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Author Topic: 7.5 st head update  (Read 2389 times)

32 coupe

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7.5 st head update
« on: November 05, 2017, 02:14:35 PM »
About a year later further testing on my 7.5 head reveals more problems.

It came with the 115 avr.  When I received it it had a bad imbalance growl so I tore it down,
found loose mounting problems on some of the coils. Repaired that as well as a good spray down
with the red varnish sealer.

More testing has shown that a 10 amp load on 1 leg (115 volt) it still has a pretty nasty growl.
The avr will run away on the unregulated leg. 90 and 170 or more.

Thinking I would remove the avr and rectify the problem. Wrong ! With the avr out the output is a
nice 325 volts !

I guess I will either look for a 220 to 110 transformer or order the 220 volt regulator.

Glad I ordered a 15kw and a 7.5 kw years ago when they were better quality. 

Sad.

Metro 6/1 turning a ST 7.5 KW gen head
Changfa 1115 turning a ST 15 KW gen head
Ashwamegh 2/25
John Deere 110 TBL
New Holland TC 30

"I was sitting here reading this thinking what an idiot you are until I realized it was one of my earlier posts !"

32 coupe

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Re: 7.5 st head update
« Reply #1 on: November 06, 2017, 09:40:43 PM »
Just to keep everyone updated:

I spoke with Tom today and he is sending a 240 avr
to see if it will correct the problem.

I will post results after it arrives and further testing.

Gary



Metro 6/1 turning a ST 7.5 KW gen head
Changfa 1115 turning a ST 15 KW gen head
Ashwamegh 2/25
John Deere 110 TBL
New Holland TC 30

"I was sitting here reading this thinking what an idiot you are until I realized it was one of my earlier posts !"

cujet

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Re: 7.5 st head update
« Reply #2 on: November 08, 2017, 04:17:16 PM »
I had one heck of a battle with my ST head. George hooked me up with the right way to manage the issues.

If I were to do it over, I'm not at all sure I'd purchase an ST head. Even the Harbor Freight 10KW head is higher quality.
People who count on their fingers should maintain a discreet silence

32 coupe

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Re: 7.5 st head update
« Reply #3 on: November 08, 2017, 09:34:11 PM »

I am thinking the "Stamford" clone is probibly the way to go.

The cost is definitely a factor.

The thing that gets me is the fact that my "older" st heads work so well.

Gary

Metro 6/1 turning a ST 7.5 KW gen head
Changfa 1115 turning a ST 15 KW gen head
Ashwamegh 2/25
John Deere 110 TBL
New Holland TC 30

"I was sitting here reading this thinking what an idiot you are until I realized it was one of my earlier posts !"

glort

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Re: 7.5 st head update
« Reply #4 on: November 08, 2017, 11:41:20 PM »

I am thinking of getting a 10 or 20Kw 3 phase head.

Import it direct seeing  can't find ANYONE here who has them.
Are the latest ones any better or should I forget about them?  I want something I can hook up and use. Bit over pulling shit apart and rebuilding it just to make it work atm. Far too much else to do without buying any new work.

32 coupe

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Re: 7.5 st head update
« Reply #5 on: November 09, 2017, 12:54:18 AM »
Glort,

Many here would not recommend the st heads..

My 2 older units are great. They don't have avr's and maintain voltage and frequency very well.
I have never put an oscope on them so I don't know what the signwave looks like but they run
everything in my home and shop just fine.

Bruce had a write up about his latest st head that had aluminium wire and its poor performance.
I took mine apart to repair some problems and spraycoat it but can't say if it was aluminium or
copper (it looked like copper but I didn't scrape test it) but will say the tie connections were
soldered and without the "crimp" connections.

I am seriously thinking the "samford clone" is the way to go. The cost is about double what the
st units go for but I agree with your assessment of not wanting to "rebuild" a new unit.

Gary




« Last Edit: November 09, 2017, 01:01:38 AM by 32 coupe »
Metro 6/1 turning a ST 7.5 KW gen head
Changfa 1115 turning a ST 15 KW gen head
Ashwamegh 2/25
John Deere 110 TBL
New Holland TC 30

"I was sitting here reading this thinking what an idiot you are until I realized it was one of my earlier posts !"

38ac

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Re: 7.5 st head update
« Reply #6 on: November 09, 2017, 11:49:33 AM »
I have 5KW and 15KW STs from Tom 8-10 years ago that have been very good but admittedly not may hours on them, 500 or so.  I bought a couple spares later on but they are still in the crates. Guess I better get them out and spin them up? sounds like they could be boat anchors.
« Last Edit: November 09, 2017, 11:54:37 AM by 38ac »
Collector and horder of about anything diesel

glort

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Re: 7.5 st head update
« Reply #7 on: November 09, 2017, 12:48:34 PM »

Looking on the ali website, there's not that much difference between the brushless Stamfords and the St's.
All 3 phase:

22KW Stamford, $835 Aud
20 Kw STC   $691

30 Kw Stamford   $877
30 Kw STC   $918

Yes, double checked that, both 30 KW 3 phase. Stamford is cheaper, same company.

