DC Machines Flashcards
6 components of a dc machine
Armature Pole pieces Inter poles Commutator Frame Windings
Series field windings are wound with _____ turns of _____ wire
Few
Large
Shunt field windings are wound with _____ turns of _____ wire
Lots of
Small
What component of a dc generator that converts AC to DC called?
Commutator
_____ operate on the principle that current flowing through a conductor produces a magnetic field around the conductor.
The induction of currents
When a conductor cuts through magnetic lines of flux, a voltage is induced into the conductor. What is this principle called?
Magnetic Induction
Three types of armature windings
Lap wound
Wave wound
Frog leg wound
What type of armature winding provides moderate voltage and moderate current
Frog leg wound
What type of wound armatures have their windings connected in parallel?
Lap wound
What type of armature winding provides high voltage and low current?
Wave wound
Two ways the series and shunt windings of a compound generator can be connected?
Long shunt
Short shunt
The relationships of the strengths of the two fields in a compound generator determines the amount of ______ for the machine.
Compounding
A generator is _____ compounded when the output voltage is the same at full load as it is at no load.
Flat
When a generator is _______ compounded, it has characteristics similar to those of a shunt generator.
Under
What is compounding controlled by?
A variable resistor in parallel with the series field
A _________ compound generator has its fields connected in such a manner that they oppose each other in the production of magnetism.
Differential
A ________ compound generator has its fields connected in such a manner that they aid each other in the production of magnetism.
Cumulative
What components ride against the commutator segments and connect the armature to the external circuit of the generator?
Brushes
What is the distortion of the main magnetic field of a generator called?
Armature reaction
What causes armature reaction
Magnetic field in the current of the armature
How is the winding of an inter pole connected in relation to the armature?
In series
What are brushes made of?
Carbon
What does an armature consist of?
Iron core
Windings
Commutator
Shaft
Shunt windings are of _____ resistance and connected in ____ with the armature
High
Parallel
What is a measure of a materials ability to become magnetized?
Permeability
What is resistance to magnetism called?
Reluctance
When an electromagnet reaches a point where strength increases only slightly with an increase in current, it is known as a point of ____
Saturation
What is the amount of magnetism left in a material after magnetizing force has stopped called?
Residual magnetism
The main magnetic field is sometimes provided by electromagnets. This is done by windings that are wound around what components of a DC machine?
Pole pieces/ field poles
Another word for inter poles
Commutating windings
What is the position at which the armature windings are parallel to the lines of flux and there is no induced voltage called?
Neutral Plane
What are three ways that armature reaction can be corrected?
Rotate brushes
Inter poles
Compensating windings
How is a series generator connected?
A1, A2 to S2, S1
How should a shunt generator be connected?
F1 to A1, F2 to A2
What would you use to clean a commutator?
Emory paper
Field windings are wound into magnetic pole pieces to form ______.
An Electromagnet
Series generators ____ in speed and ______ their output voltage and current as load is added.
Decrease speed, increase voltage and current
Shunt generators ______ in speed and ______ their output voltage and current as load is added.
Increase in speed, decrease the voltage and current
When a generator supplies current to a load, what is produced?
Counter EMF
What is the measure of useful energy produced by a generator?
Counter torque
