×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Cat 3306 - VR3 Troubleshooting

Cat 3306 - VR3 Troubleshooting

Cat 3306 - VR3 Troubleshooting

(OP)
I have a new problem with my power plant on the boat. Had some maintenance done, including insulation tests. Went to put a generator on the bus and it wasn't producing voltage. Suspected fuses on the VR3, and sure enough they were blown. Put new ones in, switched it into auto mode and saw it start to ramp up voltage on the voltmeter and then dropped down to 0 again, fuses blown again. Figured the AVR is dead, wrangled up some "new" VR3's and have tried two different ones, not blowing fuses now, but not producing voltage either. Tried setting it over to manual (it's a 7C2700 controller on my swbd), still no voltage. Took some readings off the F1 & F2 and getting essentially 0 coming out (like 230millivolts). The L1 exciter stator is reading 4.2ohms so that appears to be good and resistance to ground on it shows OL so that's good too.

I've got a sneaking suspicion i've got a bad diode on the RFA but just want to exhaust all my options before I have to pull a bunch of stuff apart to get access to them.

And yes, I know the VR3's are obsolete, but it's what i've got and upgrading to VR6's at this time is last resort since it would be like a 150+ man hour job with the necessary cable runs and interferences. It's going to happen, just...not now.

Any other tests to do to nail this down further, or time to bite the bullet and get into the RFA and start testing diodes?

RE: Cat 3306 - VR3 Troubleshooting

Quote:

And yes, I know the VR3's are obsolete, but it's what i've got and upgrading to VR6's at this time is last resort since it would be like a 150+ man hour job with the necessary cable runs and interferences. It's going to happen, just...not now.
And upgrading to a VR6 still won't cure bad diodes.
Did someone megger the field without disconnecting or shorting the rotating diodes?
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

RE: Cat 3306 - VR3 Troubleshooting

(OP)

Quote:

Did someone megger the field without disconnecting or shorting the rotating diodes?

My question as well. No way to ever know for sure since I wasn't standing there when it was done. They did meg the field (F1 & F2) to ground, and the instructions include making sure those connections are lifted from the AVR prior to doing so. And these are guys I trust and they do it for multiple other boats with the same set up (except they have the VR6 upgrade done), so it's not like they're running around blowing up AVR's left and right. Accidents happen and i'm not mad, just trying to get this gen up and going again so we can get underway and work these buoys on the lakes.

RE: Cat 3306 - VR3 Troubleshooting

Found AVR's are usually dead AVR's. They don't get removed from service in working condition.

Diode Failure Scenarios Modes of Failure, Causes and Effects - MER Equipment https://merequipment.com/wp-content/uploads/Diode-...

If you expect diode failure, inspect them before running the unit again as diode failure can cascade into exciter and rotor failure.

Are you getting a partial voltage form generator when it is completely unloaded? Residual magnetism should produce some voltage. If you are seeing none then the stator is shorter.

RE: Cat 3306 - VR3 Troubleshooting

(OP)
In general I agree, with found parts generally being unreliable. In this case, I know some of the ones I received were uninstalled to do a conversion to new digital voltage regulators.

Got into the gen today, pulled all the diodes, tested them, all were good. Since I had the end bell off, went ahead and gave the exciter stator windings a gentle wipe down. Tried flashing the field as per the manual with a 6 volt lantern battery. Moved on to next step as per the manual which was to hook up a big 12v battery to the F1 & F2 connections for the field winding and then ran the gen at half rated speed (900rpm), which it did start putting out voltage on the sensing lines, saw 139vac across 20 to 22, for reference my working gen reads 240vac across 20-22 and about 120ish on each individual sensing line. when it's at rated and in auto voltage mode. Moved on to next step, took the voltage droop rehostat out of the loop, remote voltage adjust knob out, put the jumper in from 4 to 7, took the voltage controller at the swbd out of the loop so the only thing hooked up to the avr was the voltage sensing lines and the exciter. And nothing. I'll see like 8 or 9 volts on the sensing lines and like millivolts dc on the F1 & F2 when running at rated speed (1800rpm). So i'm at the point where it says to fabricate a tester for the AVR using a 240vac source, a 100w bulb and a switch. Probably going to have a tougher time finding a 100w incandescent than getting those AVR's since everything is LED nowadays.

When you say partial voltage from the generator unloaded, do you mean partial voltage on the sensing lines with the engine stopped, or engine running? Or do you mean partial voltage on the exciter stator winding?

RE: Cat 3306 - VR3 Troubleshooting

Quote:

I'll see like 8 or 9 volts on the sensing lines and like millivolts dc on the F1 & F2 when running at rated speed

Quote:

Found AVR's are usually dead AVR's. They don't get removed from service in working condition.
There may be a connection here.

Quote:

When you say partial voltage from the generator unloaded, do you mean partial voltage on the sensing lines with the engine stopped, or engine running?
Engine running at rated speed.
This is based on the assumption that the sensing lines are still properly connected to the generator windings.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login



News


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close