Electrical SP3 Flashcards
Why is DC unsatisfactory for SMs main distribution system?
- The battery’s disadvantages are its weight (500kg per cell) and its limited capacity which, under emergency conditions, is measured in hours rather than days.
- DC machines are much larger and much heavier than their AC counterparts
- Dc generators are limited in power by ‘commutation’ difficulties which can produce defects and therefore attract more maintenance
Name typical 115V Essential loads
A: Lighting
B: Tank contents
C: Anti-condensation heaters
Name typical 115V Non-Essential loads
A: Equipment sockets
B: Domestic equipment
Name 5 power sources available to a V-Boat
A: 265DC (nominal) main battery, 17600 Ah @ 5-hour rate
B: Two 3MW turbo-generators
C: One 850kW AC diesel generator
D: One 750kW DC diesel generator
E: AC shore supplies, comprising eight 400A AC rated cables, 4 aft and 4 fwd, split port and starboard
*How do we protect against the main types of damage?
Mechanical- Strict restrictions on warm up and cool down rates
Chemical- Strict chemical limits with constant monitoring to allow corrective action if necessary
Thermal- Heat constantly removed, again constantly monitored to be shutdown if necessary
What are the different colours on the MSC BITE monitoring system?
What do they mean?
Green- within correct tolerance
Amber- warning of a fault that may lead to a trip
Red- an out of tolerance reading and trip
Blue- mode indication
Describe the AC and DC parts on MG and what controls them
- The AC machine is an 8-pole brushless machine which incorporated PMG and an exciter on the main shaft. This is controlled by MK 204 CP.
- The DC is a compound wound DC motor/ generator. This is controlled by MK 84 AVFR.
The battery must always be available as the reserve source of power, briefly tabulate the process required to carry out a CD.
A- The battery is put through a charging cycle and the purposely discharged in a controlled manner to a low state of charge. To complete the process, it is then recharged to full capacity. This improves its condition and provides a capacity check.
Name the occasions in when welding, burning or grinding must be stooped
A- The battery is above gassing voltage (288V)
B- Battery temperature exceeds 46c
C- Less than 1 hour has elapsed since completion of charge
D- H2 contents meters indicate a H2 concentration of 2% (EOOW to be informed whenever concentration reaches 1.5%)
E- Loss/reduction in airflow, or equipment failure ie LP blowers (VS yellow), whilst charging.
What are the pre requisites for a battery charge alongside?
- Ventilation system line up check
- Battery air flow> 0.63m3/sec to 0.72m3/sec (SM specific)
- Hydrogen contents measuring system in operation, indicating <1%
- DC System clear of earths
- Electrolyte agitation system running
- Pilot cell readings taken and recorded (SG and temperature
- Battery sump checked dry
- At least one CO & H2 burners running in Vent State Green
- Hydrogen clearance fans OFF
- EOOD/OOD Permission
5 tripping conditions for the DG DC Bkr
A- IPBS OFF/Reset switch B- Breaker manual push to trip switch C- Low voltage D- Overcurrent E- Reverse current F- Speed below 200rpm
5 tripping conditions for DG AC Bkr
A- IPBS OFF/Reset Switch B- Breaker manual push to trip switch C- Low voltage D- Overcurrent E- Generator Fault F- Reverse power G- DG excitation OFF/ON Switch
Briefly explain what the AC and DC diesels are, ratings, type etc
AC generator consists of a brushless rotating field altinator, rate 850kw
DC diesel generators is comprised of a shunt wound, 8 pole self exciting type and is coupled to and driven by a paxman valenta diesel engine which spins at 1200rpm
How many cables are used for SS
DC system uses 4 cables
AC system uses 8 cables
When would you connect DCSS?
- Whenever the reactor is shutdown and diesel generator unavailable the DC shore supply cables must be connected and deenergised and the links out.
- DC shore supply should only be used in long term failure of AC shore supply and the diesel generator is unavailable or when laying off main batteries.
