Author Topic: CGG ST heads- warning- aluminum windings  (Read 7201 times)

dieselgman

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Re: CGG ST heads- warning- aluminum windings
« Reply #15 on: October 08, 2016, 10:52:00 AM »
I have less experience with the Chinese stuff, but have long worked with the (once) American made Marathon heads and others. We have had quite a number of them repaired and rewound over the years, usually by specialty winding shops with all the tricks/tools/and expertise. The LIMA MAC variety is one that is brushless and "inherently regulated"... does not require anything other than its own residual magnetism and very precise winding specs to maintain its voltage within 5% under almost all conditions including minor overloads. We have seen occasional rewind failures due to off-spec wire where the output voltages would be off significantly with only a slight, almost imperceptible, change in the wiring used. We have also seen struggles with some of the Italian heads which apparently used a metric wire size and correct outputs could not be achieved nor properly maintained when rewound with conventional North American available wiring stocks. This is from work done by well seasoned winding professionals who were quite well versed with all the technicalities and nuances.

More recently we have received a large quantity of Chinese ST heads specified, marked, (and supposedly pre-tested) for 60Hz 120/240 operation. Unregulated these heads are producing closer to 300vac at 1800rpm. Tom at CGG confirms that many of his do exactly the same thing out of the box and need a regulator or rheostat to bring them into spec. This may just be the norm with the ST variety of Chinese heads in current production.

With the reported under-voltage stuff and our recent experiences with the ST overvoltage, I am led to believe that manufacturing expertise and conformance to precise specifications may be quite lacking in much of the Chinese stuff. This may have nothing at all to do with the one noted case of sub-standard aluminum windings but rather be more to do with loose or variable manufacturing tolerances. Sound familiar? Like something out of Rajkot? I think it is the same syndrome of immediate money vs quality control - very shortsighted and foolish in my own worldview.

dieselgman
« Last Edit: October 08, 2016, 11:02:37 AM by dieselgman »
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cujet

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Re: CGG ST heads- warning- aluminum windings
« Reply #16 on: September 11, 2017, 12:09:48 AM »

With the reported under-voltage stuff and our recent experiences with the ST overvoltage, I am led to believe that manufacturing expertise and conformance to precise specifications may be quite lacking in much of the Chinese stuff. This may have nothing at all to do with the one noted case of sub-standard aluminum windings but rather be more to do with loose or variable manufacturing tolerances. Sound familiar? Like something out of Rajkot? I think it is the same syndrome of immediate money vs quality control - very shortsighted and foolish in my own worldview.

dieselgman

Bumping up an old thread, to agree with Dieselgman. I work on some of the finest aircraft mankind has ever produced (The Gulfstream G650ER) and the Listeroid/ST situation is an exercise in frustration. I think they can be viable methods of making power. But it does take some effort and know-how.

My ST head seems to have copper wire.
I give up

rosebud

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Re: CGG ST heads- warning- aluminum windings
« Reply #17 on: September 16, 2017, 11:22:55 PM »
I have 3kw st head as well....

Today I found it has aluminum wire... oh joy..

I had redone the rotor winding connections last year.. and ran it for ~10 hours after a winter power outage... all good.
A month ago, I started up the 6/1 to test things.. and no power on the st head.

Wish I had picked up on the aluminum last year.. not too swift...

Next step... get a 2 pole for power backup... rewind the rotor with copper at leisure..? or go for a pricey 4 pole head with better reliability?

this is a hobby ... right..

regards,
steve
Listeroid 6/1
SL1...4.25hp
ST 3kw
1.6kw PV

BruceM

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Re: CGG ST heads- warning- aluminum windings
« Reply #18 on: September 17, 2017, 12:27:32 AM »
Check your resistance on the rotor windings from the slip rings. If it's open circuit, then check/recrimp the connections again.

My neighbor's ST-3 had one rotor wiring go open within a couple hundred hours of use- and it was not at the connectors.  It appeared to be an invisible flaw in the aluminum wire internally; there was no break.






rosebud

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Re: CGG ST heads- warning- aluminum windings
« Reply #19 on: September 18, 2017, 02:08:44 AM »
I did have a look a the resistance at the slip rings... per Utter Power's trouble shooting guide... I saw something in the range of 20Mohm's .... way over the suggested 17ohm.

Proceeded to open the individual connections, to see where the problem was...  and noticed white powder coming out of one of my crimp connections... that's when I tweaked on the aluminum windings. This wire is very soft/brittle.. getting shorter so will have to splice in some pieces to make future connections/repairs.

