Generators Flashcards
The generator left-hand rule
(T)humb- direction the conductor
(I)ndex - direction of the (f)lux lines
(M)iddle- direction of induced EMF
Two instrument used to measure current
- Ammeter
2. Galvanometer
The component which converts the AC output of a simple AC generator into DC out (Not an invertor)
Commutator
The method of how a commutator maintains DC output in a basic DC generator
At any given point, the brushes only make contact with 1 side of the commutator
Although the current reverses direction in DC generator, the ________ causes current to flow in only one direction
commutator
The 4 main parts of a DC generator
- Field frame (yoke)
- Commutator
- Brushes
- Armature
The type of armature typically used in a DC generator
Drum-type
The two major components of the DC generator armature
- Iron core
2. winding
The two functions of the DC commutator split ring
- Collecting the current from the armature
2. Converting the AC current from the armature into DC output
Two typical construction materials of DC generator brushes
- carbon
2. graphite
The function of the carbon/ graphite brushes in a DC generator
To collect current from the moving commutator
The means at which the external circuit is connected to the carbon brushes
Pigtails
The 3 types of DC generators
- Series-wound
- Shunt-wound
- Compound
The DC generator with the poorest voltage regulation capabilities
Series wound
The relationship between voltage and current in a series wound DC generator
The current through the field coils increases as the load voltage increases
Typical DC generator rating
300 amps, 28 V
The function of a current limiter in a DC Generator
Limiting of the generator output current in a DC generator
The function of the Reverse-current cutout in a DC generator
The disconnection of the battery from the generator when the generator output is lower than the battery output
The reason why the reverse current cutout disconnects the battery from the generator during low generator output
If the generator output is lower than the battery output, the battery would discharge itself through the generator armature
The term for When the battery attempts to discharge itself through the generator armature and attempts to drive the generator as a motor
Motoring
The type of damage mostly found on contacts of any type
Pitting
In a DC generator, the component that is in between the carbon brushes and the external circuit
The pigtails
Brushes are held in place against the commutator via
Spring loaded brushes
When the spring tension on a DC generator is poor, the most probable damage that will occur
DC generator Arcing occurs when
The type of DC generator that a Starter Generator is
Compound
Description of current flow through a starter generator during starting and then in generator mode
Starter mode- current flows through both series and shunt windings
Generator mode- current only flows through shunt windings
If no direction of rotation is stamped on the data plate of the generator, the direction of rotation is marked by:
An arrow on the cover plate of the brush housing
The 3 components that make up a three-unit regulator in a DC generator system
- Voltage regulator
- Current limiter
- Reverse current cutout
Heavy duty DC generator systems use this type of voltage regulator
Carbon-pile voltage regulator is used in which type of system
principle of operation of resistance in a carbon pile regulator
As pressure is increased to the stacks, the resistance goes down
The two means of modulating pressure in a carbon pile for it to work
- Spring
2. Electromagnet
The function of the spring in a carbon pile
Provides the means of compressing the carbon disc/ plates in a carbon pile
The function of the electromagnet in a carbon pile
what Pulls the spring back in a carbon pile
In a carbon pile voltage regulator, the generator output is in series with
The electromagnet which is in series with the output voltage
The main benefit of a starter-Generator for an aircraft
Lesser weight than having a separator starter motor and separate generator
Description of the Hacksaw Blade test
Place armature on growler and slowly rotate the armature while holding a thin hacksaw blade slightly above the armature. If there are shorts, the hacksaw Will vibrate
Describe armature reaction
When current flows through the armature, the armatures magnetic field interferes with field between the generator poles
Armature reaction becomes greater with
Generator load increase/ current
hazard that Armature reaction can cause
Shorts between commutator and brushes
The way that generators counteract armature reaction
Inter poles
Inter-poles are wired in _______with the load on the generator
Series
The letters of the 3 terminals on a generator
A, B, E
The positive armature lead attaches to the terminal labeled ______ on a generator
B
The negative armature lead attaches to the terminal labeled ______ on a generator
E
The positive end of the shunt wingdings attaches to the terminal labeled ______ on a generator
A
