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Old 04-12-2007, 14:32   #1
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No Voltage from 6KW Northern Lights Generator

Our boat is back in the water after being in dry layup in Guaymas, Mexico, for six months and we are having a number of problems restarting the 6KW Northern Lights generator. The set is only 3 years old and has 236 hours on it.
After jump starting the engine to compensate for a dead starting battery, it ran for a few minutes before shutting down on high temp. Troubleshooting the cooling system revealed a burned up sea water pump. After replacing that, the engine runs fine but the generator puts out only 30 VDC instead of the desired 240 VAC.

All connections in the Automatic Voltage Regulator are tight and free of corrosion. Resistances of windings are a little high compared to those specified in the operator's manual but were not totally out of line.

Resistance through all fuses and breakers show 0 ohms when closed and >20 megohms when open.

Field flash voltage, which is applied with the preheater switch, reads 14V DC across the DC breaker on the regulator front panel. There is no value specified for this in the Manual but I assume that 14V is adequate.

I removed, mechanically agitated, and reinstalled all relays in the control box (labeled SR, RR, SDR, and PR). These relays do not show up on any wiring diagram so I can't tell how they affect operation of the machine. I do not have ready access to a relay tester here in San Carlos but may be able to find one or just buy a new set of relays at the local Auto Zone store. Before I go to that expense and trouble though, I would like to know if failure of one of those relays could cause the symptoms I'm seeing or if there is something else I can check.
Has anyone had similar problems or know what to check next? I'll be glad to send resistance values to anyone who needs them to help analyze this problem.
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Old 04-12-2007, 15:18   #2
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Did you go through the troubleshooting checklist in the owners and the installation manual? Have you called Northern Lights support line?

I could not find their support number but I did find their number for their corporate offices at 1 800 762-0165
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Old 04-12-2007, 15:30   #3
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This thing isn't an "Inverter generator" is it?

30DC sounds kinda weird coming off an AC circuit. Sounds like some bad diodes or a funky regulator. It will be interesting to see what Northern Lights comes up with. I'll bet that it's something simple.

You didn't mess with any of the wiring on your circuit panel did you? Maybe reversed polarity somewhere.

Keep us posted, will ya.
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Old 04-12-2007, 20:07   #4
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When you jumped started the thing, did you leave the good battery connected as well?? If you removed the good battery, then there maybe a relay/s not being energised due to a flat battery. It's just a long shot, but......
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Old 04-12-2007, 21:15   #5
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Yachtsman Dream Guaymas

Hi,
Sorry to get off the subject. I hope it is a simple fix.
I have been trying to get some info about the haul out facility in Guaymas. I have a 47' cat with 27' beam and was wondering if they can haul it out and I was also wondering if they had dry storage in a secure place? It sounds like they do? Could you fill me in after you get your problem figured out.
Thanks so Much,
Gary
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Old 04-12-2007, 23:29   #6
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OOPS - Meter Misuse

Forget the part in my original post about the 30 VDC output - I had the digital multimeter in the wrong mode. As it looks now, the generator was never really the problem at all. See my status report at the end of this post for details.

Here are replies to several other posts. Thanks to all for your input.

David M: Yes I looked through the troublshooting checklist but it said nothing about loss of output voltage. I have not yet contacted Northern Lights but have talked to an employee of Hatton Marine in Seattle, a factory authorized service center. He told me he was the design
engineer for that generator. More on conversations with him in the status report below.

Kanani: See above for explanation of 30 VDC. I did not change any wiring in the control box except to disconnect one multiconductor connector and pull one lead off the DC circuit breaker at separate times. The connector only goes together one way so I couldn't have messed that up.
Because I only had only one wire off the circuit breaker at a time, I feel confident I didn't screw that one up either.

Alan: I disconnected the good battery and let the generator run for about an hour to recharge its dedicated Trojan starting battery. Since then it has started the engine several times and seems to be holding its charge quite well.

Quartersplash: The haulout facility in Guaymas uses the 300 ton TravelLift at the shrimp boat yard across the street until they dredge a channel to their own smaller lift ways. The storage yard owner has plans to put in a ramp to haul out multi-hulls by trailer but judging from the rate of progress on dredging, I wouldn't expect to see a ramp in operation for another year or two. Unfortunately for you, the ways at the shrimp boat yard are only 25 feet wide (I measured with a tape measure before my haul out last spring). The dry storage is semi-secure in that there is a cyclone fence around the yard with a gate that is never locked but is usually swung
closed and occasionally guarded by yard workers. The yard itself is a dirt lot. There are really run down head and shower facilities sharing the building in the center of the yard with the office and a tool room. Next to that building are some old fish oil tanks that appear to be constantly leaking or overflowing. The good news is that living aboard is permitted and the rates are really low. See their web site (marinasecaguaymas.com) for more details and pictures.

Current Status:
The engineer I talked to recommended cleaning the slip rings under the field excitation brushes then starting the generator and measuring its output voltage. If it had not built up quickly, I would have had to flash the field as this particular machine has no separate field flash circuitry, contrary to indications in the owner's manual.

