CAT SR4

[fitzoc]

HELP! Anyone know about Cat SR4 generator? I have 8 guys on an island in the Bahamas with this as only source of power; it ran for about a week and has been down for a week. We just replaced the diodes/resistor; exciter; voltage regulator -- still not working. I'm not at the site; getting info via crackly cell phone. Really need help -- none of the Cat techs seem to know what the cause of the problem is - the jumper wires are shorting out on the VR6 (brand new). Any assistance is appreciated!

 

[alehman]

What do you mean by 'the jumper wires are shorting out'? A problem with the VR6 (voltage regulator) could explain the lack of power.

 

[waross]

Start by exciting with a car batteries. First with 12 volts and if the output is less than 50% of rated output go 24 volts. Report back the output voltage and we can go from there.
Disconnect the voltage regulator completely for this test.
This will seperate voltage regulator problems from generator/exciter problems.
respectfully

 

[rbulsara]

Find CAT delaers in your area (Milton-CAT in and H.O. Penn are in the Northeast; Yancey Power in Georgia)or any neigbouring state by googling the internet and send emails to them stating what you are postin here. Give them the cell phone number and You will have much better luck and proper help.

I am sure someone from them will help you out. They are great people.

Milton-CAT in and H.O. Penn are in the Northeast.
Yancey Power in Georgia.

 

[fitzoc]

Thanks for the tips; I have little communication due to the weather. Not sure what he means about jumper wires; last time they found the jumper wires to F1 and F2 were "fried". Replaced exciter and voltage regulator; same thing again.

 

[waross]

By jumpers do they mean the connection leads?
By exciter do they mean the Permanent Magnet Generator?
If the F1 and F2 leads are heat damaged there may be serious and obvious damage to the stationary field of the exciter.
The Automatic Voltage Regulator usually self limits it's output before damage is done to the leads. It could have been a case of a faulty AVR damaging the exciter field and then the damaged field destroying subsequent AVRs.
respectfully

 

[waross]

I realize that it is probably too late in the week to contact a Cat dealer but rbulsara's suggestion has merit.
A suggestion, Cat protocol may require a US dealer to refer you to a local dealer in the Bahamas. I have had problems getting information from Cat experts in the third world and contacted Cat in the US only to be referred back to the local dealer who didn't know.
If you can contact a Cat dealer near you (Maybe the one who sold the set originally?) you may be able to chat someone up and get a tech to accept a call from the boys in the Bahamas.
I will be surprised if you can get much via e-mail, too much protocol.
respectfully

 

[alehman]

A few phone #'s...

MACHINERY & ENERGY LIMITED
COLLEGE AVE, OAKS FIELD
NASSAU,NEW PROVIDENCE I. DISTRICT
Bahamas
242 323-5701

LOGWOOD RD & PEACHTREE ST
FREEPORT,GRAND BAHAMA I. DISTRICT
Bahamas
242 352-5981 GENERAL INFO
242 352-5987 GENERAL INFO 2
242 352-5998 GENERAL INFO (Fax)


RING POWER CORPORATION
9901 RINGHAVER DR
ORLANDO, FLORIDA 32824-7040
United States
407 855-6195 GENERAL INFO
407 857-1592 GENERAL INFO (Fax)
407 438-0922 SERVICE (Fax)

PANTROPIC POWER PRODUCTS INC.
5460 OKEECHOBEE BLVD
WEST PALM BEACH,FLORIDA 33417-4542
United States
561 640-0818 GENERAL INFO
561 640-7894 GENERAL INFO (Fax)

 

[fitzoc]

Thanks Alehman; we've actually had the Nassau folks out. Tested and said it was exciter. Getting them back out will be another week. Unfortunately the US people aren't able to help (must be a Cat regional license issue). Though I've talked to a few. Haven't given up!

 

[waross]

I had two crews going in to do weekend work during an outage. Both crews needed temporary power. On weekends the men were paid double a high rate of pay.
I rented three generators. One sat all weekend. Had one of the others failed, the spare set rental would have been paid for in less than an hour in saved wages.
The point is:
I see the primary problem here as 8 men unable to work. My first efforts would be to provide another generator and fix this one at my leisure.
That said, I realize that no-one ever said that life in paradise would be easy, and getting a spare gen-set out to a Caribean island is not always as easy as it is in downtown USA.
I remember having a small diesel set (18 KVA) flown into the moskito coast of Honduras in a small plane. Hand loaded and hand unloaded. The alternative was to send it by costal freighter. It would have been off loaded by hand into a small boat or possibly a dugout canoe for the trip across the bar and across the lagoon to the hospital it was intended for. This was not an insurable risk.
On one of the Bay islands I watched a 60 KVA generator-end being hand loaded into the nose luggage compartment of a small plane. About 5 feet off the ground.
Good luck with your particular site problems.
respectfully

 

[catserveng]

If you can provide a little more detail, I can probably help.

What is the voltage and kW rating of the generator?

Is it PM (permanent magnet) or SE (self excited)? The easy way to tell is look at the VR6, on terminals 26, 28 and 30, do they have seperate leads going to a stator that is NOT the exciter stator? If they are jumpered to 20, 22 and 24 then the unit is self excited.

You said that new diodes just got put on, did they get put on correctly? Older SR4's had six diodes, 3 positive and 3 negative on two seperate heat sinks, with a surge suppressor installed between the heat sinks. Newer SR4's use packaged diodes on a single heat sink, they look like little black blocks of plastic. I have seen the type of failure you are describing when a customer installed the diodes incorrectly, but this is not the only possible cause.

Was the surge suppresor replaced as well?

