The power in an AC current in which there is an imbalance of inductance and capacitance Unity Less than 100% More than 100%.
Impedance is Inductive reactance only The sum of inductive and capacitive reactance Total resistance in an AC circuit.
In a three phase AC circuit with a star connection Line voltage is less than phase voltage Line voltage is the same as phase voltage Line voltage exceeds phase voltage.
When a AC circuit is not purely resistive, and contains some reactance Effective power is equal to apparent power Effective power is greater than apparent power The power factor is less than 100%.
In a three phase AC system with star connection, phase voltage is measured between Between phase and neutral Across all three phases Between any two phases.
AC rms value is equivalent to The value of inverted DC that will provide the same heating effect The value of actual peak AC when the power factor is 100% The value of DC that would provide the same heating effect.
If a single phase voltage of a three-phase star connected circuit is 100 volts, the two phase voltage is 300 volts 200 volts 173 volts.
In a typical aircraft AC electrical system, phase voltage is 400 volts 173 volts 115 volts.
Transformers are used in AC systems to Control alternator output Convert AC to DC Step up and step down supply voltages.
A transformer used to increase the value of the supply voltage has More turns in the primary winding than in the secondary winding Fewer turns in the primary winding than in the secondary winding The same number of turns in both windings, but with thicker turns in the secondary winding.
In an aircraft system which is mainly DC, any AC requirement is supplied by Transformer rectifiers Rectifiers Inverters.
Rectification of alternating current is provided by A diode A load resistor A capacitor.
In a half wave rectifier, for each full cycle of input power A full cycle of power is produced across the load resistor A half cycle of power is produced across the load resistor A half cycle of power is produced at the diode
.
The reduction of a 28 volt supply from a 115 volts supply is achieved by A transformer A rectifier An inverter.
A transformer that halves the supply voltage will have Half as many turns in a secondary winding as in a primary winding Four times as many turns in the primary winding as in the secondary winding Four times as many turns in the secondary winding as in the primary winding.
The purpose of TRU is To control the output of an AC alternator To convert AC at one voltage into DC at a different voltage To ensure accurate load sharing in multi-generator systems.
A DC supply of 28 volts may be obtained from an AC supply of 115 volts by use of
A transformer and rectifier in one unit A transformer and inverter in one unit A rectifier and an exciter in one unit.
The function of an inverter is to Convert AC at one voltage into AC at another voltage Convert AC at one frequency into AC at another frequency Convert DC at one voltage into AC at another voltage.
The file windings of a brushless generator are Wound round a permanent magnet Supplied by a rectifier and slip rings Wound round a rotor.
The line voltage of a three-phase star connected AC generator is Less than phase voltage Equal to phase voltage Greater than phase voltage.
A frequency wild generator is An output of control alternator A constant frequency generator A generator producing variable frequencies proportional to engine speed.
AC generators are rated in KW KVA KVAR.
In a constant speed generator, frequency depends on Engine speed CSD speed Stator speed.
The output from an AC generator is taken from The rotor via slip rings The stator The brushless rotor.
Alternator normally have rotating fields and stationary armatures in order to Reduce the weight of the unit Reduce the size of the unit Regulate the output current.
If over control of the CSDU is lost It will overspeed resulting in mechanical damage It will be automatically disconnected It may be manually disconnected.
The normal supply frequency from a constant speed AC alternator is 115 hertz 200 hertz 400 hertz.
If a CSDU is disconnected in flight It is automatically reconnected when the engine is shut down It cannot be reconnected when the aircraft is on the ground It may be reconnected at any time by a manually activated electro –magnetic clutch.
In a constant frequency generator, voltage output is increased by Increasing the rotor RPM Increasing the generator field current Disconnecting the constant speed unit.
Alternators used in aircraft systems are normally Two phase, with single-phase voltage of 200 volts Three phase, with single-phase voltage of 115 volts Single phase, with voltage 28 volts.
The frequency of an AC generator supply is a function of The number of poles and generator speed The number of poles and field circuit current The generator speed and field circuit current.
The output of the full wave bridge rectifier in a constant frequency AC generator is Direct current for the excitation of the main generator Alternating current for the excitation of the exciter generator Direct current for the excitation of the exciter generator.
In a brush less AC generator, the magnetic filed required at engine start is supplied by A DC from aircraft’s battery Rectified AC from the battery Permanent magnets.
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