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.
3 differences between AC and DC Bkr
- Closing coil supply is taken directly from DC busbar and a DC-DC converter provides 50v+ for the retaining circuit and CCCC
- The buffer amplifier monitors the DC voltage and converts it to AC output for use in overcurrent module.
- The centre main isolating contact is not used as the supply requires on 2 connections
Two types of ACB
IFR6
IFR3
IF6
List supplies or converted supplies found onboard
450 60hz
265v
115v
160v DC
List 4 typical 115 ESS or NON ESS loads
Most common is LIGHTING, others:
- Salinometers
- Navigation equipment
- Anticondensation heaters
- Tank contents
- Radar/radio domestic equipment
- Equipment sockets
What audible alarms do we have that require immediate attention?
- Master flashing alarm
- Fire alarms
- Flood alarms
- Group warning system
Procedure for 440v earth checks
-Select the Port/Off/Stbd switch to the side required
-Position the required switch to CAL
-Depress read indicator button and check indication on ohmmeter is within red sector, if not investigate
- Select the service to be earth checked on the port select or stbd select switch as required
- Depress the read indicator and check the resistance to earth indicator on the ohmmeter. Readings of less than previous or expected levels are to be investigated.
If an earth fault is detected inform EOOW/EOOD immediatley
Methods of propulsion, where are they controlled/
Electrical propulsion motor
Secondary propulsion motor
Controlled from hydraulic manifold in the Engine Room and Remotely from the ESP in the Manoeuvring Room
What are the different types of compartment lighting and their supplies?
Primary source is 115V 60hz fluorescent bulb supplied from the essential busbars via transformers.
Secondary source 265V DC incandescent lighting supplied from the battery side of the battery breakers.
Emergency source is the automatic emergency lantern supplied via own built in power source chargeable batteries.