Initially I did not want to inspect the slip rings because that end of the generator is only a few inches from the aft end of the engine room and the sound shield on that end of the machine has several hoses and cables through it that prevent it from being lifted out. Working left handed with a mirror, I was finally able to clean the slip rings until they were shiny again (wish I'd had a rubber arm for that task!).

After starting the machine again, I measured the voltage at the main output terminals with two separate meters on the correct scale this time and saw 242 VAC as expected. Unfortunately, when I closed the main distribution breaker on the output of the generator, voltage dropped instantly to zero. When I reopened the breaker, voltage came back up. I called these results in to the engineer in Seattle who then informed me that there must be a direct short across the output that causes the field in the generator to collapse.

Tomorrow I'll rip into the distribution breaker to see if there is a smoking gun (or varmint) there. I'll post another follow up with my findings and hopefully final resolution after that phase of the investigation. Meanwhile I'm charging our house batteries with solar panels supplemented by main engine as necessary every few days.
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Old 05-12-2007, 01:01   #7
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Hmmm, tricky one. Does the engine labour when you close that breaker? That would tell you if there was a short or not. And besides, wouldn't the breaker trip?? I am thinking you may still have an issue with the slipring department. If the rings were corroded enough to stop voltage, what about the brushes that run on the slip rings. They may still be dirty. There may be just enough contact to allow the voltage to pass, but when the load is applied, the current simply can not be transfered across. If that is not the source of the problem, it will most likely be a connection anywhere along that circuit. Look at all connections and terminations along that line.
A test load is kinda needed. Something like a 75W bulb with a length of wire and a clip to attach to one part of the circuit and a length of wire and a probe. That way you can check variouse points along the way and see at which point the bulb lights and which point it does not.
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Old 05-12-2007, 02:03   #8
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I agree with Alan. The problem with testing with no load is that a high input impedance meter like a digital(10 Megs or more)only needs a potential. A high resistant junction can cause the problem. Allowing a voltage reading without being able to produce any current. As soon as a load is applied the total voltage is dropped across the resistive junction.
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Old 05-12-2007, 21:14   #9
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Problem Solved


Turns out the problem was not with the generator after all but with a dead short across the input wires of a 240/120 volt transformer connected to the load side of the generator main output breaker. It was an easy problem to fix but a bugger to figure out. Thanks to all who contributed suggestions here and especially to Greg at Hatton Marine in Seattle who kept telling me that there must be a dead short across the output of the machine that collapsed the field in the generator. What surprised me was that neither of the two breakers in line to the transformer tripped.

The scenario as I pieced it together went something like this:
A wire connector on one input to the transformer worked its way into contact with the other input wire, shorting the input to the transformer and also the output of the generator. When I first started the generator, that dead short collapsed the generator field so the voltmeter in the system read near zero. Because I saw no output from the machine, I immediately assumed that the problem was with the generator and not downstream loads. Once I verified that the machine produced voltage at its output terminals, and could support a 240 volt load (air conditioning air handler) it was a relatively simple matter of disconnecting loads one at a time, measuring lead to lead resistance, and isolating the culprit.

Because a transformer is such a simple device, I didn't think it likely to fail. Thus I did not focus on that early on as a possible cause of the problem. Neither did I expect a dead short across the output of the generator to collapse its field without tripping a breaker anywhere in the system. These were some valuable lessons to learn. I'll post a picture in this thread later when I get a more reliable internet connection - the uploading process keeps timing out here.

Thanks again for all your support. You guys are the greatest!
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Old 06-12-2007, 00:16   #10
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A transformer fault is common and should always be a suspect. The breaker not tripping is a concern. Check you have the correct rated breaker. When the feild collapses, there is no current flowing and so the breaker will not trip. But for a very short instance, the current should spike and then collapse. So the breaker must operate fast enough to trip before the feild collapses. A breaker that uses a bimetal element will not switch fast enough to be any good. You need to get a fast acting breaker.
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Old 06-12-2007, 04:50   #11
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Quote:
Originally Posted by Alan Wheeler View Post
...the breaker must operate fast enough to trip before the feild collapses. A breaker that uses a bimetal element will not switch fast enough to be any good. You need to get a fast acting breaker.
Any short circuit should open any circuit breaker under "Instantaneous Trip” conditions.

A high quality thermal circuit breaker will open a 10,000 ampere fault (at 250 volts AC) in about 40 or 50 milliseconds;
whereas a magnetic (or thermal-magnetic, or hydraulic-magnetic) breaker will open a similar fault in about 10 milliseconds.
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Old 20-12-2007, 17:38   #12
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Final Wrap Up

In my last reply here I promised to upload a picture when I had a better internet signal. I went one better and posted on my web site the entire story of how I broke, then fixed, then broke, then finally fixed my generator. The URL of that story is: Gen Set Troubleshooting Log

Any comments are welcome. I compiled this story for others out there who might some day encounter similar problems as well as for my own history.
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Old 20-12-2007, 18:04   #13
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Comment.........OK,

The motor has now been overheated three (i think) times so some of the life may have been taken out of it.

Good job on figuring it all out though!!

The money saved DIY will more than make up for loss of longevity - if it really lost any.
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