PP104, PP104

Name three basic types of DC motors:

Series motors, shunt motors, and compound motors.

Which motor has the field winding connected in parallel or in shunt with the armature winding?

Shunt motor

At position D, commutator action __________________ the current in the external circuit, and the second half cycle has the same waveform as the first half cycle.

reverses

what is used to hold the brushes firmly against the commutator?

Springs

The positive end of the shunt field winding connects to terminal _______________, and the opposite ends connects to the ________________ terminal al bush.

A

If the ends of the conductor are connected, what does it form?

A complete circuit

The rotation of generators is termed either _____________ or _________________, as viewed from the driven end.

Clockwise or counterclockwise

the armature assembly contains a laminated, soft iron core, coils and a __________, all mounted on a rotatable steel shaft.

Commutator

The _________________ windings consist of a series of coils embedded in slots in the pole faces. These coils are also connected in _______________ with the armature.

Compensating, Series

__________________ generators are usually designed to be overcompounded. This feature permits varied degrees of compounding by connecting a variable shunt across the series field.

Compound

In a shunt DC motor, since the field winding is connected directly across the power supply, the current through the field is __________________.

Constant

By reversing the direction of ___________ flow in either the armature of the field windings, the direction of a motor's rotation may be reversed.

Current

two wires carrying ____________ in the vicinity of one another exert a force on each other because of their magnetic fields.

Current

As the loop approaches the vertical position, the induced voltage ________ because both sides of the loop are approximately parallel to the lines of force and the rate of cutting is reduced.

Decreases

The negative armature lead connects to the _______________ terminal.

E

Since there is always one north pole for each south pole, there must always be an __________________ number of poles in any generator.

Even

The three types of DC motors differ largely in the method in which their __________ and ____________ coils are connected.

Field and armature

The field assembly consists of the field frame, the pole pieces, and the _______________ _____________.

Field coils

Which component of a generator completes the magnetic circuit between the poles and acts as a mechanical support for the other parts of the generator?

Frame (Yoke)

What information is stamped on the nameplate attached to the generator?

Generator rating and performance data

Which kind of armature is not widely used?

Gramme ring armature

What two functions does the frame have?

The frame has two function: It completes the magnetic circuit between the poles and acts as a mechanical support for the other parts of the generator.

Name the major parts in a practical motor:

The major parts in a practical motor are the armature assembly, the field assembly, the brush assembly, and the end frame.

What are the major parts, or assemblies, of a DC generator?

The major parts, or assemblies, of a DC generator are a field frame (or yoke), a rotating armature, and a brush assembly.

Why are the poles usually laminated?

The poles are usually laminated to reduce eddy current losses and serve the same purpose as the iron core of an electromagnet; that is, they concentrate the lines of force produced by the field coils.

Name two general kinds of armatures.

The ring and the drum

Define armature reaction.

This distortion of the magnetic field is called armature reaction.

the tendency of a force to produce rotation is called ___________.

Torque

Name two types of brushes used with a commutator:

Tube type brush, and Box type brush

When lines of magnetic force are cut by a conductor passing through them, ________ is induced in the conductor.

Voltage

When lines of magnetic force are cut by a conductor passing through them, what happens?

Voltage is induced in the conductor

what two principal parts does a direct current motor have?

a field assembly and an armature assembly.

A generator is rated in power output. The rating usually is given as the number of __________________ the generator can safely supply at its rated __________________.

amperes, voltage.

The __________ is the rotating part in which current carrying wires are acted upon by the magnetic field.

armature

The _________________ assembly of a generator consists of many armature coils wound on an iron core, a commutator and associated mechanical parts.

armature

The rotating parts of a DC generator (coil and commutator) are called an _____________________.

armature

In a series motor, the same current flowing through the field winding also flows through the ________________ ________________

armature winding.

If the current is collected by a ___________________, it is direct current, and the generator is called a DC generator?

commutator

What is located at the end of an armature and consists of wedge shaped segments of hard drawn copper?

commutator

The _____________ motor is combination of the series and shunt motor.

compound

Electrical losses are classified as _____________ losses and _____________ losses

copper, iron

The series winding may Abe either aid the shunt wind (___________ compound) or oppose the shunt winding ( ______________ compound).

cumulative compound, differential compound.

The current flowing through the armature ________ as the counter EMF increases. The faster the armature rotates, the __________ the counter EMF.

decreases, greater

In most cases, the failure of a motor to operate is caused by a defect in the _________________ electrical circuit, or by mechanical failure in the mechanism driven by the motor.

external

The brushes ride on the surface of the commutator, forming the electrical contact between the armature coils and the?

external circuit

In the shunt motor, speed is controlled by a rheostat in series with the _________________ ________________.

field windings

A blown fuse usually indicates an accidental ________ or __________ circuit.

ground or short

Electrical losses are due to the power dissipated in the form of _____________ in the resistance of the field and armature windings.

heat

Iron losses are subdivided in ______________ and eddy current losses.

hysteresis

As the number of loops is __________________, the variation between maximum and minimum values of voltage is reduced, and the output voltage of the generator approaches a steady DC value.

increase

What is the purpose of the pigtail?

is to conduct the current, rather than subjecting the brush spring to currents that would alter its spring action by overheating.

