Mod 6 Unit 2 ALTERNATORS
According to the electron theory of the flow of electricity, when a properly functioning DC alternator and voltage regulating system is charging an aircraft battery, the direction of current flow through the battery:
is into the negative terminal and out of the positive terminal.
The part of the DC alternator power system that prevents reverse flow of current from the battery to the alternator is the:
rectifier.
Capacitors are sometimes used in DC circuits to:
smooth out slight pulsations in current/ voltage.
Typical application for a zener diode is as:
voltage regulators.
How would you connect a three phase alternator to the external (load) circuit for current advantage?
"Delta" connected.
How would you connect a three phase alternator to the external (load) circuit for voltage advantage?
"Wye" connected.
What would be the output voltage of an alternator with the alternator switch and circuit breaker on, if the engine has been hand propped to start because the battery was removed?
0 (zero) volts.
What would be the output voltage of a 14 volt alternator having an open field circuit?
0 volts.
How many electrical degrees apart are the three stator windings of the 14/28 volt alternator?
120 degrees.
The maximum allowable voltage drop between the generator and the bus bar is:
2 percent of the regulated voltage.
A negative diode is identified by what markings?
Black or green dot or part number
Which of the following would be considered an advantage of a 14 volt alternator?
Both answers are correct.
How is the output voltage of a DC alternator controlled?
By controlling field current through the rotor.
How is a 14 volt alternator field excited?
By passing direct current through the rotor assembly.
The purpose of a rectifier in an electrical system is to change:
Alternating current into direct current.
The difference between a 14 volt DC generator and a 14 Volt alternator is:
Alternator has a rotating field, the generator has a stationary field.
One of the advantages of an alternator over a generator system is.
Alternator has a stationary armature.
The process of increasing and decreasing field current is performed by:
An ACU (Alternator Control Unit).
Where is the voltage generated in an alternator?
In the stator.
Which of the following is a correct test procedure if a 14 volt alternator has zero voltage output?
Jump battery positive (+) terminal to "F" terminal.
What would be the result if a 14 volt alternator's direction of rotation was reversed?
Normal operation with a possible loss of cooling.
When troubleshooting an alternator that is not working, Voltage is found at terminals 2 and 3 but NOT at F on the vibrating alternator control unit. What is the most likely cause?
Open in the field relay coil.
What function other than rectification does the six diodes perform for the alternator system?
Prevent the battery from discharging through the stator windings.
What is one of the functions of the field relay in an alternator system?
Prevents battery current from flowing in the field circuit when the system is secured.
The alternator rectifier unit performs which of the following functions?
Prevents reverse current through the stator.
A positive diode is identified by what markings?
Red dot or part number.
What type of bearings are used in the 14 volt alternator slip ring end housing?
Roller (needle).
What type of bearing is used in the 14 volt alternator drive end frame?
Sealed ball.
What is the purpose of the capacitor on terminal #4 of the vibrating point type alternator control unit used for the 14 volt alternator?
Smooths out output voltage.
The alternating current produced in the stator of a 14V alternator, is changed to DC by the use of what?
Solid state full wave rectifier unit.
The 14 volt alternator VR works on what principle.
Spring tension versus electromagnetic force.
What may be the cause of damage to the diodes.
The battery leads were connected backwards
Why are the brushes of a DC alternator more efficient and have a longer service life than those of a DC generator
The brushes pass only field current.
What would be the result in a 14 volt alternator system if the battery leads are connected with reverse polarity?
The diodes would probably be damaged.
The stator of an alternator is excited by what?
The field assembly.
What prevents voltage from dropping to zero when the lower VR points are open?
The field resistor.
Why is an RCCR not required in a 14 volt alternator system?
The output is rectified by diodes which also prevent reverse current.
The field induces voltage into what part of an alternator?
The stator assembly.
Which of the following is regulated in a generator to control its voltage output?
The strength of the field.
High voltage at high RPM may be the result of which of the following?
The upper points of the VR are open to ground.
Which of the following prevents overcharging the battery in a 14 volt alternator system?
The voltage regulator.
What is the purpose of the rotor in a 28 volt alternator?
To induce AC into the stator.
What is the purpose of the rotor in a 14 volt alternator?
To produce a DC magnetic field to induce an ac voltage in the three phase stator.
What is the purpose of the slip rings?
Transfer DC current to the rotor.
What type of current is found in the vibrating points of an alternator voltage regulator that uses transistors for voltage control.
Transistor base current.
The field gets its current through the field resistor:
When the 14 volt alternator voltage regulator points are open.
If the upper points of the VR on the 14 volt vibrating regulator are stuck to the stationary center point, what will be the effect on voltage output?
Zero voltage.
The generating system of an aircraft charges the battery by using:
constant voltage and varying current.
The solid state full wave rectifier unit used in the alternator system performs what function?
Changes the alternating current produced in the stator of a 14V alternator to DC.
The diodes as used in the alternator system takes the place of what component in the generator system?
Commutator and brushes.
Which of the following is NOT a use for diodes in an electrical circuit.
Current limiters.
