Lister Engine Forum
How to / DIY => Everything else => Topic started by: tyssniffen on July 06, 2015, 05:01:22 PM
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took me a while to even realize it wasn't the power tool that quit. I'm just posting here because I need some ideas on what to look for after a first check for loose wires and finding none.
I was running a big old table saw (on 120ac) when suddenly no power... well, after checking, I see that the alt is putting out about 8volts with the engine speed the same as ever, belt still tight..
nothing seems to be loose or disconnected (and how would it put out ANY volts if something wasn't connected?) so I'm already scratching a well-scratched head.
would anyone know where I could find detailed photos of what all the wiring looks like on one of these chinese ST 3k alts?
Tys
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Sounds like the bridge diodes for the exciter circuit failed. Something like this will work http://www.electronicsurplus.com/general-instruments-kbpc10-02-diodes-bridge-200v-10amp
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Diagrams and support are available from Central Georgia Generator web-site. I am not sure what 3kW heads they have handled and there are a number of variances in the basic design - so don't assume anything without double checking.
dieselgman
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Sounds like the bridge diodes for the exciter circuit failed. Something like this will work http://www.electronicsurplus.com/general-instruments-kbpc10-02-diodes-bridge-200v-10amp
THAT is an awesome answer... but why do you come to that conclusion? do these things just fail?? and why would it fail?
and, that piece on the site you linked to does not look like something from my alternator... would the same piece be this, on mine?
http://g02.a.alicdn.com/kf/HTB1_SCsHVXXXXbqXXXXq6xXFXXXN/Free-Shipping-3-phase-font-b-generator-b-font-font-b-diode-b-font-bridge-rectifier.jpg
miraculously, I have a replacement already.
thanks for the help!
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Well if it is a harmonically excited ST3 the brushes and the diodes are the only "active" components in the system. The original chinese diode bridge, at least on mine was pretty cheesey. The generic one he linked to is probably way better quality(i replaced mine with one). A bridge is also pretty generic and although it may look different will perform the same. There are two AC inputs and a pos and neg DC output, pretty straight forward.
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Yes they just fail, as mine did on an ST5 the first time the air compressor was connected. And had the same low voltage you described. Replaced with a similar one to the linked one and it's been good for 10 years now. The rectifier you've posted a photo of is for a 3 phase generator/STC. It should work if connected correctly.
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Hi Tyssniffin, yes the origional rectifiers are notoriously prone to failure. By the way the bridge in the photo looks to be fpr a center tapped transformer application. The bridge rectifiers used for ST heads only have 4 connection wires. The odds are good that a new rectifier solves your problem. Leland
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So, a couple things:
one, I replaced that old rectifier (http://g02.a.alicdn.com/kf/HTB1_SCsHVXXXXbqXXXXq6xXFXXXN/Free-Shipping-3-phase-font-b-generator-b-font-font-b-diode-b-font-bridge-rectifier.jpg (http://g02.a.alicdn.com/kf/HTB1_SCsHVXXXXbqXXXXq6xXFXXXN/Free-Shipping-3-phase-font-b-generator-b-font-font-b-diode-b-font-bridge-rectifier.jpg) )with an exact, new, duplicate, and the same thing is going on - that is, I'm not getting regular 110 out of it, but only about 8volts.
I will have to go and recheck all connections, but I probably didn't do it wrong if the same lame 8 volts is coming out.
two, wait, rectifier?? I decided to look up what I'm working on and what I see seems to say that retcrifiers cut AC down to DC... ?? why would that be there? I guess I've always ASSUMED this thing was putting out AC... and it must be, right? I mean, I've run power tools off this alternator for years now. what am I missing?
three, I see I also have an extra .. rheostat thing. (http://1.bp.blogspot.com/-D9hCk75zQ18/VbmpPExWPCI/AAAAAAAAGgI/OkA6c21g_EE/s1600/2015-07-28%2B18.30.42.jpg ) could that have failed, and created this problem?
still hoping for help
Tys
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The rectifier converts only a portion of your ac output to dc for excitation of the field windings. The voltage level in this dc circuit in effect controls the AC output voltage of the main windings.
