PANCAKE GENERATOR - Marathon Electric

i. Check generator frequency (speed) under load.Adjust as necessary. (Refer to prime mover/governormanuals)Shut down procedures.There are no specific instructions for shut down of thegenerator; however, several good engineering practicesshould be observed to prolong equipment life.a. It is advisable to disconnect all loads (open maincircuit breaker or disconnect) prior to shut down.This is especially important if loads can be damagedby low voltage and/or frequency conditions duringgenerator “coast down”.b. Isolate any condition that could allow the generatorto see a voltage at its terminals while at rest.Failure to do this could result in personnel injury orequipment damage.MAINTENANCERoutine MaintenanceYour Marathon Pancake generator has been designed tobe as reliable and trouble free as is possible. However,costly repairs and down time can be minimized byoperating the unit under conditions that are compatiblewith those at which the equipment was designed tooperate (See OPERATION section). The followingmaintenance procedures should be followed to insurelong equipment life and satisfactory performance.a. Routinely check intake and exhaust air screensto insure that they are clean and free of debris.Clogged intake air screens will reduce coolingairflow and may result in the unit operating atdangerously high temperatures which reduce thegenerator’s life. This inspection and cleaning shouldbe done in conjunction with prime mover air filtercleaning and/or change‐out.b. Periodically (approximately every one thousand[1000] operating hours) check the bearing(s).Pancake generators are equipped withprelubricated‐for‐life bearings which do not requireroutine lubrication.c. Periodically inspect the unit for buildup ofcontamination (dirt, oil, etc.) on the windings. Ifthe wound components have become coated withheavy concentrations of oil and grime, the unitshould be disassembled and thoroughly cleaned.This operation is not one that can be accomplishedeffectively on site, but rather one that should beconducted by an authorized service center equippedwith the appropriate apparatus and solventsnecessary to properly clean and dry the generator.d. Periodically, about once every 2000 operatinghours, or in conjunction with scheduled enginemaintenance, check the DC no load excitationvoltage. Compare this voltage with the valuerecorded during initial startup. If this value of noload excitation voltage is markedly higher than thebenchmark reading, it is an indication of problemsin either the exciter field, main field, or possibly therotating rectifier assembly. Insure that voltage andrpm is the same as initial test conditionDrying Generator WindingsGenerators in service may inadvertently have theirwindings exposed to splashing or sprayed water. Unitsthat have been in transit or storage for long periods oftime may be subjected to extreme temperature andmoisture changes causing excessive condensation.Regardless of the source of moisture, wet windingsshould be thoroughly dried out before operating the unit.If this precaution is not taken, serious damage to thegenerator can result. The following procedures may beused to effectively dry the unit’s windings:a. Electric space heaters can be installed inside thegenerator frame. When energized from a powersource other than the generator itself, they will heatand dry the inside of the generator. If an alternatesource of electricity is not available, enclose the unitwith a covering, and insert heating units to raisethe machine’s temperature 15°F to 18°F (8°C to10°C) above the outside temperature. Leave a holeat the top of the enclosure to permit the escape ofmoisture.b. If the windings are damp, but not saturated, run theset for approximately 1 to 2 hours with excitationoff (AVR power supply open). If the windings havebeen saturated, a portable air heater can be usedby directing heat into the air intake openings, andrunning the set with no load and the excitation offfor several hours. Heat at point of entry should notexceed 150°F (66°C).SERVICEGeneralThe service procedures given in this section arethose which can reasonably be conducted on-sitewith a minimum of special tools and equipment. Allservice procedures should be conducted by qualifiedmaintenance personnel.8