Generators & Power Management — Most Asked Questions
17 questions asked about generators & power management across the General and Fn 5 and Fn 3 papers, heaviest first.
Learn the system first
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1 Emg generator regulation
Also asked: “Emg gen regulation”
Answer
The emergency generator must start itself and take load in 45 seconds from its own space above the uppermost deck.
- Voltage or frequency collapse trips the bus-tie breaker and sends the auto-start signal.
- Within 45 seconds the set starts, builds voltage and takes the emergency board; batteries carry lights and alarms meanwhile.
- Location is above the uppermost continuous deck, outside the engine room, with independent fuel and starting.
- If it fails to come on load, batteries hold selected lights, comms and alarms for at least half an hour.
Surveyor follow-up: the set starts but the board stays dead — bus-tie, breaker or AVR, and where do you look first?
Full theory: Emergency Generator: Testing & Requirements -
2 How to increase and reduce load on generator
Also asked: “How generator trips after load increased”, “How to increase load manually on generator?”, “How do you change load in Generator”
Answer
Active load follows fuel, reactive load follows excitation: governor for kilowatts, AVR for volts and power factor.
- Raise the governor setting to take more kilowatts; the set speeds up, takes load and slows its partners down.
- Lower the governor to shed load; with equal droop characteristics machines share in proportion to capacity.
- Trim excitation for reactive sharing: more field raises generated voltage and takes more of the lagging load.
- Watch frequency and current together — hunting means governors fighting, dark lamps mean a syncing error.
Surveyor follow-up: one set takes all the load after paralleling — governor or excitation, and which handle do you touch?
Full theory: Diesel Generator Starting Procedure & Alternator On-Load | Marine Guide -
3 Type of governor
Also asked: “Type of governor ....governor maker”
Answer
Governors are mechanical, hydraulic or electronic — all trading speed error for fuel, with droop or isochronous behaviour.
- Mechanical: flyweights against speeder springs move the fuel rack directly, simple and rugged.
- Hydraulic: pilot valve and power piston amplify the flyweight signal for big engines needing real force.
- Electronic: speed sensor, controller and actuator hold tightest control with load sharing logic.
- Droop lets speed fall slightly with load for stable sharing; isochronous holds speed flat with reset action.
Surveyor follow-up: two sets hunt against each other at steady load — droop matched or fighting, and what do you adjust?
Full theory: Governing and Speed Control — Droop, Load Sharing and the Overspeed Trip -
4 Generator not developing voltage reasons
Also asked: “Genrator not generating voltage reason”, “If generator not producing voltage . then wt are reasons”, “Generator voltage not coming reason”
Answer
No volts means no excitation path: dead residual magnetism, failed diodes, worn brushes, faulty AVR or an open field.
- Lost residual magnetism after long standstill — flash the field to rebuild it.
- Failed rotating diodes, worn slip rings and brushes, or an open lead in the excitation circuit.
- Faulty AVR or lost excitation supply starving the main field.
- Low-but-present volts splits further: slow prime mover, wide air gap, shorted field coil, weak poles or misconnected stator coils after repair.
Surveyor follow-up: exciter gives full volts but the main field takes no current — open or short, and where do you megger first?
Full theory: Diesel Generator Starting Procedure & Alternator On-Load | Marine Guide -
5 How to parallel generator
Also asked: “How to take parallel generator”, “How to parallel 2 generators with diag”
Answer
Parallel on matched volts, frequency and phase: sync check, lamps dark, breaker shut, load shared by governor.
- Incoming set to rated voltage and slightly fast frequency with phase sequence proved.
- Lamps-dark or synchroscope method: close the breaker as the pointer crosses twelve with lamps dark.
- Wrong closing motorizes the slow set and can trip the board — check speed before reaching for the handle.
- After closing share kilowatts on governors and reactive load on excitation, watching frequency hold.
Surveyor follow-up: lamps bright at the close attempt — shut or wait, and what happens if you shut now?
Full theory: Diesel Generator Starting Procedure & Alternator On-Load | Marine Guide -
6 Parlleling of generator
Also asked: “Paralleing of generator”, “Paralling of generator”
Answer
Parallel on matched volts, frequency and phase: sync check, lamps dark, breaker shut, load shared by governor.
- Incoming set to rated voltage and slightly fast frequency with phase sequence proved.
- Lamps-dark or synchroscope method: close as the pointer crosses twelve with lamps dark.