Your rheostat control does not look like anything I have seen on standard ST heads because it is enclosed like an add-on piece. Many of the ST heads did use such a variable rheostat control so that the operator could adjust output voltage and you may be right that there is an issue with that part on yours.
dieselgman
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Ah a clue, that box says AVR which means Automatic Voltage Regulator. The standard ST3 comes with just a diode bridge is is self regulating of voltage. An AVR would typically take the 120vac output voltage and use that to power a circuit that controls the voltage. So in your case you can either get a new AVR box or switch the system back to self regulating. This assumes that someone didn't add the AVR because the Z windings are bad.
The way a generator controls output voltage is by changing the field voltage. On an ST5 the field voltage is around 48vdc. The Z windings generate some low power AC which is rectified to DC to power the field windings. See this link for more info http://www.utterpower.com/ST_manual.pdf (http://www.utterpower.com/ST_manual.pdf).
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man. this is good advice. I will swap out that AVR thing and see if that helps. So glad I asked you guys. I need to really learn this whole thing once and for all.
I will report back when I find some time to rewire in a few days,
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A picture can communicate a lot of things we might not know to when we're still learning how things work.
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Sooooooo... I swapped out that AVR thing too, and nothing changed.
BUT, just to be sure, I swapped out the carbon stick/brushes, and boom, kicking out plenty of juice. :P seems really odd that the power would cut out mid work over wear on those things. and shouldn't the springs keep those rods touching the wheel until they're too short? this looks like the wear - a 1/16th of an inch at most - was sort of uneven, on half of the stick. it's also odd that I can't move those things so they sit squarely on the wheel.
now I have a new re-wired set, and will begin to build a new box/platform for all those components, and I learned a bunch about alternators.
anyway, I'm back in business.
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Amazing, changing the brushes did it. Glad your back in operation. Were the slip rings or brushes glazed? There's almost 2.5k hours on my ST5 with the original brushes. Could you post a pic of your slip ring/brush alignment issue? I'm also curious, if you take an OHM meter and measure continuity from the wear surface of your old brushes to the lead, what reading do you get. Perhaps this is a defective brush.
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so, yeah, weird. AND worse, after kicking out 120 for a few minutes for one small job, I started it up a second time and only got 80volts now!?!?
I'm not familiar with what you're talking about with glazing -though my rings (is that the spinning surface?) do look pretty shiny. here's one side with the NEW brushes:
http://1.bp.blogspot.com/-TqBfaVJ4mYc/VcWVvb0hQhI/AAAAAAAAGgo/FSrOXBiw0hU/s1600/2015-08-07%2B17.52.51.jpg
and here's from the other side:
http://2.bp.blogspot.com/-e-6PT_tssiY/VcWVvVyWBdI/AAAAAAAAGgs/NgOIpzFU6mg/s1600/2015-08-07%2B17.53.17.jpg
I'm so confused, after years of not having any trouble from the alt, I've finally got the engine going well and now all this weirdness.
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From your pictures the brush alignment looks off a bit... and one slip ring does not appear very clean. I would clean up those ring surfaces and align the brush holders carefully. You should be able to spin the unit by hand and work it with some crocus cloth or similar fine abrasive... diamond dust (in stick form) used to be the best tool for this purpose, not sure if it is in common use or available today.
dieselgman
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I've had a bad brush situation recently on a new ST-3 from CGG with brand new brushes, properly aligned. Sanding the brush surface by slipping some 400 grit sandpaper between brush and slip ring would fix it only briefly, then it would fail open circuit (confirmed by ohm meter) again after spinning for just a minute. I think some contaminant in the brush graphite material or binder is to blame. I switched to one of the spare brushes and it solved the problem. I normally shape the brush somewhat via sandpaper on the slip ring, in order to get a broader contact area on new brushes, since the ST-3 has only 2 brushes.
