AC Generators Flashcards
What things are required to produce an EMF by induction?
An electrical conductor
Relative movement
A magnetic field
What is the most common type of generator used today?
Brushless generator
What does the generated EMF output depend on?
The speed at which the lines of flux pass the conductor.
(Frequency)
The amount of lines of flux cutting across the conductor.
(Voltage)
What is fitted to the AC generator to make it turn?
Prime mover
Diesel engine and gas turbine unit
How is the HF Generator turned, what is its output and where is it fed to?
Belt driven
115V - 1 phase - 1600Hz
Fed to the Automatic Voltage regulator (AVR)
What sort of current is fed into the Exciter Stator?
DC
What is the purpose of the Rectifier assembly?
To convert the AC input from the Exciter Rotor into a DC output to the main AC Generator Rotor
How can the voltage generated by an AC generator be altered?
The generated voltage can only be altered by increasing or decreasing the strength of the magnetic field
If the magnetic field around the AC Generator Rotor is stable (made from a DC supply), how does the Generator produce an AC output?
As the AC Generator Rotor is turned by the Prime Mover the stable magnetic field rotates too. As this rotating magnetic field cuts through the Stator windings it produces the AC output voltage
What is the output from Generators fitted to HM Ships and how does the AVR know what’s being produced?
450V - 60Hz - 3 phase
The AVR takes a sample using a sensing line
What the difference between AC Generators and AC Motors?
Generators turn mechanical movement into electrical energy, motors turn electrical energy into mechanical movement.
What are the components of a single loop generator?
Poles Carbon brush Slip ring Load Wire loop/armature
How is current created in a single loop generator?
As the loop rotates an EMF is generated (induced in to the loop), and if it is connected to an external circuit, a current will flow around the loop and the external circuit.
What are the 6 components of the brushless generator?
Prime mover High frequency generator Automatic voltage regulator Exciter Rectifier assembly Main generator
What does the prime mover do?
The item which drives the rotor of the exciter, the generator and the HF generator.
What does the high frequency generator do?
Supplies voltage to the windings of the AC exciter via the automatic voltage regulator (AVR).
What does the automatic voltage regulator do?
Supplies a DC to the AC exciter and maintains the generator output at 450 V.
What does the AC exciter do?
The rotor of the AC exciter cuts the magnetic field of the set up by the HF generator/AVR, this gives an AC output which is fed to the rectifier assembly.
What does the rectifier assembly do?
It converts the AC excited output into DC which is then fed to the rotor of the main generator.
What does the main generator do?
The rotor of the generator sets up a rotating magnetic field which cuts across the stationary windings of the stator, this produces the final AC of 450 V, 60Hz, 3 phase output.
