Main Generator Maintenance

7/31/2019 Main Generator Maintenance

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Daniel Robson T/V KINGS POINTER Revised: 6/20/01Chief Engineer Generator Maintenance Page: 1

MAIN GENERATOR MAINTENANCE

CLEANING, INSPECTION AND LUBRICATION OF AC GENERATORS

GENERAL INFORMATION AND INSTRUCTIONS:

A plaque card on the generator gives the grease replenishment amount and intervalsin both running time in hours and months, whichever is first.

READ THIS BEFORE PROCEEDING

PRECAUTIONS:

Observe all standard safety precautions associated with electrical and mechanicalequipment. .

WARNING

Verify diesel engine for generator to be cleaned and tagged out ofservice. Secure power to the generator space heaters before removing covers.

OPERATION STEPS KEY POINTS1. Remove exciter end bell Exposes exciter and

cover upper half. generator bearing.

2. Clean the inside of the generator with a Avoid blowing dirt andvacuum cleaner or use dry filtered compressed dust forward into the

air at a pressure of from 25 to 40 psi. generator when usingcompressed air.

3. Clean all ventilating ports at both ends of thegenerator with a vacuum or dry filteredcompressed air.

4. Lubricate the exciter end bearing with 1.6 ounces Lubrication is requiredof NGL 1, grade 2 electric motor bearing grease at 8400 hours or 24.through the zerk fitting on the stator frame. Months.Note: Some ships have sealed generator carriage

bearings which do not require lubrication.

5. Wipe excess grease from the grease relief valveand from around the shaft at the seal.

6. Inspect generator stator and exciter rotor and statorwindings for signs of deterioration caused by heat


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or foreign object damage.

7. Inspect tightness of mounting hardware on exciterstationary and rotating components.

8. After completion of inspection, cleaning and lubrication,replace covers returning generator to usable condition.


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MAIN GENERATOR INSULATION RESISTANCE MEASUREMENT

GENERAL INFORMATION AND INSTRUCTIONS:

Duration of application of an insulation resistance test potential should be one minutewith readings taken at the end of the one-minute test. A correction factor must beused to bring readings to a 40C value (see last page). Insulation resistance readingsshould be permanently recorded for future trend analysis.

READ THIS BEFORE PROCEEDING

PRECAUTIONS:

Observe all normal safety precautions associated with electrical andmechanical equipment.

WARNING

Disconnect load l ines and all controls from generator stator leads beforetesting generator windings.

WARNING

Disconnect all power from the 600 volt switchboard to ensure safety ofpersonnel performing this operation.

Power Sources to 600 volt switchboard

No. 1, 2, . 3, and 4, Generators - secured (Engine Room).

3 ea. 600/450 volt transformer primary breakers - open (600 VAC SWBD).

3 ea. 600/450 volt transformer secondary breakers - open (450 VAC SWBD).

4 ea. diesel generator cold start breakers - open emergency 24V SWBD(Emergency SWBD).

2 ea. diesel generator space heater breakers - open L128-4M (1 & 3),L-128-4N (2 & 4) (Main Deck Passage Way outside Officer Mess)

600 volt switchboard Lights breaker-open EL110-5G (Main Deck Passage[1-9-0] Fr. 26).

D.C. propulsion motor space heater breaker- open P412-5 (Motor Roomupper level Aft).


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M.C.S.C. Normal Power SP-107-5 (Motor Room upper level Fwd (Stbd)).

M.C.S.C. Emergency Power EP-110-10 (Emergency SWBD 120V Section)

450V. Fuse(s) FUT for bus tie interlock to 600V BT BKR.

OPERATION STEPS KEY POINTS

1. Verify 600-volt switchboard is de-energized Ensures safety of personneland will remain de-energized during this performing this operation.operation.

2. At the 600 volt switchboard, remove fuses Disconnects all controlFUAC for the generator to be tested. devices from the

Located in the generator control module. generator stator windings.

3. At the generator to be tested, remove fuses Disconnects the A.C. filterfrom the A.C. filter module. module from the generator

stator winding.

4. At the back of the 600 volt switchboard Ensures no electricalgenerator breaker compartment, verify zero shock hazard exists.volts on the breaker line bus bars.

5. Connect megger leads to test generator stator

windings to hull ground at 500 volts.

6. Record readings after one minute of megger Megger readings willpotential application, usually start low and then

increase during the oneminute period.

7. Record generator winding temperature at the This information is used intime the insulation resistance test is performed. converting the megger

readings to 40C.

CAUTIONWhen testing generator field excitation windings at terminal board CTB,terminals 12 and 13, a voltage may be present on terminals 10, 11, 14

and 15 for the generator heater. The generator heater should be securedat Panel L-128-4on themain deck.

8. At the generator control module, remove Disconnects all controlleads at CTB terminals 12 and 13, devices from the field generator


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cable marked FLD. excitation windings.

9. Connect megger leads to test the generator fieldexcitation windings to hull ground at 500 volts.

10. Record readings after one minute of Megger readings willmegger potential application. usually start low and then

increase during the oneminute period.

11. Record generator winding temperature This information is usedat the time the insulation resistance in converting the meggertest is performed. readings to 40C.

12. Utilizing megger readings and

temperatures originally obtained and the40C insulation resistance correctionfactor chart, calculate and record readingsfor future trend analysis (see last page).

13. Replace fuses for A.C. filter module andFUAC in the generator control module.

14. Reconnect FLD leads on CTB terminals Ensure leads are connected12 and 13. to the same terminals they

were removed from.


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TESTING GENERATOR POWER RECTIFIER DIODES

1. To prevent misleading test results, the diode under test should be completelydisconnected.

2. Determine if the diode under test is a "standard" or "reverse" diode by looking atthe symbol printed on the diode.

a. "Standard" diode - the threaded part is the CATHODE and the lead is theANODE.

b. "Reverse" diode - the threaded part is the ANODE and the lead is theCATHODE.

3. Connect the positive (+) lead of an ohmmeter to the ANODE of the diode.

4. Connect the negative (-) lead of an ohmmeter on the CATHODE of the diode.

The ohmmeter should indicate a LOW resistance (forward biased). Typical is about10 ohms (good).

5. Reverse the ohmmeter lead on the diode.

The ohmmeter should indicate a HIGH resistance (reverse biased). Typical is about30,000 to 300,000 ohms (good).

An ohmmeter indication of "infinity" in both directions indicates an OPEN (bad).

An ohmmeter indication of "zero" in both directions indicates an ANODE toCATHODE short (bad).


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Main Generator Maintenance