- Wrong closing motorizes the slow set and can trip the board — check speed before the handle.
- After closing share kilowatts on governors and reactive load on excitation, watching frequency hold.
Surveyor follow-up: lamps bright at the close attempt — shut or wait, and what happens if you shut now?
Full theory: Diesel Generator Starting Procedure & Alternator On-Load | Marine Guide -
7 Generator getting overloaded ,what is the
Also asked: “Overloading of generator”, “Generator overloading what will happen”
Answer
Overload sheds hotel load in stages before the board dies: preferential trips first, main breaker last.
- Preference-trip relay alarms then trips staged non-essentials — galley, accommodation, deck and reefer groups in order.
- Generator near 110% starts the sequence; near 150% the main breaker guards the set itself.
- Essentials never shed: steering, navigation, alarms, emergency lighting and fire pumps ride through.
- Prove by staged-trip test with seconds logged per group — unfired preferentials fail the blackout drill.
Surveyor follow-up: blackout with preferentials unfired — relay, settings or wiring, and what proves it?
Full theory: Diesel Generator Starting Procedure & Alternator On-Load | Marine Guide -
8 Sketch and deseribe the operation of a governor suitable for diese! generator. (16
Answer
Sketch flyweights against speeder spring driving fuel through pilot valve, buffer and terminal shaft to the rack.
- Flyweights spin with the engine and fling outward with speed against the speeder spring.
- Thrust block compares actual against wanted speed with buffer springs damping the hunt.
- Pilot valve meters oil to the power piston on the terminal shaft; droop lever trims sharing with sisters.
- Draw drive gear, oil pump, compensation lands and rack linkage in operating order with droop marked.
Surveyor follow-up: hunting with the speeder set right — buffer, oil or droop, and what do you adjust?
Full theory: Governing and Speed Control — Droop, Load Sharing and the Overspeed Trip -
9 Three lamp method of synchronizinf full
Also asked: “) 3 lamp method of synchronizing”
Answer
Three lamps prove volts, frequency, phase and sequence: sequence rotation shows fast or slow, dark-bright together means ready.
- Lamps wired across phases A-to-B, B-to-C, C-to-A for the sequence method with brightness rotating with slip.
- Clockwise rotation means incoming fast, anticlockwise means slow — trim governors to slow the dance.
- All bright and dark together with correct sequence marks the closing instant mid-bright.
- Two-bright-one-dark variant cross-connects two lamps for the same answer with different wiring.
Surveyor follow-up: lamps rotate fast clockwise with volts matched — faster, slower or close now?
Full theory: Brushless Alternator Working, Paralleling & AVR Explained -
10 Generator overspeed trip
Answer
Generator overspeed trips near 10–15% above rated: no auto-reset, manual reset only after the cause dies.
- Set near 110–115% of rated with main-engine sisters capped near 110% — quote your ship’s figure, not the band.
- Prove by lowering the setpoint and driving speed up on the governor knob, or by false ramp signal on electronic governors.
- Never prove at true overspeed on load — the test proves the trip, not the engine’s courage.
- Reset by hand after investigation with fuel, load-sharing and governor proved before paralleling again.
Surveyor follow-up: trip proved by knob with the setpoint never restored — protected or unprotected on the next run?
Full theory: Governing and Speed Control — Droop, Load Sharing and the Overspeed Trip -
11 Sketch a lamp-bright configuration synchronizing lamps
Answer
Draw the bright-lamp cross-connection: lamps wired across unlike phases so full brightness marks exact synchronism.
- Cross-connect lamp terminals across the paralleling breaker so unlike phases face each other.
- At synchronism the voltage across each lamp equals system voltage — lamps burn brightest at the closing instant.
- Off-sync the lamps pulse bright and dark at slip frequency; slowing pulsation means governors nearly matched.
- Rate each lamp at full system voltage since synchronism puts full volts across every lamp together.
Surveyor follow-up: lamps brightest with the synchroscope reading 6 o’clock — close now, wait or rewire first?
Full theory: Brushless Alternator Working, Paralleling & AVR Explained -
12 Compression Pressure of Your Generator engine
Answer
Compression pressure is the cylinder’s health report: it is taken on the indicator at a shut-off load and compared with the maker’s figure.
- The indicator card gives the compression line, and its height on the shut-off card is the compression pressure.
- It is taken with the engine warm at a fixed load, because the reading moves with temperature and with the load.
- Low compression on one unit means rings, valves or a liner; low on all units means the whole engine is worn or the fuel is poor.