This can be a frustrating problem to identify, since the brush looks fine and it will measure well when first set up (but not after it fails). Check your brush resistance from wire lead to slip ring first, is my best advice. It should be no more than 0.2 ohms more than your test leads, checked immediately after failure, before you clean or adjust anything.
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sounds like good advice.
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MORE crazy. it's working again.
ok, so, two things:
one, I swapped ONE of the brushes out for the OLD brush. who knows, I was just trying stuff.
two, given my ignorance about that rectifier thing, I should have maybe mentioned that as part of my rewiring this, I put longer wires on it, to organize the thing. so, that rectifier now has 4 18" (thicker) wires coming off it, rather than the what, 5" it had. Could I have messed up the activation voltage needed by creating a longer loop or something???
I ask, because after swapping back that old brush, I was just staring at it running at 82.3v ... and decided to play with the speed. I sped it up beyond 650, and the thing jumped up to 120v and then as the speed settled back, it stayed. ???
thoughts?
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Your wire length change did nothing. Wire length issues are for radio frequencies and perhaps some high speed data, not the extremely low frequency 60Hz power or the 120Hz harmonic excitation. You could run the wiring around the room a few times without issue.
You also seem to have gotten some bad new brushes, as I did. Once the contaminant was worn off the slip ring a bit- bingo, you were back in business. I suspect there are going to be a LOT of these out there.
Either that or you have some sort of intermittent problem...the bane of troubleshooting. Time will tell.
If you don't have one, get a cheap volt-ohm meter and learn how to measure resistance in ohms. It can help you with electrical troubleshooting greatly, and would positively confirm this bad brush issue.
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I continue to struggle with this low to no power issue. I've played around with speed, checked all connections, and I continue to feel it's the brushes, though I can no longer make a change by swapping out different brushes.
running at good speed - 650ish, but I'm not sure - I'm now getting about 50v. last week, before I started messing with it, I was getting 80something, and hardly any amps. Sometimes, I could get it up over 100v but cannot any longer.
can someone talk to me about glazing? how do I fix it? could that be it? here's photos taken today, after much fiddling. surprising to see how it looks lined up well from one side, and off-kilter from the other.
"front"
http://1.bp.blogspot.com/-5Gaq-Z2jYfI/Vhh7U3HJyxI/AAAAAAAAGmU/wqNLzKsT4tc/s1600/2015-10-09%2B17.07.53.jpg
"back"
http://4.bp.blogspot.com/-ngmUKZQ-0AA/Vhh7UsyImNI/AAAAAAAAGmQ/jrqE7OWerCo/s1600/2015-10-09%2B17.08.04.jpg
also, there is no more fixing the alignment, at least with the stock parts. They are at their maximum already.
I need to get this thing ready for winter! ???
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From your pictures the brush alignment looks off a bit... and one slip ring does not appear very clean. I would clean up those ring surfaces and align the brush holders carefully. You should be able to spin the unit by hand and work it with some crocus cloth or similar fine abrasive... diamond dust (in stick form) used to be the best tool for this purpose, not sure if it is in common use or available today.
dieselgman
is this saying I should use some abrasive on the RINGS or the BRUSH? I've run 6 different brushes in and out, both with sanding them to shape and not. still not getting there.
No, I haven't checked OHMs yet. not clear how. check the resistance, when it's not running, from the ring to the lead off the brush, or where?