_________________ windings are used in generators that are designed for high current.

lap

Name two methods drum type armatures are constructed?

lap winding and the wave winding

The drum type advantage is that each winding completely surrounds the core so that the entire _____________ of the conductor cuts through the magnetic flux.

length of the conductor

Define flux (magnetism).

lines of magnetic flux are the same as lines of magnetic force.

The variation of DC voltage is called "ripple" and may be reduced by using more ____________, or _______________.

loops, coils

A ______________ battery usually causes the chattering of the relay switch, which controls the motor.

low

An Interpol is a pole places between the ________________ poles of a generator.

main

What is the material called that insulate the segments from the flanges and helps to prevent eddy currents?

mica

When a brush has worn to the _______________ length permissible, it must be replaced.

minimum

when ____________ current flows, no force is exerted on the wire, but when current flows through the wire, a magnetic field is set up about it.

no

A flexible, braided copper conductor, commonly called a ____________ connects each brush to the external circuit?

pigtail

A flexible, braided copper conductor, commonly called a _______________, connects each brush to the external circuit.

pigtail

What determines the output voltage of a DC generator?

product of the number of turns per loop, the total flux per pair of poles in the machine, and the speed of rotation of the armature.

what rule can be used to determine the direction a current carrying wire will move in a magnetic field?

right-hand motor rule

Counter EMF opposes the current, which causes the armature to _____________.

rotate

Name three types of DC generators:

series wound, shunt wound, and shunt series or compound wound.

There are three types of DC generators:

series wound, shunt wound, and shunt series or compound wound.

If the current is taken form the loop by _______________ _______________, it is called an AC generator, or alternator.

slip rings

what would happen if the connecting wires from the battery were permanently fastened to the terminals of the coil and there was a flow of current?

the coil would rotate only until it lined itself up with the magnetic field.

Where is the commutator located and what does it consists of?

the commutator is located at the end of an armature and consists of wedge shaped segments of hard drwn copper, insulated from each other by thin sheet of mica.

The 3 major parts, or assemblies, of a DC generator are?

the field frame (or the yoke), a rotating armature, and a brush assembly.

the amount of torque developed in a coil depends upon what factors:

the strength of the magnetic field, the number of turns in the coil, and the position of the coil in the field.

What will happen if you replace a generator with one that has the incorrect direction of rotation?

the voltage is reversed.

A motor in which speed can be controlled in called ________________ _________________ motor. it may be either a shunt or series motors.

variable speed motor

When the armature in a motor rotates in a magnetic field, a _____________ is induced in its windings.

voltage

The __________ winding is used in generators that are designed for high voltage outputs.

wave

Define commutator:

A mechanical rectifier mounted on the armature shaft of a DC generator or motor. It consists of a cylindrical arrangement of insulated copper bars connected to the armature coils. carbon brushes ride on the copper bars to carry current into or out of the commutator, providing a unidirectional current from a generator or a reversal of current in the coils of of a motor.

A practical DC generator uses __________________ instead of permanent magnets.

A practical DC generator uses electromagnets instead of permanent magnets.

If the voltage induced throughout the entire 360 degrees of rotation is plotted, this voltage is called an ______________ ________________ because of its reversal from (+) to (-) value, first in one direction and then in the other.

Alternating voltage

The positive armature lead in the generator connects to the _________ terminal.

B

On most large 24-volt generators, how are the terminals marked?

B, A, and E

Looking at position B, is the induced EMF at maximum or minimum?

In position B, the flux is now being cut at a maximum rate, which means that the induced EMF is maximum.

The strength of the induced voltage is dependent upon the speed of the conductor and the strength of the _________________.

Magnetic feild

A direct current motor is a rotating machine, which transforms direct current energy into ___________ energy.

Mechanical energy

Looking at position A, is EMF generated?

No EMF is generated, since no lines of force are cut by the coil sides

What is "high mica"?

Operation over extended periods of time often results in the mica insulation between commutator bars protruding above the surface of the bars.

In the _____________ motor, the rheostat speed control is connected either in parallel or in series with the motor field, or in parallel with the armature.

Series

________________ generators have very ______________ voltage regulation under changing load, since the greater the current through the field coils to the external circuit, the greater the induced EMF and the greater the terminal or output voltage.

Series, poor

__________ motors are often used in aircraft as engine ___________ and for raising and lowering landing gears, cowl flaps, and wing flaps.

Series, starters

The terminal voltage of a ______________ generator can be controlled by means of a ________________ inserted in series with the field windings.

Shunt generator, rheostat

Which motor is particularly suitable for use when constant speed is desired and when high starting torque is not needed?

Shunt motor

Define slip rings:

Smooth, continuous rings of brass or copper mounted on the rotor shaft of an electrical generator or alternator. current used to produce the magnetic field in the rotor of a DC alternator flows into the rotor coil through slip rings. slip rings also carry current into the deicer heating coils on an airplane propeller blade.

________________ of brushes quickly reduces the effective brush area in contact with the commutator bars.

Sparking

__________________________ is an indication of improper brush placement, which is the main cause of improper commutation.

Sparking

One method of directional reversal, called the ________________ ______________, employs a double pole, double throw switch which changes the direction of current flow in either the armature or the field.

Split field motor

The wire is always pushed away from the side where the field is _______________.

Strongest

what part is opposite of the commutator and is designed so that it can be connected to the unit to be driven?

The end Frame