IV Grammar.Skim the text to fill in the gaps with correct prepositions.

1 Most naval aircraft areusing brushless generators __voltage generation.

2 The advantage __ a brushless generator __a brush-type isits increased reliability

and greater operating time ___ overhaul.

3 It has a 12-poleac exciter and a three-phase, half-wave diode rectifierrotating __

the exciter armature and main generator field assembly.

4 The exciter rotor is a hollow frameassembly __ the main ac field mounted __ the

__ and connected __a common drive shaft.

5 A single-phasepermanent magnet generator (PMG) furnishes controlvoltage and

power __the voltage regulator.

6 Threehalf-wave rectifiers are __ the exciter rotor and connected __ the exciter

armature windings.

7 Agenerator shaft shear section prevents possible damage__ the engine or drive

unit if the generator seizes.

8 A fan__ the drive end of the generator provides coolingairflow __ the rotor.

9 The generator __ air duct adapter allows a vent tube __ be attached __ the

generator so that built-__ air and fumes created __ thespinning generator can be

vented __the outside __ theaircraft.

10 Theaircraft engine or gearbox oil enters the generator__ an inlet port and

leaves __ an exit port __the mounting flange __ the generator.

11 As the oil passes__ the generator, it absorbs the heat __ the rotorand stator.

12 __the same time, it cools the rotating seals,lubricates and cools the bearings,

and is used __ theconstant speed drive operation.

13 Theelectromagnetic field, built __the excitation currentflowing __ the exciter,

induces current flow __ therotating three-phase exciter rotor.

14 This current is half-wave rectified __ rotating rectifiers.

15 The rotating electromagnetic field induces an acvoltage __the three-phase,

WYE-connected, outputwinding __the generator stator.

16 Using anintegral ac exciter eliminates the need __brushes__ the generator,

which minimizes radio noise __other avionics equipment.

17 Two three-phase differential transformers provideprotection __ shorts __ the

feeder lines __ the generator and the bus.

18 Its coils sense the current flow __ each __the legs that connectthe ground side

__the generator stator __ ground.

19 Theother transformer is __the main bus and senses currentflow __ the three

feeder lines.

20 A short __the feederline would cause the transformers sensing a difference__

current __ trip the generator __ line.

21 It consists __ a softcopper strip embedded __ and insulated __ thegenerator

stator assembly.

22 A device, such as an aircraft engine, that providesthe driving force __a

generator, is a prime mover.

23 As power requirements grew, itbecame necessary __ furnish ac power __ a

constantfrequency, __ save weight and improve performance.

24 The constant frequency is obtained __ constant speeddrives such as

hydromechanical constant-speed drive(CSD) units.

25 It holds thefrequency steady __ within a few hertz __the desired400 Hz.

26 Air or gas turbine drives, whichget the air supply __ using bleed air __ the jet

enginecompressor or __a separate compressor, aresomewhat smoother

__operation and hold steady-statefrequencies __ within ±10 Hz.

27 The constant rpmcharacteristic __ the turboprop engine gives good frequency

stability __ the ac generator output.

28 Thepropeller mechanical governor will hold the generator frequency __400 ±4

Hz.