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Sorry if that was not clear. The diamond dust (in stick form) would be used to re-surface the slip-ring and commutator surfaces while manually spinning the rotor. Resistance checks would be taken from brush lead to any accessible point on the slip ring in question. Replace brushes if in doubt.
dieselgman
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Looking at your pictures it looks as if the brush holder needs adjusting as the brushes are lying at an angle and not square with the rings. The brushes consequently are not making even contact with the rings, as you can see by the shiny contact area on the rings. This may have nothing to do with your voltage problem but it certainly won't help. If, as you say, no further re-alignment is possible I can only assume that someone has fitted the wrong brush holders or something has moved that should not have. I hardly think that any reputable manufacturer would put out a unit in that state.
merkland
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Looking at your pictures it looks as if the brush holder needs adjusting as the brushes are lying at an angle and not square with the rings. The brushes consequently are not making even contact with the rings, as you can see by the shiny contact area on the rings. This may have nothing to do with your voltage problem but it certainly won't help. If, as you say, no further re-alignment is possible I can only assume that someone has fitted the wrong brush holders or something has moved that should not have. I hardly think that any reputable manufacturer would put out a unit in that state.
merkland
I will continue to try and straighten that up... but I'm sure you know what I mean - there is some adjustment possible built in to the design of the piece that holds the brush holders... but I've maxed it out. if I tighten down the bolts, it ends up slightly off.
most annoying about this is that I never had a problem for the first 7 years of running this thing. (only ran it 20-30 hours a year, but still)
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maybe time to check rotor bearings and shims if fitted, for end slop
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maybe time to check rotor bearings and shims if fitted, for end slop
how and where do I do that? in the Alt? do I have to pull the whole axle?
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attempted to check Ohms. that was confusing. completely random numbers from all 6 (!) of my brushes. some of which have never been installed.
check out my test numbers, using the digital meter, with points on end of wire and end of chunk:
http://1.bp.blogspot.com/-V40LG7KS17Q/Vhnde81dzRI/AAAAAAAAGmo/_yiVscRxMe0/s1600/2015-10-10-16.png
what the what?
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Were these measured by just touching the brush with the tip of the meter probe? If so, this is why your readings are so varied. You need to put the brush in the holder and measure it from connector to the slip ring. Spin the head a bit first.
When there is contaminant in the graphite mix, the brushes may measure OK, but after spinning a bit, not.
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I was doing the measurements with it all hooked up too, with one probe on the ring, one on the end of the wire (connector end) and getting lots of different numbers. I guess I might not have been spinning it first.
is it really supposed to be as low at .2 ? I was seeing 4.1 from ring to connector. still, I'll do it again. with all 6.
thanks for the patience people.
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You might want to check the connections to the rotor from the slip rings. Just sayin.
Ron.
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Those ohm readings are way too high. About 0.2 ohms over what your test leads measure when touched together is where it should be. Bad brushes, inadequate holder, dirty slip ring? Oil is a nasty contaminate for graphite brushes/slip rings, will create this kind of issue, also.
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ok, so, crazy.
about the high numbers. perhaps my meter is just moving the decimal?
but, I did a complete test, with alligator clip to the wire end of the brush, other probe at the bottom - opposite - side of the ring. here's my crazy results:
slot A (west) slot A after spinning Slot B (east) Slot B after spinning
brush#
1 2.1 2.3 3.5 3
2 3.5 3.4 5.6 2.1
3 2 2.4 2.3 4.7
4 1.5 2.1 2 2.7
5 3.7 2.1 11.2 3.8
6 2.8 1.7 2.6 2.6
W.T.H.?
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You might want to check the connections to the rotor from the slip rings. Just sayin.
Ron.
inside the case? is that a complete disassemble?
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Looking back at your great pics of brushes and holders, it seems to me there is a helluva lotmof unsupported brush hanging out there. Perhaps someone here can tell me that's normal for an ST unit, but seems to me most other machines have the holders within 2 or 3 mm of the slipring, so that the brush is fully supported and guided. Could be there is very little spring tension and the brush is out of line and jamming when the ring rotates.
Is it possible to slot out the holes in the insulated bracket or otherwise modify to support the brushes closer to the slipring as other makers do? It could solve several problems and it seems you have little to lose. A whole new piece of insulating panel drilled to correct dimensions could be an easy fix. Sure those brushes need more support than they have at present.