What was the original fault? Same problem or was the initial problem different?

Have them remove the F1 and F2 wires and measure the resistance, it should be about 3-4 ohms, leave F1 and F2 disconnected, and start and run the unit at rated speed. Measure the voltage at 20, 22 and 24, ( there should be some residual without excitation)and make sure you read the same voltage at the generator terminals, this is to elimnate a sensing problem. Then with it still running check the voltage at 26, 28 and 30, if it is a PM unit this will be about 100 VAC line to line at 240 Hz, if it is an SE unit it will be the same as what you read on 20, 22 and 24.

Make sure the droop circuit is not open, this is at terminals 6 and either 5a or 5 depending on what CT you have.

Make sure the voltage adjust circuit is not open, the remote voltage adjust is at terminals 6a and 7, if there is not a remote voltage adjust connected there must be a jumper across terminals 4 and 7.

I don't have a VR6 manual in an electronic format, but if you go to this link,

http://www.kato-eng.com/usermanuals/351-01057-00, K65-12B & K125-10B.pdf

and download this manual, the KATO K65-12B is essentially the same regulator, except that CAT only uses a 240 VAC sensing version.

There are a number of possible root causes for this type of problem including,

main rotor problem
exciter rotor or stator problem
diode or surge suppresor problems
wiring/connection/assembly issues

If you can provide a little more detail I will check back on this site later today.

 

[waross]

Hi catserveng;
I was hoping you would post in here. Thanks.
I spoke to Bruce in the bahamas and was able to get a little information before we lost the line.
No PMG.
3208 engine.
With battery excitation the main output voltage was good.
There is no sign of heat damage to the sense/power leads.
With the original VR6 the jumper between terminal 24 (sensing?) and terminal 26 (power?) burned off.
With a replacement VR6 the same jumper is burning off.
The set originally worked well for several weeks and then the jumper from 24 to 26 burned off.
The connections on the new VR6 are the same as on the original VR6.
My next suggestion is to check the potential transformers with battery excitation, voltage in and voltage out.
I am open to your suggestions, catserveng.
I get a good confidence feeling talking to Bruce.
With no power on the island, the information here is being relayed to Bruce by a satelite phone, (I understand).
I will check for any suggestions here before I try to call back this afternoon or tomorrow.
If you would like to call Bruce on-site let me know how to send you a phone number.
respectfully

 

[catserveng]

Hello Waross,

Based on your post, it appears he has an overload condition on the power input of the VR6. In the SE configuration with this regulator, there is no current limiting for the power input other than the regulators excitation output limit (which frankly isn't that good). It sounds like the field output is going to ground somewhere, either in the AVR of in the field leads. Did he hook the battery up at the F1 and F2 wires at the AVR?

Have him check F1 and F2 at the AVR to ground with the wires connected and disconnected.

An SR4 that size should pull about 18 VDC and 2-3 amps DC for rated no load voltage, and should be about 30-35 VDC and 6-7 amps DC at full load, input power at 26, 28 and 30 at 240 VAC should only pull about 1-2 amp AC.

I have seen a similar problem that ended up being a sensing lead issue On this size machine, if it is set for 480 VAC, usually has sensing leads coming from the stator to provide the 240 VAC CAT wants for sensing, ther was some load imbalance and as near as we could tell it was trying to equalize thru the AVR's power circuit. Not common but a possiblity.

Have him remove the jumpers between the sensing and the power, run the unit with the battery providing field power and make sure he has sensing on all three phases. Also if he can measure the field current being supplied that may be helpful, since he is likely using the sets or a car battery he may be providing more current then the AVR is capable of.

I am at a military installation today with no phone access, I only get internet because they feel sorry for me sitting here watching a data logger trying to catch an intermittent problem. So I can log in once in a while and check back as long my problem here doesn't crop up.

Sorry I don't have a firm answer, hope that helps.

 

[waross]

After an evenings thought and some time spent looking at the information posted by catserveng I suggest that you look for a ground that may have developed in the system.
First, check the Potential Transformers. These may be torodial and both mounted on a common support. We have not discussed these yet.
You may not have potential transformers.
Some installations use PTs to derive 240 volts from 480 volts,- some installations connect the sensing leads to the winding connections internally.
Please verify that all the leads are free from grounds and that the PTs are in good condition.
Verify that there are no ground faults on the main stator.
You may run without PTs on a six winding (12 lead) generator.
The AVR leads will connect to the 4-7, 5-8, and 6-9 internal connections of the main stator windings to derive 240 volts, rather than to the secondaries of the PTs.
Alternately the Cat PTs may be replaced with a pair of 1000VA lighting transformers in open delta.
It's 9:15 A.M. on the West coast. I just tried phoning Bruce unsuccessfully but I will try to phone throughout the day.
respectfully

 

[catserveng]

CAT 3208 gensets shipped with either VR4 (most common) or VR3 AVR's, if this unit has a VR6 it has been retrofitted at some point, since VR6 came into production in 2004, and the 3208 was discontinued as a genset offering well before that.

Most common for this size unit was 240 single phase sensing and single phase power. There have been a lot of field issues with conversions not done completely or properly causing some real headaches.

Best bet is to get a copy of CAT publication RENR2480, Service Manual for VR6 regulator, it has connection diagrams for all "normal" configurations. Unfortunately CAT doesn't provide these manuals in a transportable electronic format, only in paper and in the dealer SIS (Service Information System).

The KATO manual also has some wiring diagrams, or you can go to the Basler site and download a manual for an AVC63-12 regulator (again, same as the CAT and KATO, different sticker on the front, and Basler and Kato offer more sensing options).

Hope that helps,