Diesel generator low voltage output

[vas]

ah, sorry, yes stuck in my mind that it is working, forgot the 170V...

 

[Beneteau381]

Thought it was yet another urban myth. If it's a single exciter circuit (no matter how it's implemented) having already 230V as is, means it's somehow done it's job, no?

Urban myth its not, Saudi Arabia camp in the desert genny, got that going by flashing it. Angola, CAT 3306, similar.

 

[QBhoy]

No AVR. Super simple control system. Engine is running at 3060rpm. Checked on laser rpm device I carry. Voltage is trimmed with capacitor. It has the correct one fitted and I have swapped it out for spare new one with no change. The workshop manual says possible causes are diodes or windings. At 27 years old I suspect windings. Also realised the engine has been running hot as the fresh water pump is leaking so the hot engine block may have pushed the winding temperature up just enough to over heat them. We are in the Caribbean with high ambient so everything is super hot

That makes sense to be fair. Good chance the windings have gone, knowing this info above. Hopefully you could possibly get a decent motor or alternator refurb place to sort you out.

 

[Zing]

Our 5Kva diesel generator is playing up. At no load it's producing 170v. It's capacitor controlled so I swapped the capacitor and it's just the same. If I run the water maker, 1.5kw motor, the volts drop so low it stalls the motor. We can run the battery charger or immersion heater all be it at 170v.
I am guessing winding fault? The alternator is about 27 years old. I replaced the diesel engine about five years ago but kept the alternator.
Any experts out there? I am thinking of taking the alternator off and getting it to a rewind shop here in Antigua. Any thought welcome

Fitzroy’s in St Johns. Best shop on-island for this sort of thing, electrical. Rough and ready, be warned

 

[geem]

Fitzroy’s in St Johns. Best shop on-island for this sort of thing, electrical. Rough and ready, be warned

Yep, that's my option. Had them recommended.
Thanks

 

[ARE]

depending on brand, @ARE is working for ONAN (IIRC) maybe worth asking.
If it's not got any fancy AVR I'd guess a loose cable sort of making contact but not able to get the power through?
Got an inverter to soft start the watermaker motor? if so maybe an issue there?

Normally speaking a winding failure would give you no voltage or very low voltage, 170V is neither. What size capacitor is fitted? Have you tried the next size up? Sometimes the tolerance is not very good and the next size up fix’s the problem. The engine speed should be 3200rpm with no load.

Have you measured the winding resistances, are they within spec? You don’t need a Wheatstone bridge.

 

[geem]

Normally speaking a winding failure would give you no voltage or very low voltage, 170V is neither. What size capacitor is fitted? Have you tried the next size up? Sometimes the tolerance is not very good and the next size up fix’s the problem. The engine speed should be 3200rpm with no load.

Have you measured the winding resistances, are they within spec? You don’t need a Wheatstone bridge.

The generator has been running perfectly for several years with the current capacitor. No load voltage is 240v. With a large inductive load the voltage gets down to about 210v. I did increase the size of the capacitor several years ago but you can only trim the voltage by 10% with a capacitor.
Something has clearly failed since no load voltage is now 60v lower than previous. The manual says engine rpm should be 3000rpm. It's actually 3060rpm.