Replacement VR3 Regulator With VR6

It's important that you verify that all CT and PT polarities are correct from ech device back to the regulator. Did you swap the leads on the droop transformer? That's usually where the problem is when everything works fine individually but not in parallel.

From your http://cr4.globalspec.com/thread/59780/Replace-CAT-VR3-Regulator-with-VR6 you were going with a CDVR, did you do that before going back to the VR6? Though in my experience it's not much better than the VR6 and just a coppy of the Basler that takes Cat software to program unless you install the CDVR in the Cat then you can use CAT-ET to program the CDVR, was just out on a job doing that on an AC Rig here, a PIA IMHO.

But back to your problem: what kind of SCR's and are you still getting the spiking, is your Gai Tronics all buzzed out when you go up with an empty hook? That's usually caused by grounds in the 480 MCC and can cause VR's to go nuts. Put your ScopeMeter on the 120 and look for overshooting after the notch from the SCR's firing, steady losd of a MP is the best to look at but up the empty hook puts the most load for the first 2-3 seconds.

Do the checks above [CT on the right phase to the PT's] and make sure the VR6 is set for the right CT ratio. You know that's the single CT usually in the Gen Pot Head.

PS, this isn't one of the rigs WD at S&S bult for the Croatians?

Thanks for your response

SCRs are GE Power drill 2000 made ​​in S & S. We did not install CDVR regulators. We installed the VR6 and they are connected as per sketch and tested over the brine tank .Everything was OK.

During the DC motor ( Drawork ) running, overvoltage was occurred (670V), but all the time during the DC motor running, voltage was increased. We have swapped the leads on the CT but no change, still high voltage.CT is in phase B. Sensing voltage is connected as per drawing. We do not useVar/ PF conntrol. What is your opinion, is this drawing fine.

So it is one that S&S built with the DC2000's, i was out on one off ENG W Africa a few years ago. Where are you drilling now?

I'm GE-Charlie but not with S&S anymore but Brian is still there. I'm going to get with him tomorrow about this, he's a better gen man than me.

Let me go over my VR6 books and I'll get back with you here.

How did the adjustments go on stability?

Going over the drawing, I'm thinking that the PT you show [on A-C closest to the generator] should be a CT or am i missing something. Do you have a single phase PT in this with the 3 phase PT?

never mind, NOW I see that's the power for the VR since it's not a PMG setup, me bad.

From what i can see of the drawing it looks right, but the VR should be tuned for the DC2000 SCR load, it's a lot diferent than the resistive salt bath load. Have you tried retuning it under the drilling load?

Charlie I'm glad to have met you through the forums. Brian has installed SCRs on OFSHORE unit semi sub Zagreb1 together with Ralf. My name is Zeljko and I am working in CROSCO (Drilling Company). Rig is in overhaul at the shipyard and we are trying to adjust VR6 regulators running mud pumps and drawork. Stability pot is at 50%, droop is same. As per drawing we have installed 2 single phase PTs for 3 phase sensing.

Thank you very much , Regards to You and Brian.

Keep us posted on how the tuning is going with the MP's Zeljko, work on the set point for voltage under the MP's and see if it holds with hotel load. Just the load going up through the Choke Manifold, all you can do at the shipyard.

If things don't start looking better tuning with the SCR load there must be something else wrong, most likely with the wiring, and it's with all the units from what you have said.

It worked with the VR3's, should work with the VR6.

I'm the GE man [need advice with Toolbox? I bet I still have your drive files], Brian is a better VR man, we'll see what he has to say after he sees this.

For sure these Cat VR's don't tune well on a resistive load, same with the Woodward EGCP-1's, that's what I was just dealing with in NM last week. The salt tank is good for KW load testing/sharing, not so much for the KVAR's that the VR takes care of.

What are your you using for a speed regulator, a Woodward EGCP-1 too?

Good luck, hope you have more shipyard time to work on this.

speed regulator is 2301A - analog.

OK Charlie , thanks

PS. Charlie if you or Brian have the exact wiring diagram for VR6 connection please send me.

