alternator fires

[stinkpots]

I had an alternator fire last year.
I have twin inboard Gardner diesels in a sound insulated engine room. I was charging using one engine with the alternator at max output of 100 amps. I was on deck and heard the engine note change. I went below to check and on opening engine room door I was presented with a lot of smoke and a horrible noise. It turned out that the 150 amp BEP breaker just before the battery had failed and went open circuit. I have now replaced it with a 150 amp slow blow fuse. The alternator as well as the external regulator were both toast.
An expensive failure caused by a component that was supposed to protect not destroy!
After shutting down the engine and isolating the batteries the alternator eventually cooled down without the need for fire fighting. It was glowing hot for a while and producing a lot of smoke.

[SOLAR SUPPORT]

Originally Posted by Journeyman

Does anyone have any anecdotes about alternators literally burning up?

I have heard of one recently and was unaware of the potential danger, particularly with high output alternators.

Also, I have thought of alternator faults as most likely self limiting, but a short to ground in a running alternator I guess is basically an arc welder capable of starting a hard to put out Metal Fire:

https://www.wtamu.edu/~cbaird/sq/mob...t-metals-burn/

The possibility of burning the alternator is higher than expected. My alternator was heating up to 135°C while charging with 60% of its capacity. You can easily measure this with a tool with a laser probe. If the engine speed is kept at low or idle level during battery charging, the alternator cannot cool itself sufficiently at 50% and higher loads. Its temperature rises constantly and It can overheat and burn after a while. Especially if it works with lifepo4 technology, since the alternator will have to work at full capacity all the time, it must be protected by taking additional precautions.

[boatpoker]

I have experienced an alternator melt down.

Here is such a common recommendation from my survey reports that I have it on autotext ...

"No fuse protection was found on any of the batteries. ABYC "Storage Batteries" Standard E-11 and TP1332E require in part requires positive conductors be fuse protected within 7” of the battery or 40” if the conductor is fully enclosed with the exception of conductors running to engine starter motors. It is the surveyor’s opinion that this standard is inadequate and that all positive conductors should be so protected."

[dfelsent]

I had an alternator failure. It was a Balmar. The windings became so hot they charred black. No flames that I saw.
Sure smelled like fire though. Unnerving.
Shut the engine down, dropped the hook as I was in Boston inner harbor.
Fortunately it was the second alternator so I could electrically and mechanically disconnect it and still run the water pump">raw water pump and have some charging.
The diodes were fried.
My experience with failed motors and transformers, both of which are wound with enameled wire for the most part, is that the enamel won’t support much if any of a flame.
An arc is a different beast entirely.

[Wotname]

Originally Posted by stinkpots

I had an alternator fire last year.
I have twin inboard Gardner diesels in a sound insulated engine room. I was charging using one engine with the alternator at max output of 100 amps. I was on deck and heard the engine note change. I went below to check and on opening engine room door I was presented with a lot of smoke and a horrible noise. It turned out that the 150 amp BEP breaker just before the battery had failed and went open circuit. I have now replaced it with a 150 amp slow blow fuse. The alternator as well as the external regulator were both toast.
An expensive failure caused by a component that was supposed to protect not destroy!
After shutting down the engine and isolating the batteries the alternator eventually cooled down without the need for fire fighting. It was glowing hot for a while and producing a lot of smoke.

Hmm... I am wondering how the circuit breaker tripping (going open circuit) caused an alternator fire.

To my mind, an alternator fault is more likely to cause the circuit breaker to trip rather than vice versa; the circuit breaker was the result of an alternator fault, not the cause of it.

Not saying it didn't happen as you have described it, rather it would be an unusual case.

[Dieseldude]

Originally Posted by Dave9111

quote:

Commercial generators, motors, and transformers are tested annually for insulation weakness. This is commonly called "megger testing". It requires a special resistance meter with internal high voltage source to test for high resistance that a regular ohm meter will not reliably measure. The test is looking for any high resistance partial shorts between windings, and between each winding and case ground. This would require disconnection of the diodes and regulator to avoid destroying them with high voltage. After testing, windings must be shorted momentarily to bleed off any stored charge due to capacitance effect. The test instrument is not cheap, but it can be used for testing other devices.

end quote:



Where does this happen annually ?? Certainly not in the USA!!

By class society and port state rules, commercial vessels are required to do insulation testing annually. If they do not, they are not permitted to sail, and may not qualify for insurance. I know because as an engineer, I have both done it, and have watched contract electricians do the job.


If US registered vessels are getting away without annual insulation testing, it is an exception to rules imposed by most port states.

[sailingharry]

I have a pair of PowerLine alternators, 150 and 120. The 120 has an "issue" and only puts out 70A, so it's rather tame (to be fixed this winter).

