AC GENERATORS

Question 1

Name 4 performance requirements for Voltage in an AC Gen

Answer 1

1. 450 V
2. Line variation less than 1 %
3. Steady state voltage within 1% of 450V
4. Time of recovery to within 1% of the final voltage = 1 sec

Question 2

Name 3 requirements for Hz in AC Gen

Answer 2

1. 60 Hz
2. Steady state Hz variation 3.5%-4%
3. Time of recovery for transients to within 1%

Question 3

What is the power factor of ships?

Answer 3

0.8 lagging

Question 4

Why is the brushless generator named that?

Answer 4

• No brushes
• No slip rings
• No commutators

Question 5

Name 3 advantages of the brushless generator..

Answer 5

1. Smaller
2. Less maintence
3. No rubbing parts

Question 6

Name a disadvantage of brushless gens

Answer 6

Slower to respond to load changes

Question 7

What to check when doing daily rounds on gens

Answer 7

• Heat
• Gen air temp
• No leaking of air cooler
• Noise & vibration
• No diode failure

Question 8

What to check when doing Monthly rounds on gens

Answer 8

• VA records
• Check bearings
• Water
• Vent grills

Question 9

What does AVR do?

Answer 9

Maintains a constant voltage to within 1% of terminal voltage

Question 10

When would you need to trail a AC Gen?

Answer 10

• If PM or governor is changed
• If AVR or Exciter is changed
• If rotor or stator is changed

Question 11

What are the requirements needed to complete AC gen trails?

Answer 11

• Dockside load test facility
• Laptop
• Isolated generator
• Trails form D346

Question 12

In regards to AC trails what are fingerprint tests?

Answer 12

• Simpiler version of load trails
• Proves voltage response & recovery time
• Done after load trails

Question 13

Poly phase rectification

On a rectifier what is an open circuit diode fault?

Answer 13

• Output V falls
• AVR compensates
• Extra strain on other diodes

Question 14

Poly phase rectification

On a rectifier what is an Short circuit diode fault?

Answer 14

• Overload on exciter
• Damages other diodes
• Output V falls
• Supply breaker opens

Question 15

What is the task of the AVR?

Answer 15

Keeps V output constant to within 1% of terminal V

Question 16

What does the MK17 filter unit do?

Answer 16

Improves HF 160 hz supply

Question 17

What does the MK41 Monitoring unit do?

Answer 17

Ensures parameters are in tolerance

Question 18

What does the MK1 (PU) Protection unit do?

Answer 18

Provides the shut down ability

Question 19

What does the MK1 (CN) compensation unit do?

Answer 19

Compares actual volts to desired volts

Question 20

What does the MK 169p Output control amplifier do?

Answer 20

Has 4 MOSFETS

Question 21

Name 4 tests done during a load trail

Answer 21

1. Heat run
2. Speed control
3. Insulation res Hot & cold
4. Volt control

Question 22

How is the generator output frequency controlled?

Answer 22

By controlling the speed of the prime mover