Electrical 11

Because some of the input energy to the alternator ends up being converted into heat, often cooling is required. The main types of cooling media are

air and hydrogen

Two alternators are being connected to supply power to a load. After the connection is made, in order to make the added alternator share the load, the input torque to the alternator being added must be

increased

The __ winding is made of a few turns of large wire and is located at the bottom of the stator core

run

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

several times the running current

In the shaded pole motor, the shading coil acts like a(n) ___ transformer secondary

shorted

Selsyn motors operate on ___ phase voltage

single

In order to parallel two alternators, they must be producing the same voltage, have the same phase rotation and be in phase. To check the phase angle difference, you can use a test set called a(n)

synchroscope

A two-phase power system has two voltages which are

90* out of phase

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

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

any two leads

In the consequent pole motor, when the polarity of half of the pole windings is reversed, thery effectively doubling the number of poles, the motor speed will

cut in half

In an alternator, when the rotor DC excitation current is removed there is a possibility of damaging high voltages being developed. In order to limit voltage and thereby prevent damage, a __ or a diode can be included in the circuit

field discharge resistor

The output shaft of a stepping motor

moves through a specific angle for each input pulse

The output frequency of an alternator is controlled by the

number of stator poles and rotor rotation speed

If one alternator does not produce sufficient power to supply a load, another alternator can be connected to the circuit. The second alternator is connected in

parallel

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

In a three-phase alternator, the direction of magnetic field rotation is also called

phase rotation

Conductive compensation is accomplished by connecting the compensating winding in ___ with the armature

series

Connection to the armature of an alternator is normally done by using

sliprings

The ___ winding is made of many turns of small wire and is located at the top of the stator core

start

A synchronous motor operated with no load and used for power factor correction is sometimes called a

synchronous condenser

The differential selsyn has three stator windings connected in a wye and a rotor made of

three windings connected in a wye

The single-phase synchronous motors are based on the stator of the shaded pole motor. They operate at a speed which is synchronous with the applied frequency. These motors are also called ___ motors

hysteresis

The torque of a squirrel-cage induction motor will be maximum when the phase angle between the stator and rotor fields is

0*

The Holtz motor is a variation on the shaded pole motor. It operates at ___ RPM

1200

An induction motor rotor rotates slower than the magnetic field. How much slower is normally stated as slip speed in RPM or as percent slip? For most squirrel-cage induction motors the typical percent slip is about ___ percent

2 to 5

The Warren motor is a variation on the shaded pole motor. It operates at ___ RPM

3600

In a universal motor, inductive compensation can be used when the motor is connected to

AC only

T/F The synchronous motor is an induction motor

FALSE

The mechanical device which converts mechanical input into alternating current out is a(n)

alternator

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

bars, rings

An alternator that has a separate small alternator mounted on the shaft of its rotor is equipped with a(n)

brushless exciter

In single-phase motors such as the resistance start induction-run motor, the startwinding is disconnected by the

centrifugal switch

The universal motor has a woundarmature and brushes like an AC motor. The universal motor has an added component, the

compensating winding

In an alternator, when the rotor DC excitation current is removed there is a possibility of damaging high voltages being developed. In order to limit voltage and thereby prevent damage, a field discharge resistor or a ___ can be included in the circuit

diode

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

excitation

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

high, low

In order to increase the efficiency of the cooling, some alternators operate in an atmosphere of

hydrogen

In a universal motor, setting the brushes to the neutral plane can be done by connecting voltage to the armature, a voltmeter to the series field, and adjusting the brush position for a ___ on the voltmeter

minimum

If one phase of voltage to a three-phase motor opens, the motor may slow down, overheat, or possibly stop. This condition is known as

single phasing

The non-rotating part of an alternator is called the

stator

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

synchronous

In a motor that has a rotating magnetic field, the speed of that magnetic field is referred to as the

synchronous speed

The consequent pole motor is essentially a ___ speed motor

two

The ___ motor can operate on either AC or DC voltage

universal

Multispeed fan motors achieve multiple speeds by inserting additional ___ in series with the run winding

windings

The higher power output alternators use a

revolving field

In a universal motor, setting the brushes to the neutral plane can be done by connecting voltage to the armature, a voltmeter to the compensating winding, and adjusting the brush position for a ___ on the voltmeter

maximum

The rotating part of an alternator is called the

rotor

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

less, less

When a normal induction motor is running, the rotor does not rotate as fast as the magnetic field rotates. The rotor is being cut by the magnetic field which is inducing a voltage which is at the "rotor frequency." This frequency is __ the synchronous frequency

lower than

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 fo the new motor is a

phase rotation meter

A ___ motor operates on the principle that like magnetic poles repel

repulsion

Split-phase motors are so named because they operate on single-phase voltage, ut internally they divide the voltage in such a manner as to create a ___ magnetic field

rotating

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

The squirrel-cage rotor code letters indicate the shape (type) of rotor bars. Different types of bars have a large effect on the ___ of a motor

starting torque

In the shaded pole induction motor, the direction of rotation of the magnetic field is

toward the shading coil