Arcing on gen engine block fault
Arcing on gen engine block fault
(OP)
Got a pretty decent fault today. Thought ild share.
Background and fault:
Conducting a inspection of a 175kVA gen set. Gen is reasonably old. It has come back from a site where is was run underloaded and not serviced regularly. Has a number of oil leaks and we are considering writing it off. Once we fixed a start fault we heard some ticking. We localised it down to a small arc from the base of the crankshaft pully to the engine block. Arc happens at 2 to 4 second intervals. Quite a strong arc since we could see it clearly even with sunlight. We noticed our RCD had a fluctuating display of .5mA to 1.2mA.
Initial fault finding.
Initially thought that the battery alternator may be screwed so we disconnected it and ran gen off the battery. No change
Thought than maybe the gen alternator may have a fault so tested winding continuity, insulation resistance and earth continuity. No change.
Thought than since the gen is filthy, that the belts may be somehow causing a static charge to develop. Cleaned the gen and arcing disappeared however RCD still indicates a fluctuating earth current.
Still not convinced we had actually fixed the fault, we tested the RCD current transformer. Continuity checked out. Point to note the arrow on the tranny pointed away from the star point on the gen. Turned it around yet no change.
Considered testing the RCD however didnt have any spares and it passed a the RCD test.
Background and fault:
Conducting a inspection of a 175kVA gen set. Gen is reasonably old. It has come back from a site where is was run underloaded and not serviced regularly. Has a number of oil leaks and we are considering writing it off. Once we fixed a start fault we heard some ticking. We localised it down to a small arc from the base of the crankshaft pully to the engine block. Arc happens at 2 to 4 second intervals. Quite a strong arc since we could see it clearly even with sunlight. We noticed our RCD had a fluctuating display of .5mA to 1.2mA.
Initial fault finding.
Initially thought that the battery alternator may be screwed so we disconnected it and ran gen off the battery. No change
Thought than maybe the gen alternator may have a fault so tested winding continuity, insulation resistance and earth continuity. No change.
Thought than since the gen is filthy, that the belts may be somehow causing a static charge to develop. Cleaned the gen and arcing disappeared however RCD still indicates a fluctuating earth current.
Still not convinced we had actually fixed the fault, we tested the RCD current transformer. Continuity checked out. Point to note the arrow on the tranny pointed away from the star point on the gen. Turned it around yet no change.
Considered testing the RCD however didnt have any spares and it passed a the RCD test.





RE: Arcing on gen engine block fault
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Arcing on gen engine block fault
Getting to the diode pack on the rotor isnt a easy task and im unsure what output or result ild get.
Point to note, I loaded the gen today and once it got past 180A/phase (Full load is around 240A) the RCD current increased steadly over a few minutes from 10mA to 25mA which tripped the RCD.
RE: Arcing on gen engine block fault
Alternately, check for voltage on the non-drive end of the alternator shaft. You may also ground the non-drive end and measure the current. If this is a static issue a grounding device on the non-drive end may solve the problem.
If the engine bearings are badly worn you may have an air gap issue on the drive end of the rotor.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Arcing on gen engine block fault
RE: Arcing on gen engine block fault
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Arcing on gen engine block fault
RE: Arcing on gen engine block fault
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.