Help with Leroy Somer alternator
Help with Leroy Somer alternator
(OP)
We are in the process of trying to recommission our diesel generator after undergoing mechanical repairs. The recommissioning process requires that we run the generator at sliw speeds for short periods of time off load. Gradually increasing the speed untill we reach full speed 1500 RPM, then gradually apply load.
The alternator connected to the engine is a Leroy Somer TYPE LSA54-XL95-4P and generates at 11000 Volts.
Now we ere running the engine and alternator at low speed, with the alternator diconnected from busbars/load. I noticed that the alternator ammeter is trying to drive downscale below the zero. I also noticed that the alternator housing us getting a bit warm (62 deg C), so I have shut downn the engine.
Can anyone advise on why the alternator is getting warm? I have a feeling that I may need to dicconnect the excitation. If this is correct, can anyone advise how/where is best place to disconnect the excitation. Also, is there anything else I need to be aware of?
The alternator connected to the engine is a Leroy Somer TYPE LSA54-XL95-4P and generates at 11000 Volts.
Now we ere running the engine and alternator at low speed, with the alternator diconnected from busbars/load. I noticed that the alternator ammeter is trying to drive downscale below the zero. I also noticed that the alternator housing us getting a bit warm (62 deg C), so I have shut downn the engine.
Can anyone advise on why the alternator is getting warm? I have a feeling that I may need to dicconnect the excitation. If this is correct, can anyone advise how/where is best place to disconnect the excitation. Also, is there anything else I need to be aware of?





RE: Help with Leroy Somer alternator
For low speed tests, add external cooling devices.
RE: Help with Leroy Somer alternator
I hope that your AVR has Under Frequency Roll Off. UFRO has been standard for many years now, but there are still a few AVRs in service without UFRO.
The old AVRs would generally fail in less than a minute if the set was operated at slow speed. Failure may result in the maximum current being applied to the field.
Even with UFRO, the AVR will be driving the field.
I would disconnect the power in to the AVR rather than the output to the field.
Bill
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"Why not the best?"
Jimmy Carter
RE: Help with Leroy Somer alternator
Do you have the manual for this generator? Here is the general manual for this range, http://www.leroy-somer.com/documentation_pdf/2327_...
Where is the reading of 62C coming from? is that the surface temperature of the housing or a reading of a stator temp?
What voltage regulator is installed, normally these units shipped with the AVR449, but depending on its age it may also have a digital regulator, either should have the UFRO feature Bill described, but it may not be properly adjusted.
How long was the unit down and in what environment? It happens occasionally where a unit this size has been shut down for service with the generator space heaters not working and when restarted a failure occurs. Older units or units in coastal areas or in marine applications as those most affected.
Have done any electrical testing on the generator? I think some basic checks as described in the manual may be in order before you try to proceed further.
Hope that helps, MikeL.
RE: Help with Leroy Somer alternator
Back to the set at hand. Due to core damage, neither set ever ran again.
Further to Mikes comments, The set may have developed turn to turn shorts. What may fail explosively at rated speed, may develop heat at slow speed.
The good news is if you do have failing or failed windings, the unit may not have yet suffered core damage and so be rewindable.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Help with Leroy Somer alternator
RE: Help with Leroy Somer alternator
Good luck,
MikeL
RE: Help with Leroy Somer alternator
RE: Help with Leroy Somer alternator