected in ...
Series
When squirrel-cage motor is first started, the value of the current draw is ...
Several times greater than 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
Power is carried to the outside circuit of a revolving armature type of alternator via brushes riding against the ...
Sliprings
In a wye-connected system, the line voltage is higher than the phase voltage by a factor of ...
Square root of 3.
In a 3-phase connection, what is the voltage measured between the lines?
Line voltage.
In 3-phase power systems, the delivered power ...
Never falls to 0.
What is one factor that controls the output frequency of an alternator?
Number of stator poles and rotor rotation speed.
The main power distribution system of a large industrial plant is generally shown using a ... diagram.
One-line
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 windings are connected in ...
Parallel