This is a learning experience, but part of the fun... electricity is kinda magic stuff

thanks for the advice,
steve
Listeroid 6/1
SL1...4.25hp
ST 3kw
1.6kw PV

rosebud

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Re: CGG ST heads- warning- aluminum windings
« Reply #20 on: September 29, 2017, 03:33:04 PM »
update...

I soldered up all the connections on the rotor. Used Uniweld 4300 kit... it worked. Aluminum is not nice to work with... especially with the wires getting shorter.. lots of solders.
See how long things last? .. my soldering may not be long term reliable... original wire is fragile...

I am getting ~7 ohms across each coil and ~27 ohms in total.. at the slip rings.

Just re installed the st head and cranked up the 6/1... there is power... tested it to 1500w.
Plan to get a 3600rpm head .. as back up.

onward,
steve
Listeroid 6/1
SL1...4.25hp
ST 3kw
1.6kw PV

BruceM

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Re: CGG ST heads- warning- aluminum windings
« Reply #21 on: September 29, 2017, 03:43:07 PM »
Thanks for the tip on the Uniweld 4300!  While not ideal, sometimes we must cope with aluminum connections. The biggest bugger is making copper to aluminum connections...did you find something for that as well?

rosebud

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Re: CGG ST heads- warning- aluminum windings
« Reply #22 on: September 29, 2017, 08:50:35 PM »
Last year I had the rotor out and used copper "jumpers" to make up for the shortened ends on the aluminum wire.. it breaks very easily.
At that time I had a couple bad crimp joints.... fixed per Utterpowers recommendations....generally.
Sadly... I did not notice that I was working with aluminum ... thought it was poor quality copper. Never entered my head it was not copper.

Same problem this summer... then the aluminum mystery unfolded... or revelation. (white powder at crimps)

I stayed with aluminum for the repair. Picked up a bit of aluminum at Princess Auto.. similar to HF in US. Hard stuff to find in this area.
The aluminum wire was the same gauge, but much stiffer.

It is a tedious repair and I am not a competent solder type.. but learning is part of the fun.

The Uniweld product is supposed to join copper and aluminum.. think it will.. the flux is effective stuff.
I suspect it is not good for copper and aluminum to touch... corrosion and such.. (experts can weigh in on this)

If you want to join copper and aluminum .. suggest try using a butt connector (stainless), with an anti oxygen paste. Again keep copper from touching aluminum.
I did not have much room left for this connection, had to lengthen the wires from the coils anyway.
Have to think a bit about centrifugal force.. with butt connectors, as well... more stuff spinning in there...forces on ~17awg aluminum wire.

I'm not pretending to be a sage, just rambling per my path (so far) on this repair... hope it helps someone.

regards,
steve
Listeroid 6/1
SL1...4.25hp
ST 3kw
1.6kw PV

BruceM

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Re: CGG ST heads- warning- aluminum windings
« Reply #23 on: September 29, 2017, 09:47:04 PM »
I'm an utter novice on working with aluminum wire myself, thanks for sharing your experience. There are some very spendy special crimp connectors for aluminum-copper, but I've never used them.




glort

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Re: CGG ST heads- warning- aluminum windings
« Reply #24 on: September 30, 2017, 12:13:49 AM »

Is it all financially viable to have these units rewound in Copper?

As well as getting rid of the aluminum it would seem that a first world rewind job would probably make for much better output wave forms and cure other common ill's with these machines.

I have never had a motor rewound so no Idea of cost but just pondering. Don't expect it would be cheap but if it puts these machines on par with the more expensive heads could be worth it.

mike90045

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Re: CGG ST heads- warning- aluminum windings
« Reply #25 on: September 30, 2017, 12:52:58 AM »
I too, was going to ask about the rewind option vs repairing the repairs.   During rewind, can they skew the windings to improve the waveform. or does that require a total redo of the laminations ?? I've only had mine apart far enough to replace the bearings.

broncodriver99

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Re: CGG ST heads- warning- aluminum windings
« Reply #26 on: September 30, 2017, 01:31:26 AM »
I don't have any experience with an ST head but just priced rewinding a 5 HP 3 phase motor and it was $550. New motor was around $875.

dieselgman

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Re: CGG ST heads- warning- aluminum windings
« Reply #27 on: September 30, 2017, 04:51:35 AM »
Typical cost of $500 to rewind a stator... obviously not normally viable on a $500 genhead.

On the issue of dissimilar metals and corrosion... if you can exclude oxygen from the connection, resistance through the connection will usually remain OK. We use a grease-like product in all such connections in building electrical systems. There are sometimes aluminum/copper interfaces to deal with, they will always build up oxidation (and resistance) if left exposed.

dieselgman
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