DC Generators Flashcards
(18 cards)
Given the type and application of a direct current (DC) generator, DESCRIBE the operating
characteristics of that generator including methods of voltage production, advantages of each
type, and voltage vs. load characteristics.
DEFINE terminal voltage as it applies to DC generators
the voltage that can be measured at the
output of the generator.
DEFINE counter-electromotive force (CEMF) as it applies to a DC machine
DESCRIBE the effects of commutation in a DC generator
the positioning of the DC
generator brushes so that the commutator
segments change brushes at the same time the
armature current changes direction.
More simply
stated, commutation is the mechanical conversion
from AC to DC at the brushes of a DC machine
STATE the purpose of the armature
to provide the energy conversion in a DC machine
STATE the purpose of the rotor
to provide the rotating element in a DC machine
STATE the purpose of the stator
to provide the magnetic field in a DC machine
STATE the purpose of the field
to provide a magnetic field for producing either a
voltage (in a generator) or a torque (in a motor)
LIST the three conditions necessary to induce a voltage into a conductor
A conductor, a magnetic field, and relative motion between the two.
DESCRIBE how terminal voltage of a DC generator is adjusted
Changing the magnetic field by varying the current through the field winding.
STATE the basis behind each of the four DC generator ratings
LIST the four internal losses found in a DC generator.
copper loss, eddy-current loss, hysteresis loss, mechanical loss
DESCRIBE the differences in construction between a shunt-wound and a series-wound DC generator with respect to the relationship between the field winding and the armature.
When the field winding of a generator is
connected in parallel with the generator armature,
the generator is called a shunt-wound generator
When the field winding of a DC generator is
connected in series with the armature, the
generator is called a series-wound generator
DESCRIBE the relationship between the shunt and series fields for cumulatively compounded DC generator
The two windings of the compounded generator
are made such that their magnetic fields will
either aid or oppose one another.
DESCRIBE the voltage vs. load current characteristics for a flat-compounded DC generator.
DESCRIBE the voltage vs. load current characteristics for an over-compounded DC generator
DESCRIBE the voltage vs. load current characteristics for an under-compounded DC generator
DESCRIBE the relationship between the shunt and series fields for a differentially compounded DC generator
If the two fields are wound so that their flux fields
oppose one another, the generator is said to be
differentially-compounded.