- Spread across the bed at steady load is the finding — a healthy set reads within a few per cent unit to unit.
Surveyor follow-up: compression down on three units with the fuel changed last week — engine wear, injectors or the fuel first?
Full theory: Marine Fuel Testing, ISO 8217 & Combustion Analysis -
13 Generator rating and voltage control
Answer
Rate the set in kVA at a power factor, and hold the voltage by trimming excitation through the AVR against the load.
- The nameplate gives kVA, voltage, frequency and power factor; kW follows as kVA multiplied by that power factor.
- A rise in load drops the terminal voltage, and the AVR increases field current to bring it back.
- The series-compounded input also raises excitation as load current rises, so voltage is held approximately constant.
- Static AVR units trim out the residual deviation from internal effects and load wander, giving the close regulation expected.
Surveyor follow-up: voltage sagging 20 V on load with the AVR proved healthy — is the excitation, the field or the load?
Full theory: The Alternator and Switchboard — AVR, Load Shedding and the Automatic Plant -
14 Synchronisation of generator Equipment used to measure ir
Answer
Synchronising needs the synchroscope, the lamp method and the ammeter: the pointer shows the result, the lamps the sequence.
- The synchroscope shows the phase difference and its direction, so 12 o’clock means synchronised and the rotation shows fast or slow.
- With the three lamp method the sequence must appear to rotate slowly clockwise, and synchronism is the top lamp dark with the two lower equally bright.
- A traditional pointer synchroscope is short-time rated, often up to 20 minutes, so switch it off after paralleling.
- A correctly synchronised incoming machine also shows almost no kick on its ammeter — the simplest confirmation there is.
Surveyor follow-up: lamps rotating anticlockwise at closing — is the incoming machine fast, slow, or out of phase?
Full theory: Brushless Alternator Working, Paralleling & AVR Explained -
15 Voltage not appearing when generator started What will u check and how will you do field flashing
Also asked: “Generator not producing voltage reasons How to do field flashing”
Answer
No voltage means no build-up: check residual magnetism first, then diodes, brushes, AVR and excitation, and flash the field if needed.
- Causes are loss of residual magnetism, failed rectifier diodes, malfunctioning slip rings or brushes, a faulty AVR, or lost excitation.
- Residual magnetism is lost through shelf time or improper operation, and without it the exciter never starts building.
- Flashing the exciter field with a 12-volt battery restores that magnetism and the voltage builds from there.
- Check the excitation supply and the AVR before flashing — flashing a set with failed diodes achieves nothing.
Surveyor follow-up: flashed the field twice with no voltage and the diodes tested good — what is left to check?
Full theory: The Alternator and Switchboard — AVR, Load Shedding and the Automatic Plant -
16 Which type of ig ? Ig generator
Answer
Name the ship’s inert gas plant and how it is used: a scrubber-type or oil-fired plant, cleaning the gas for the cargo tanks.
- A scrubber-type plant cleans the gas with seawater, a demister and a deoiling filter before it goes to the deck main.
- An oil-fired or gas-fired type incinerates the vapour and delivers it hot — effective on some types, restricted by the rules.
- The gas is delivered to the cargo tank main, kept slightly positive so air never enters the cargo.
- A tanker with no gas-fired plant must be inerted by the approved scrubber or nitrogen generator, proved before cargo is loaded.
Surveyor follow-up: tanker loading without a proved inert gas plant — can the ship complete, and on whose authority?
Full theory: Deck Foam & Inert Gas (IG) Systems on Tankers -
17 what is synchronisation? Why need to do it?
Also asked: “What is synchronizing?”
Answer
Synchronising is matching voltage, frequency, phase and sequence before closing, so the incoming set never takes a circulating current.
- The incoming generator voltage must equal the busbar voltage, and its frequency must match the busbar.
- In three phase the phase sequence must also match, and the phase itself must be at the closing instant.
- The synchroscope shows the result: 12 o’clock is perfect synchronism, 6 o’clock is out and must not be closed.
- The switch is closed just before 12 — at 11 — because slip is approaching zero and the closing time carries it to synchronism.
Surveyor follow-up: needle rotating slowly clockwise and never holding 12 o’clock — fast, slow, or out of phase?
Full theory: Brushless Alternator Working, Paralleling & AVR Explained
Source: 123 written papers and surveyor oral banks, 24,613 entries, merged into 17,210 topics. Ticks are stored on this device only.