Midterm Flashcards
Label current flow diagram #1
Series field windings
Label current flow diagram#2
Shunt field windings
Label current flow diagram #3
Brushes
Label current flow diagram #4
Commutator
Label current flow diagram #5
Inter poles
Label current flow diagram #6
Commutating winding
Label current flow diagram #7
Compensating windings
Label current flow diagram #8
Main pole
Label current flow diagram #9
Shaft
Label current flow diagram #10
Armature
Left hand generator rule what do each finger represent
Thumb: direction of force
Middle: direction of current
Index: magnetic field (pointing south) think knuckle of index as North Pole
Shunt diagram which ones a long shunt which ones a short?
1: Short shunt is the one that encases just the motor
2: Long shunt goes from one end of the cct to the other
what’re the 4 main magnetic components of a dc machine
Main poles
Inter poles
Armature winding
Field winding
The relationship of the series and shunt fields in a compound generator determines the amount of_____________ for the machine
Stable output voltage
When a generator is _______ compounded, it has characteristics similar to a shunt generator
Options:
A: flat
B: Over
C: Under
D: Not
C: Under compounded
A generator is _______ compounded when the output voltage is the same at full load as it is at no load
Options:
A: Over
B: Under
C: Flat
D: not
C: flat
Is the resistance of a shunt winding higher or lower than the resistance of the series field winding?
Shunt—-> smaller wire, higher resistance
What are the windings around the inter poles called
Commutating windings
What type of machine converts electrical input to mechanical output
Motor
What type of wound armatures have their wires connected in series?
Options:
A: Lap
B: Wave
C: Frog leg
B: Wave
What type of armature winding provides low and high current
Options:
A: Lap
B: Wave
C: Frog leg
A: lap
What component of a dc generator converts ac to dc
options:
A: armature
B: brushes
C: main poles
D: commutator
D: commutator
What 2 sources of magnetic flux interact to cause armature reaction
Current in field windings, current in armature windings
In a series motor are torque and speed inversely or directly proportional
Inversely
Shunt field windings are wound with _______ turns of _______ wire relative to series field windings
Options
Block one:
A: many
B: less
Block two:
A: larger
B: smaller
Many smaller
Series field windings are wound with ________ turns of ________ wire relative to shunt field windings
Options:
Block one :
A: Less
B: many
Block two:
A: larger
B: smaller
less larger
Does the armature winding carry the same current as the shunt field winding
No
Once a dc motor is started and all the resistance is removed what limits the current through the armature?
Counter EMF
What is the mechanical force used to turn a generator called
Prime mover
What is an advantage of a separately excited dc machine
Better control of output voltage and speed
In reference to the left hand rule for electro magnets what do the fingers and thumb represent
Thumb; North Pole
Fingers: direction of current flow
Is armature current proportional to armature reaction?
Yes
What type of compound generator has its shunt field windings connected in parallel with both the armature AND series field windings
Long shunt
With a constant load can armature reaction be corrected by shifting the brushes and therefore adjusting the neutral plane setting
Yes
What’re the four types of enclosures for dc machines
Open
Weather
Drip
totally enclosed
Is the commutator an electrical or mechanical switch
Mechanical
What type of dc motor is used when constant or adjustable speed is extremely important
Options:
A: shunt motor
B: generator
C: series motor
A: shunt motor
What’re the 3 types of dc machine field windings
Series, shunt, compound
What’re the 3 types of dc machine field structures?
Permanent magnet, separately excited, self excited
What are the series field windings connected in series with
Options:
A: shunt
B: brushes
C: commutator
D: armature
D: Armature
What is the purpose of the pole pieces in a dc machine
Options:
A: create a whole neutral plane
B: create magnetic flux
C: add resistance to limit current
D: increase Lorentz force
B: create magnetic flux
3 factors that determine output of a generator
pick 3
Magnetic field strength
Armature surface area
Rotational speed of the Commutator
Speed armature is driven
Brush spacing
# of conductors in armature
Magnetic field strength
# of conductors in armature
Speed armature is driven by
Is the voltage induced into the armature windings of a dc generator ac or dc?
AC
What causes the shift of the neutral plane on a dc motor under load
Options:
A: magnetic field
B: angle of which the field windings are wound
C: armature vibrations
A: magnetic field
What’re the 3 different compound generators called
Over, flat, and under compounded
What is resistance to magnetism called
Options
A: Permiability
B: reluctance
C: saturation
B: Reluctance
Where are the magnetic flux lines most densely concentrated
Poles
Which way does current flow in electron flow theory?
NEG to POS
Or
POS to NEG
NEG to POS
When an electromagnet reaches where strength increases slightly with an increase of current
This is known as?
Options
A: permeability
B: reluctance
C: saturation
C: saturation
What are two types of magnets
Permanent, electro magnets
What component of a dc machine supports the shaft and allows it to rotate freely
Options:
A: commutator
B: brushes
C: bearings
D: armature
C: bearings
What’re the brushes made of in a dc machine
Options:
A: iron
B: lead
C: magnesium and carbon
D: carbon graphite
D: carbon graphite
Label realistic motor #1
End plate
Label realistic motor #2
Terminal block
Label realistic motor #3
Commutator
Label realistic motor #4
Armature winding
Label realistic motor #5
Iron core
Label realistic motor #6
Main poles
Label realistic motor #7
Field windings
Label realistic motor #8
Bearing
Label realistic motor #9
Shaft
Label realistic motor #10
Cooling fan
Label realistic motor #11
Enclosure
Label realistic motor #12
Base
Label realistic motor #13
Carbon graphite brushes