The 150 puts out 140, for over an hour. It's a beast. And like all alternators, the output terminal is a steel stud. This stud is an actual conductor, with resistance about 10 times that of copper. It gets H-O-T! The case itself runs about 200F, maybe a bit more. The copper coils are quite black -- going back for a rebuild and I need to dig into the regulator temp sensor.

But the punch line. That steel stud? Connected to a 2/0 power wire (and same size ground wire, and proper fusing). This is what I noticed one day on morning engine checks. OUCH! I really wish there were a way to make that steel stud out of something conductive, like, say, copper!

[SOLAR SUPPORT]

In order to work safely, all electrically operated tools must first be designed to be protected from external factors that may harm them. An alternator should be able to reduce the working load on it before it burns by overheating, or it should be able to take a short break from the energy it produces and cool itself. It's not too difficult to do this with a simple thermostat.

[sailingharry]

Originally Posted by Dieseldude

By class society and port state rules, commercial vessels are required to do insulation testing annually. If they do not, they are not permitted to sail, and may not qualify for insurance. I know because as an engineer, I have both done it, and have watched contract electricians do the job.


If US registered vessels are getting away without annual insulation testing, it is an exception to rules imposed by most port states.

In the US (and I suspect "most port states") see a very big difference between pleasure vessels and inspected commercial vessels.


This site is mostly concerned with privately owned pleasure vessels.


In the US, at least, there are zero mandatory inspections of any sort (by officials or licensed/accredited inspectors) and spot inspections by random boarding, as well as scheduled inspections by insurance carriers are far less rigorous than any commercial requirements (boardings focus on easily identified safety items like flares and PFDs, and insurance surveys are mostly checklist visual inspections with no specialized equipment like infrared cameras or meggers).

[dmkkeng]

I recently had an alternator fire, it charred the internal windings and positive connection to the alternator. I was at the helm and noticed the burning smell. We immediately shut down the engine and put up the sails. My smoke detector is located at the entrance of the forward cabin, it did not go off. I now have a 2nd smoke detector located closer to the engine room. Perhaps it would be better to locate the smoke detector in the engine room however it would likely be prone to false alarms and it might not be loud enough to hear above the engine noise. I have an external regulator wirh a temperature sensor installed on the batteries, to my knowledge there is no option for a temperature sensor to be installed on the alternator. If available I think that would be an option worth considering. Both my start and house batteries are fused. This fuse did not blow however they are there to prevent the wire harness from starting a fire due to a short somewhere in the electrical system. I believe in my situation the alternator simply overheated, the case while significantly hot, did not ignite. I have since disconnected the external regulator as I believe it is running the alternator to close to its maximum capacity. The external regulator would run my 80 amp alternator at 70+ amps, the internal regular appears to peak around 55 amps.

[Dieseldude]

Originally Posted by sailingharry

In the US (and I suspect "most port states") see a very big difference between pleasure vessels and inspected commercial vessels.


This site is mostly concerned with privately owned pleasure vessels.


In the US, at least, there are zero mandatory inspections of any sort (by officials or licensed/accredited inspectors) and spot inspections by random boarding, as well as scheduled inspections by insurance carriers are far less rigorous than any commercial requirements (boardings focus on easily identified safety items like flares and PFDs, and insurance surveys are mostly checklist visual inspections with no specialized equipment like infrared cameras or meggers).

Yes. agreed, about scope of this site, and different standards for commercial and private vessels. Was just pointing out the value of an insulation or "megger" test for alternators and other electrical equipment. Going beyond minimum standards in maintenance can avoid serious trouble. Being that an alternator can be subject to high temperatures, windings are vulnerable to insulation break down. They are open vented, vulnerable to fuel or coolant leak damage too. A lower cost insulation tester can be had for about $150. This, and a small investment of time to learn how to use it can pay off big. https://www.amazon.com/Klein-Tools-E...0976256&sr=8-3

[SOLAR SUPPORT]

Alternators operating in a closed and insulated room on boats overheat in a short time even when operating at 50-60% of their capacity. The insulation coating on the stator windings of the alternator is damaged at temperatures up to 120~130 C°. If the engine runs at low speed, this situation leads to the burning of the winding insulation in the alternator, more specifically. If the alternator regulator is located outside the alternator, temporarily resetting the load of the alternator with a simple thermostat, thus allowing the alternator to cool itself while running at idle, will prevent the alternator from overheating and burning under load.

[goboatingnow]

Originally Posted by SOLAR SUPPORT

In order to work safely, all electrically operated tools must first be designed to be protected from external factors that may harm them. An alternator should be able to reduce the working load on it before it burns by overheating, or it should be able to take a short break from the energy it produces and cool itself. It's not too difficult to do this with a simple thermostat.

What should be on a boat is very different to what IS on a boat.

When you think of the cost of a new yacht the lack of engine and systems monitoring is ridiculous. The use of stock car regulators designed for entirely different situations should never be allowed in boat alternators but sadly they are.