DC Machines

Question 1

6 components of a dc machine

Answer 1

Armature
Pole pieces
Inter poles
Commutator
Frame
Windings

Question 2

Series field windings are wound with _____ turns of _____ wire

Answer 2

Few

Large

Question 3

Shunt field windings are wound with _____ turns of _____ wire

Answer 3

Lots of

Small

Question 4

What component of a dc generator that converts AC to DC called?

Answer 4

Commutator

Question 5

_____ operate on the principle that current flowing through a conductor produces a magnetic field around the conductor.

Answer 5

The induction of currents

Question 6

When a conductor cuts through magnetic lines of flux, a voltage is induced into the conductor. What is this principle called?

Answer 6

Magnetic Induction

Question 7

Three types of armature windings

Answer 7

Lap wound
Wave wound
Frog leg wound

Question 8

What type of armature winding provides moderate voltage and moderate current

Answer 8

Frog leg wound

Question 9

What type of wound armatures have their windings connected in parallel?

Answer 9

Lap wound

Question 10

What type of armature winding provides high voltage and low current?

Answer 10

Wave wound

Question 11

Two ways the series and shunt windings of a compound generator can be connected?

Answer 11

Long shunt

Short shunt

Question 12

The relationships of the strengths of the two fields in a compound generator determines the amount of ______ for the machine.

Answer 12

Compounding

Question 13

A generator is _____ compounded when the output voltage is the same at full load as it is at no load.

Answer 13

Flat

Question 14

When a generator is _______ compounded, it has characteristics similar to those of a shunt generator.

Answer 14

Under

Question 15

What is compounding controlled by?

Answer 15

A variable resistor in parallel with the series field

Question 16

A _________ compound generator has its fields connected in such a manner that they oppose each other in the production of magnetism.

Answer 16

Differential

Question 17

A ________ compound generator has its fields connected in such a manner that they aid each other in the production of magnetism.

Answer 17

Cumulative

Question 18

What components ride against the commutator segments and connect the armature to the external circuit of the generator?

Answer 18

Brushes

Question 19

What is the distortion of the main magnetic field of a generator called?

Answer 19

Armature reaction

Question 20

What causes armature reaction

Answer 20

Magnetic field in the current of the armature

Question 21

How is the winding of an inter pole connected in relation to the armature?

Answer 21

In series

Question 22

What are brushes made of?

Answer 22

Carbon

Question 23

What does an armature consist of?

Answer 23

Iron core
Windings
Commutator
Shaft

Question 24

Shunt windings are of _____ resistance and connected in ____ with the armature

Answer 24

High

Parallel

Question 25

What is a measure of a materials ability to become magnetized?

Answer 25

Permeability

Question 26

What is resistance to magnetism called?

Answer 26

Reluctance

Question 27

When an electromagnet reaches a point where strength increases only slightly with an increase in current, it is known as a point of ____

Answer 27

Saturation

Question 28

What is the amount of magnetism left in a material after magnetizing force has stopped called?

Answer 28

Residual magnetism

Question 29

The main magnetic field is sometimes provided by electromagnets. This is done by windings that are wound around what components of a DC machine?

Answer 29

Pole pieces/ field poles

Question 30

Another word for inter poles

Answer 30

Commutating windings

Question 31

What is the position at which the armature windings are parallel to the lines of flux and there is no induced voltage called?

Answer 31

Neutral Plane

Question 32

What are three ways that armature reaction can be corrected?

Answer 32

Rotate brushes Inter poles Compensating windings

Question 33

How is a series generator connected?

Answer 33

A1, A2 to S2, S1

Question 34

How should a shunt generator be connected?

Answer 34

F1 to A1, F2 to A2

Question 35

What would you use to clean a commutator?

Answer 35

Emory paper

Question 36

Field windings are wound into magnetic pole pieces to form ______.

Answer 36

An Electromagnet

Question 37

Series generators ____ in speed and ______ their output voltage and current as load is added.

Answer 37

Decrease speed, increase voltage and current

Question 38

Shunt generators ______ in speed and ______ their output voltage and current as load is added.

Answer 38

Increase in speed, decrease the voltage and current

Question 39

When a generator supplies current to a load, what is produced?

Answer 39

Counter EMF

Question 40

What is the measure of useful energy produced by a generator?

Answer 40

Counter torque