Alternating Current Electrical Systems

AMT 165 Aircraft Electrical Systems D-144

Which is one of the advantages of using AC electrical power in aircraft?

Greater ease in stepping voltage up or down.

How many phases of AC voltage are produced in a six pole alternator of the revolving field type for each revolution (360 degrees) of the rotor?

Three.

Which is the main advantage of the revolving field alternator?

Output voltage may be taken directly from the armature.

What are the two basic classifications of AC alternators?

Revolving field and revolving armature.

Aircraft which operate only AC alternators as a primary source of electrical power normally provide current suitable for battery charging through the use of which system?

A stepdown transformer and a rectifier.

The voltage output of an alternator may be regulated by controlling which of the following?

Amount of field current.

What monitors and regulates the output of the main generator by controlling the amount of current that flows into the exciter field?

Generator Control Unit (GCU).

Which term describes the total opposition to alternating current when the opposition consists of any combination of resistance, inductive reactance and capacitive reactance, measured in ohms?

Impedance.

Select the correct output voltage across two phases of a typical permanent magnet generator.

208 V.

Select the correct frequency for most aircraft AC circuits.

400 Hz.

How are AC alternators rated?

Kilovolt-amperes.

The output voltage of an AC alternator is regulated by controlling which of the following?

Voltage output of the DC exciter to the field coils.

Which of the following is NOT an alternator component?

Commutator.

The reverse current cutout relay disconnects the battery from the alternator when the battery voltage is greater than the alternator output.

True

Solid state voltage regulators are equipped with vibrating points and diodes.

False

When servicing AC brushless alternators, the fields must be flashed by connecting a wire from the armature to the positive lead of the battery and another from the ground terminal of the battery to the field winding.

False

A CSD (constant speed drive) is used to drive a typical AC alternator system to maintain which of the following?

Constant frequency.

A CSD (constant speed drive) unit drives its generator through the use of which of the following?

A variable hydraulic pump and hydraulic motor system.

Select the correct cooling method for a CSD (constant speed drive)-driven generator system.

Oil spray.

An IDG (integrated drive generator) combines which of the following units into one sealed housing?

Generator and CSD.

When necessary during operation, the CSD (constant speed drive) may be disconnected, shutting off the alternator by which means?

A switch in the cockpit.

Which component maintains proper output speed of the IDG (integrated drive generator)?

Governor.

How is an IDG (integrated drive generator) typically cooled?

Oil

If the IDG (integrated drive generator) scavenge oil filter were to become contaminated with slivers of metal, which maintenance should be performed?

Remove and replace the IDG.

Which types of aircraft are most likely to make use of an AC alternator system?

Transport category aircraft.