AC GENERATORS Flashcards
Name 4 performance requirements for Voltage in an AC Gen
- 450 V
- Line variation less than 1 %
- Steady state voltage within 1% of 450V
- Time of recovery to within 1% of the final voltage = 1 sec
Name 3 requirements for Hz in AC Gen
- 60 Hz
- Steady state Hz variation 3.5%-4%
- Time of recovery for transients to within 1%
What is the power factor of ships?
0.8 lagging
Why is the brushless generator named that?
- No brushes
- No slip rings
- No commutators
Name 3 advantages of the brushless generator..
- Smaller
- Less maintence
- No rubbing parts
Name a disadvantage of brushless gens
Slower to respond to load changes
What to check when doing daily rounds on gens
- Heat
- Gen air temp
- No leaking of air cooler
- Noise & vibration
- No diode failure
What to check when doing Monthly rounds on gens
- VA records
- Check bearings
- Water
- Vent grills
What does AVR do?
Maintains a constant voltage to within 1% of terminal voltage
When would you need to trail a AC Gen?
- If PM or governor is changed
- If AVR or Exciter is changed
- If rotor or stator is changed
What are the requirements needed to complete AC gen trails?
- Dockside load test facility
- Laptop
- Isolated generator
- Trails form D346
In regards to AC trails what are fingerprint tests?
- Simpiler version of load trails
- Proves voltage response & recovery time
- Done after load trails
Poly phase rectification
On a rectifier what is an open circuit diode fault?
- Output V falls
- AVR compensates
- Extra strain on other diodes
Poly phase rectification
On a rectifier what is an Short circuit diode fault?
- Overload on exciter
- Damages other diodes
- Output V falls
- Supply breaker opens
What is the task of the AVR?
Keeps V output constant to within 1% of terminal V