Here's the VR6 manual from CAT http://www.scribd.com/doc/31979850/Caterpiller-AVR-VR6-User-s-Manual , I'm looking for the Basler equivalent; their manuals are MUCH better and more accessible that CAT which is why we seldom work on the Cat VR's. But from what I can see its wiring is the same as the VR3. The CAT people are such PIA's getting help from with out bringing out a Field Engineer with CAT-ET then he'll be calling in, but you may need to for this, GE and/or S&S Engineers aren't going to be able to give you "exact wiring" for your application, wherever you are there should a CAT shop, just like S&S.

The big test will be tuning the VR6 on the SCR load, does it start getting better? If you can't tweek any improvement with VLT-ADJ, STB, UF, or DRP you have a wiring/PT/CT problem. Maybe you do need the CDVR that can be set for more modes of operation, remember those SCR's have terrible PF and the KVAR's will almost equal the KW's, AVR's hate that.

Thanks for your concern about our problem.
We shall check wiring of CT and PT again and try to adjust the regulator at load on SCR
I will inform you about results.
Regards

Brian thought you might check that the voltage output matches the ohms of the field.

like

63 volt model = 5.3 ohms

125 volt model = 12.5 ohms

but still boils down to needing a CAT Engineer to check your application if you don't get any joy from tuning or find a wiring mistake. Good Luck

PS from the http://cr4.globalspec.com/thread/59780/Replace-CAT-VR3-Regulator-with-VR6 post it looks like you have been working on this for over a year Ziljko, think it's time to get a Cat Engineer to the rig, everything is Cat but the 2301

Thanks for Brian advice.

Excitation coils were connected in parallel on old VR3 regulator ( aprox. 3 ohm ) After mounting VR6 regulator windings F1-F2 and F3-F4 are connected in series ( aprox. 12 ohm ). I found this notice in the manual ( Minimum resistance forVR6 regulator is 6 ohm )
P/N for VR6 regulators which are installed:CAT 309-1019 VR6
Output: 65V - 12ADC Power input: 180-280V 1 or 3 phase Sensing voltage: 180-280V 1 or 3 phase CT 1-5A

How many amps are you drawing?

If it's over 8 or 9 sometimes I would try to get a series/parallel wiring of the coils to get closer to the 6 ohms to match what your 65V flavor VR is looking to work best at. That said I don't see that being "the" cause of the overvoltage at the high KVAR's your driving with the SCR load. Check the amps.

We did not check amps on exiter

We have only two choices. Connect in parallel (3.5 ohm) or serial (13 ohm). Each coil is 6 ohm.

Tomorrow, we will measure the amps

Regards

Just thinking about your generator controls, not related to the VR problems but your analog 2301's. IF your 3500 Cats have electronic fuel injectors you should think about an upgrade to 2301D's; trust me. I've done a few GE retro fits to the digital EGR in place of the old analog GEM generator controllers and after the change them the rig could drill over a 1000 feet farther before they had to put another Cat on line. The digital speed controller, combined with the quick reaction of the Cat Electronic rack, allows for more precise KW sharing that it looks like the KW load goes down: just something to think about while you're fighting all this.

Going digital doesn't help the VR with AMP/KVAR sharing from what I've seen. I think it has to do with the cubic response of flux field to the excitation power, too slow. Want to talk about the Flux Capacitor? That can't be improved with hardware like going to electronic rack control instead of the old mechanical actuator on the fuel injectors.

Too much time on my hands right now, sorry Ziljko . You got any bathtubs you need broken? We'll get some real work when you load them down and see how tweaking the pots work, I'd look carefully at what happens when you play with droop.

I wish a CAT Service Engineer would jump in here and give you some specific information on the wiring differences between the VR3 and VR6. Especially the Droop and Cross Current. With the voltage going up I'm thinking there are wiring problems there. I gave RAMConsult a GA for bringing it up in the first post before I hijacked this thread.

Really appreciate your concern about solving our problems. If we know the difference in connection VR3 and VR6 regulator we could solve our problem. I came to the rig and tomorrow I'll check the wiring and try to adjust droop and stability.

Regards