Generation Flashcards
(22 cards)
What is the primary function of a generator?
To convert mechanical energy into electrical energy through electromagnetic induction.
What fundamental principle is generator operation based on?
Michael Faraday’s 1831 discovery that a magnetic field can create current flow.
When is maximum voltage induced in a single loop of wire rotating in a magnetic field?
When the loop sides are parallel to the magnetic flux lines because the wires cut the lines at right angles.
What rule determines the direction or polarity of the induced electromotive force (EMF) in a generator?
The Left-hand rule for generators.
How is alternating current changed to direct current in a basic AC generator?
The slip rings of a basic AC generator are replaced with two half-cylinders called a single commutator.
What is ‘ripple’ in DC voltage, and how is it reduced?
Ripple is the variation in DC voltage, and it is reduced by adding more loops to the armature.
Which component of a DC generator acts as the foundation and completes the magnetic circuit, also providing mechanical support?
The field frame (yoke).
What material are commutator segments typically made of, and how are they insulated from each other?
Hard-drawn copper, insulated by mica.
What is the purpose of ‘pig-tails’ on generator brushes?
A flexible braided-copper conductor that connects each brush to the external circuit. They conduct current, eliminate current in springs, and minimize sparking.
Which type of DC generator has its field winding connected in series with the external load?
Series-wound.
Why are series-wound generators generally not suitable for aircraft applications?
Due to their poor voltage regulation.
In a shunt-wound generator, what happens to the output voltage as the load increases?
It decreases.
What is armature reaction in a DC generator?
Current flowing through the armature creates its own electromagnetic fields that distort the main magnetic flux lines between the generator poles.
How do interpoles help to counteract armature reaction?
They are special field poles placed between main poles that have the same polarity as the next main pole in the direction of rotation. They are connected in series with the load, so their magnetic strength varies with the load, effectively keeping the neutral plane in the same position.
How are generators typically rated in terms of power output?
Usually in amperes at a specified voltage (e.g., 300 amps at 28.5 volts).
For a large 24-volt DC generator, what do the ‘B’ and ‘E’ terminals typically represent?
B: Positive armature lead. E: Negative armature lead (and where load current exits).
How is the output voltage of a generator primarily controlled?
By varying the field current.
What components are included in a three-unit regulator for light aircraft?
A current limiter, a reverse current cutout, and a voltage regulator.
What is the purpose of the reverse-current cutout in a generator system?
To disconnect the battery from the generator if generator output is lower than battery output, preventing ‘motoring the generator’ (battery discharging through the generator armature).
If there is no residual voltage in a DC generator during troubleshooting, what procedure can be performed to restore magnetism?
Flashing the field, by momentarily passing current through field coils in the normal direction.
What tool is used to test an armature for open circuits and shorts?
A growler.
When resurfacing a commutator, what type of abrasive material should never be used?
Emery cloth.
