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
What does the MK17 filter unit do?
Improves HF 160 hz supply
What does the MK41 Monitoring unit do?
Ensures parameters are in tolerance
What does the MK1 (PU) Protection unit do?
Provides the shut down ability
What does the MK1 (CN) compensation unit do?
Compares actual volts to desired volts
What does the MK 169p Output control amplifier do?
Has 4 MOSFETS
Name 4 tests done during a load trail
- Heat run
- Speed control
- Insulation res Hot & cold
- Volt control
How is the generator output frequency controlled?
By controlling the speed of the prime mover
