31.1
Power is carried to the outside circuit of a revolving armature type of alternator via brushes riding against the _____.
slip ring
The non-rotating part of a revolving-field-type alternator is called the _____.
field
The rotating part of a revolving-armature-type of alternator is called the _____.
rotor
To reverse the direction of rotation of a three-phase motor, reverse _____.
any two leads
When a squirrel-cage motor is first started, the value of the current draw is _____the running current.
higher
What machines operate on the same principle of electromagnetic induction as DC generators, but they have no commutator?
alternators
The direct current that is an input to the alternator’s rotor is the _____ current.
excitation
Alternators of small kilovolt-ampere rating are generally _____-cooled.
air
The set of squirrel-cage bars on the rotor of a synchronous motor is used to start the motor and is known as the _____.
amortisseur winding
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
An alternator that has a separate small alternator mounted on the shaft of its rotor is equipped with a(n) _____.
brushless exciter
Using ________ for cooling alternators has the advantage of lower density reducing the windage loss of the spinning rotor.
hydrogen
Hydrogen cooling is often used with what type of alternator?
large-capacity
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%
The frequency of the current in a squirrel-cage rotor _____ as the rotor approaches synchronous speed.
decreases
In order to increase the efficiency of the cooling, some alternators operate in a(n) _____ atmosphere.
hydrogen
. The higher power output alternators use a revolving _____.
field
The direction of magnetic field rotation is known as _____ rotation.
phase
In a three-phase motor, the speed of rotation of the magnetic field is called the _____ speed.
synchronous
The torque of a squirrel-cage induction motor will be maximum when the phase angle between the stator and rotor fields is _____.
0 degrees
What is one factor that controls the output frequency of an alternator?
number of stator poles and rotor rotation speed
A three-phase alternator containing six poles is turning at 1000 RPM. What is the output frequency?
50 Hz
Using a(n) _____ is one method of preventing induced voltage from becoming excessive.
field discharge resistor
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
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