A little 6.5Kw stamford however is $691
For my money, I'll take the bigger one which would have more mass and therefore reactive stability and would be under stressed all the time.
As well as run the whole house AC and oven at the same time inc.

Take it this is the Stamford type preferred?

https://www.aliexpress.com/item/KD184G-30KW-37-5KVA-Stamford-AC-Synchronous-Brushless-Alternator-by-sea/32617815935.html?spm=2114.search0104.3.37.UGe9ey&ws_ab_test=searchweb0_0,searchweb201602_3_10152_10065_10151_10130_10068_10344_10345_10547_10342_10343_10340_10341_10548_10541_10307_5670020_10060_10131_10155_10132_10133_10154_10056_10055_10539_10537_10059_10536_10534_10533_100031_10103_10102_10107_10142_10562_10084_10563_10083_10561_10566_5740016_10564_10565_5650020_10175_10312_10313_10314_5660020_10550_10073_10551_10552_10553_10554_10557,searchweb201603_1,ppcSwitch_5&btsid=d2e19598-8773-45fa-bcca-4a2fa94ac4e7&algo_expid=831b4a4f-374d-49ca-8700-b1814376df42-5&algo_pvid=831b4a4f-374d-49ca-8700-b1814376df42

BruceM

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Re: 7.5 st head update
« Reply #8 on: November 09, 2017, 04:00:07 PM »
While I hate to defend ST's at this point, I would add that the 3 phase versions have never shown the waveform distortions of the single phase units.  I also don't think we have enough data on the large ST's (10KW+)  to condemn them as well but it does not encourage confidence if they are made by the same manufacturer, with the same crap bearings, castings, diodes, poor tolerances, etc.


32 coupe

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Re: 7.5 st head update
« Reply #9 on: November 09, 2017, 07:27:25 PM »
When I spoke with Tom he says now all his units are copper wound and from a different vendor.

Metro 6/1 turning a ST 7.5 KW gen head
Changfa 1115 turning a ST 15 KW gen head
Ashwamegh 2/25
John Deere 110 TBL
New Holland TC 30

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BruceM

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Re: 7.5 st head update
« Reply #10 on: November 09, 2017, 08:48:25 PM »
Tom of CGG is very personable, but he's technically quite limited and is still shipping units where the harmonic windings are NOT right, and often with a 120V AVR which then causes growling imbalance problems.  He may have changed vendors again, but frankly, I suspect he's still going primarily low bid or he wouldn't be accepting or selling such poor quality product.  He's also shipping units with cracked cases at least on arrival; poor castings or materials.

Having the stock harmonic regulation was an important part of choosing an ST for many of us... I build it into my "manual reversion mode".   Regardless of any other type of electronics failure, it gives you something you can count on.  You're not getting that when you buy them now-  and not with some in the past, either.  It's Rajkot roulette all over again.






32 coupe

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Re: 7.5 st head update
« Reply #11 on: November 09, 2017, 10:55:47 PM »

Bruce,
You have mentioned the st 3 phase heads on more than 1 occasion.

I have spent some time looking but am unable to locate any. Any links ?

I will add that unless I am able to locate the 3 phase st type my future
purchase will be the "stamford clone" unit.

Gary

Metro 6/1 turning a ST 7.5 KW gen head
Changfa 1115 turning a ST 15 KW gen head
Ashwamegh 2/25
John Deere 110 TBL
New Holland TC 30

"I was sitting here reading this thinking what an idiot you are until I realized it was one of my earlier posts !"

BruceM

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Re: 7.5 st head update
« Reply #12 on: November 09, 2017, 11:17:37 PM »
Odd, I can't find any 3 phase ST's online either. 

glort

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Re: 7.5 st head update
« Reply #13 on: November 10, 2017, 03:58:58 AM »
Odd, I can't find any 3 phase ST's online either.

How many you want?  :0)

A little one:

https://www.aliexpress.com/store/product/STC-5KW-3-Phase-Brush-5KW-Alternator-Generator/417895_32298903573.html?spm=2114.12010612.0.0.37d96bffY7Elc7


A decent one:

https://www.aliexpress.com/store/product/STC-20KW-3-phase-Brush-20KW-Alternator/417895_918156773.html?spm=2114.12010612.0.0.71a27f13RStHRV

One to run the average American RV:

https://www.aliexpress.com/store/product/STC-50KW-AC-Three-Phase-Brush-Diesel-Alternator-by-sea-ON-SALE/417895_32615162420.html?spm=2114.12010612.0.0.3186de35aSkFWG

Now.... Were those stamfords the ones you were all talking about that are supposed to be better?
What are the advantages apart from better build quality ( supposedly?)
Brushless and..... ?

If they have decent advantages, to me they wold be worth ponying up the extra and not having to worry about them.


glort

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Re: 7.5 st head update
« Reply #14 on: November 10, 2017, 04:27:14 AM »

For the rest of the world that can have such dangerous and lethal things as diesel engines.....

Might be worth getting the whole setup Alternator and engine all hooked up ready to go.   
Supposedly.....

https://www.aliexpress.com/store/product/GF1-10KW-Diesel-Generator-Set-12-5KVA-Power-Generation/417895_32297961485.html?spm=2114.12010612.0.0.52dd424dKKjtsW