Generator Voltage Drop

Check for the following -

1. Engine fuel pipe free from the dust, Similarly the Fuel filter free from the dust / impurities of the fuel.

2. Check the load pattern, Is some additional load is being put on the generator during this period.

3 Does this phenomon happens at early hrs of the day, when % of Humidity is high. The high humidity can affect the performance of the AVR of the alternator.

I been a cat mechnic for some forth years,it sound like the engine has a internal problem like valve steam excess wear bad injectors. also the engine needs a new set of rod and mains rolled in and turbo seals and bearings need to be replaced,if you check the spec.on engine the turbo is out of spec. also check low oil pressure shut down switch. the engine is diffently not making the required hourse power to maintain required load.

Check on the loads carried by the generator, it might be overloaded. the kind of loads also matters, starting of very large motors can also give such an impact at the start but after picking up it demands less current and hence stabilizing. this causes an increase in generator speed due to sudden reduction in load demand .pliz check on the loads fed by it

TOMNO

Generator is running 50% of the day. Mostly it starts with the lights twinkling during 30 min, than the voltage drops and also freq. this during 5 minutes. When engine picks up again it is like rpm is going far too high, high current going through the circuit and frequency going to 55-56Hz. I presume therefore one sensor makes the engine shutting down immediately.

We are changing filters weekly now, but seems that this doesn't help. Note that generator is having 9000 Hrs and producing lot of blue smoke.

Thx for your help

<...producing lot of blue smoke...>

Then it may be working harder than it can get air through it to burn the fuel. What does the original equipment manufacturer have to say on the topic?

This may indicate that the fuel-to-air ratio is incorrect, resulting in a loss of power and an inability to perform at the rated output, thereby invoking the described shutdown behaviour.

Since Hz also drop it means RPM definatly gose down as Hz are directly related to RPM and nuber of poles number of poles are fixed hence only RPM. It means th engine is unable to taqke the load which could be excessive at particular time such as starting of some load a that time look for such load. is it ocuring particular time of day? - may give a clue to some routin activity responsible fopor the load. When engine is tring to send more fuel to restor RPM it maqy give lots of black smoke but blue smoke indicates burning of oil. This lots must have been tripping it self resulting in high RPM as immediate response

I was not clear if the engine RPM drops before the voltage problem, if so there is a fuel actuator / governor on the left side of the engine (if you are at the front facing the engine). also check the linkage to this actuator, I have seen the linkage worn bad enough to affect the operation of a engine. To replace the actuator unit as a whole. I don't know what year or ser # your unit is ( for S/N 9NR1 - up part # 7E-0598 24volt or 111-4421) also check for air leaks in your fuel system, air filter and fuel pressure. If the engine RPM is not dropping off before the voltage drops it sounds like it is your voltage regulator they can act up for an extended amount of time and then one day it may drop voltage completely. I don't remember the part #s for a voltage regualor.

I hope this helps.

If you are seeing lots of blue smoke as the engine warms up this is a good indication that crankcase oil is now becoming unmetered fuel. yes tired diesel engines will run on there own crankcase oil and throttle and gov. inputs can no longer provide stable rpm control. check with your cat dealer but this engine has passed some maintance milestones along time ago ie. valve adjustment, overhead adjustment ,bearing replacement,ect....you may also be introducing oil into the fuel supply from injector orings

Is the engine governor mechanical or electronic, check for wear on gov linkages and the governor itself. Check pump timing and gears for wear and play.

Is the fuel shutoff solenoid operating fully and releasing fully.

If electronic governor, then check electonics for a loose wires making intermitent connection. also wiring of AVR if fitted

How does a compression test look? is excess oil coming up past worn rings or down past worn valve stem seals. Is the engine smoking? what color?

Is the air filter a paper cartridge or oil bath type, overfilled or clogged.

Get an engine repair manual and follow troubleshooting section.

Have ur complete actuator system and the speed tranducer checked.

Dickson

The Caterpillar 3306 model engines are presently starting with 200 kva ratings. 180 KVA 3306 engines means very old. The RPM hunting problem is in two fold. One is due to governor sluggishness due to load hunting in nature and other is due to fuel system defect. i.e.due to chocking of fuel filters or due to restriction in the fuel lines and the water contamination. Both the governor problem and fuel problems to be identified and addressed properly.Once the load is thrown off, or the movementary fuel restriction is clear or the governor gets back to the normal situation, the speed of the engine will pick up and before it gets back to the set value, the engine touches the overspeed trip point and engine trips off.Pl. note once the engine speed drops the voltage also proportionately drops.

Regrds,

CVS Murthy

09866550981

Thanks to all for your tremendous guidelines, it appears that the governor,fuelpump and injectors need overhauling, but at 9100 hrs running in Africa with not always clean FO , time to open up I guess.

Now new installed Gen is running (250 kVA) all appartments are lightening very bright , never been like this since I am here.

Fuel purifier and waterseparator (Racor) will be installed to assure clean FO supply to the gen.

Thx again !

You might consider to check your speed regulation system, i.e. governor, check also fuel line system as this may caused by filter or line blocked.

what type of avr you have?