AC

Question 1

AC SYSTEM ON AN AIRCRAFT

Answer 1

115V - 400Hz - 3 separate phases

Question 2

AC has extra resistance but it’s known as

Answer 2

Reactance measured in ohms

Question 3

If the Hz drops then

Answer 3

The resistance drops

Question 4

On the aircraft to ensure we have constant frequency we have

Answer 4

Generator RPM - controlled by the CSU

Question 5

Voltage is determined by

Answer 5

Voltage regulator

Question 6

Split Bus system

Answer 6

No two AC sources are on the same bus bar

Question 7

PARALLEL BUS SYSTEM

Answer 7

Normally all generators are on all busbars

Question 8

When a fault is sensed

Answer 8

The GCU automatically opens the GCB

Question 9

GCU protects

Answer 9

Ac generator over and under voltage
Excess current
Under frequency
Over frequency
Internal short

Question 10

When operating the fire handle

Answer 10

We never touch the bus tie breaker

Question 11

To ensure generators are sharing the same load

Answer 11

They must have the same voltage and frequency and current - test by using a current transformer

Question 12

Correct Real load shedding - parallel systems

Answer 12

Make sure the torque is the same

Question 13

Correct reactive load shedding - parallel systems

Answer 13

We must make sure the voltage is the same

Question 14

AC in aircraft

Answer 14

400Hz

Question 15

Frequency formula

Answer 15

Number of poles /2 * RPM/60seconds

Question 16

If there’s a difference between generator output current and bus bar input current

Answer 16

There is a differential fault

Question 17

When the engine fire shut off handle is pulled then

Answer 17

The exicter control relay and generator breaker open

Question 18

hot buses and direct bus bars

Answer 18

Directly connected to the battery

Question 19

Capatance

Answer 19

Is the ability of the circuit to hold charge

Question 20

Starter generator is used to

Answer 20

Start the core engine until reaching self sustaining speed

Question 21

Rotating armature ac generators

Answer 21

Rotating coils are heavy
Coils are difficult to cool
Resistance across the brushes to the slip ring is high

Question 22

Stationary armature generators (AC)

Answer 22

Stator windings are connected in series
Max output depends the amount of heat that can be absorbed by armature
Rated in Va or kVa

Question 23

AC generator have ___ phases usually

Answer 23

3 (3 stator armatures)

Question 24

3 phase spacings are x degrees

Answer 24

120

Question 25

3 phase system advantages

Answer 25

Simple and efficient
Easier to connect in parallel
Greater power to weight ratio

Question 26

2 phase ac generator is known as

Answer 26

Line voltage

Question 27

Brushed ac generator

Answer 27

Initial excitation current is supplied by the battery

Question 28

Brushless generator has

Answer 28

A main generator and an exciter generator on the same shaft

Question 29

CSD keeps

Answer 29

Generator speed constant regardless of engine speed

Question 30

If CSU displays

Answer 30

High temp and low oil then it should be disconnected

Question 31

If a bus bar short circuits

Answer 31

It’s isolated and consumers are lost

Question 32

Isolation of a bus bar

Answer 32

Decreases its consumption