Power Generation Flashcards
Aircraft Batteries and Power Generation
In aviation what types of batteries are mostly used?
Lead-Acid
Nickle-Cadmium
Where is the type of battery to be used with the aircraft found?
TCDS
Is changing the type of battery in an aircraft a major alteration?
Yes
What is amp-hour?
As it sounds, producing 1 amp for 1 hour
What is an open circuit voltage?
Voltage measured when there is no load applied to the battery?
What is closed circuit voltage?
Voltage measured while a load is applied to the battery?
What is internal resistance?
The resistance present inside a battery while connected to a load
IR=OCV-CCV/I
How does constant-voltage charging work?
As the battery is charging the battery voltage is rising and the current drops off. This is also the way mos in service batteries are charged
How does constant-current charging work?
Charger varies the voltage to supply a constant current to the battery. The state of charge of the battery must be know or overcharging is likely. Used with Ni-cad batteries.
How do you neutralize the acidic electrolyte in a lead acid battery?
A solution of baking soda and water is used
How do you neutralize the basic electrolyte in a Ni-Cad battery?
A solution of boric acid and water
Which lead do you connect first on a battery?
The red or positive, then the black or negative
SLA
Sealed Lead Acid
VRLA
Valve Regulated Lead Acid
RG
Recombinant Gas
AGM
Absorbed Glass Mat
Gel Cell
Electrolyte mixed with silica
What is thermal runaway?
The low resistance of Ni-Cads allows high current flows. These high current flows raise temperatures, especially in the cells in the center, and this has the effect of lowering the resistance even more. This creates a cycle that could have on cell destroy itself and heat up cells around it contribution to other runaways
What is cell memory?
A cell that is repeatedly subjected to shallow discharge and recharge will eventually lose some of its capacity and not except a full charge
What is Faraday’s Law?
Relative motion between a wire and a magnetic field generates an electromotive force and a flow of current in a closed circuit.
Power Generation and Transformation
Generator-Magnet is stationary
Alternator-Magnet is moving
Transformer-Inductor
How is AC transformed?
Inductors
How is the voltage found in transformers?
Voltage is directly proportional to the number of turns
How is the current found in a transformer?
inversely proportional to the number of turns
How is the output of a electromagnetic power generation found?
The strength of the magnetic field
The number of conductors
The speed that the magnetic field is crossed
What is pulsating DC
DC whose voltage periodically changes, but whose electrons always flow in the same direction.
How does a shunt wound generator work?
The generator has the field in parallel to the armature.
What is residual magnetism?
The magnetism that remains in the field frame of a generator when no current is flowing in the field coils
What is residual voltage?
The voltage produced in a generator armature when the armature is rotated in the residual magnetism
What is a carbon stack?
A kind of variable resistor. The stack is pressed together it has less resistance. The voltage coil creates a magnetic field that changes the pressure on the stack
What is a voltage regulator?
A normally closed switch that is opened whenever there is voltage greater than desired in a parallel circuit. This limits the current going to the magnetic field
What is a current limiter?
A normally close switch that is opened whenever there is a current greater than desired in a series circuit. This limits the current going to the magnetic field
What is a reverse current relay?
A normally open switch which is held closed by a magnetic coil whenever there is sufficient output from the generator going through a parallel and a series circuit
What are the three ways to create relative motion?
The magnetic field remains stationary and the conductor moves through it
The conductor remains stationary, and the magnetic field moves across it
The conductor and the magnetic field remain stationary and the strength of the magnetic field changes
What is a commutator?
A mechanical rectifier mounted on the armature of a DC generator. Carbon brushes riding on the commutator carry current in and out
What are series wound generator not practical?
They can’t be controlled
What is a shunt wound generator?
The field is parallel to the generator
How does a shunt field generator work?
By controlling the amount of current that goes through the field the output of the generator can be controlled
Compound wound generator
Can be controlled adequately, and they can make more power than shunt wound. They are normally starter-generators
What provides power in an alternator?
Brushes and slip rings
What determines the frequency in a generator?
The speed at which the generator turns
What is a CSD?
A constant speed drive that will cause the generator to turn and a certain speed. It is a variable displacement hydraulic pump driving a hydraulic motor
What is CEMF?
Counter Electromotive Force is a back voltage created by moving the windings of the motor through the magnetic field
Shunt wound motors
Produce a small amount of torque but have a constant operating speed
Direction of rotation can be controlled by direction of current flow in the field or the armature
Series wound DC motors
Produce a large amount of torque initially.
As Speed increases, CEMF increases, torque drops off
Need a load
Direction of rotation controlled by direction of current flow in the field or the armature
What type of motors are AC motors?
Induction motors. The current in the armature is induced from the field.