Regards,
Combustor.
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What are your ohms reading with probes touching each other? (This is the test lead resistance.) What are your readings if you measure with each probe on opposite sides of the slip ring?
The ST heads do have a larger amount of unsupported brush than most other designs, this is normal, and is not likely to be your problem, as long as there is adequate pressure of brush against slip ring.
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ok, so, because I did the test with the extra alligator clip attached to the probe, I'm answering this question both ways:
west ring - with clip on one probe - .9
east ring - with clip on one probe - .9
west ring - just probes - .6
east ring - just probes - .7
probe to clipped probe (just meter to test lowest resistance): .6
probe to probe: .6
?
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The brushes may not be your problem; the intermittent problem just happened to change with changing of the brushes... or a loose wire or failing connection.
The slip rings seem fine, though the tip vs clip reading indicates a bit of glazing, so some polishing of the ring ( 400 grit on a stick held against the spinning ring- clean very well after) is a good idea. The brush connector to slip ring readings seem high to me even once you subtract the 0.6 ohms for the meter leads but I'll check my ST-3 to confirm this.
Check your rotor ohms (measured at the slip rings), also the harmonic, and stator windings ohms, now that it seems to be more reliably failed. Intermittent problems can be hell to fix.
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Also, just to make sure I've updated the situation completely:
as this thing runs, I'm getting a solid voltage out - it's just oddly low, and isn't even consistent with what I've reported earlier. Right now, it puts out 62.3 volts. if I speed it up or slow it down, it jumps around, but never jumps past say, 65v.
I certainly don't SEE any bad connections, but haven't closely examined rotors to rings yet (?)
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Once again, the rotor windings have to align with the stator windings where the harmonic windings are. The brushes have to align with the rotor slip rings to transfer the harmonic voltage to the rotor. The ST Gen Series have a history of faulty bearings full of Yak fat. You need to align the above with a dial gage and bearing shims to achieve the above first!
good luck!
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Once again, the rotor windings have to align with the stator windings where the harmonic windings are. The brushes have to align with the rotor slip rings to transfer the harmonic voltage to the rotor. The ST Gen Series have a history of faulty bearings full of Yak fat. You need to align the above with a dial gage and bearing shims to achieve the above first!
good luck!
everything seems to be in the same position as it always has been. It's been fine for years... do those things tend to move around?
could any of this have to do with a loss of 'residual magnetism'? of being turned off with a load on it?
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Please forgive if you have already mentioned this, but have you flashed the field to check excitation voltage buildup? I think your symptoms appear to preclude a problem with field magnetism to start up generation. Your field voltage may be off to cause the low output though.
dieselgman
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Please forgive if you have already mentioned this, but have you flashed the field to check excitation voltage buildup? I think your symptoms appear to preclude a problem with field magnetism to start up generation. Your field voltage may be off to cause the low output though.
dieselgman
I *have not* done that. where can I learn about how to do that? starting to google now. how's this grab, with my further questions added?
To restore the small amount of residual magnetism necessary to begin voltage buildup, connect a 12 volt battery to the exciter field while the generator is at rest, as follows:
Remove exciter field leads F+ and F- from the voltage regulator. [where/what is this on the ST3K?]
CAUTION: Failure to remove the field leads from the regulator during flashing procedures may destroy the regulator.
Measure the exciter field resistance from the F+ to the F- lead. You should be able to read some resistance as you are measuring a continuous winding. An infinite resistance reading would indicate an open in the exciter field. Also check to be sure there is no path to ground.
Connect F+ to the positive pole of the battery.
Hold the F- lead by the insulated portion of the lead wire, touch F- to the negative pole of the battery for about 5 to 10 seconds, then remove.
Reconnect F+ and F- to the regulator. Repeat the procedure if the generator fails to build voltage.
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That is a good description and instruction for field flashing. That is generally only indicated or required when you have zero output voltage due to no residual magnetism left in the rotor. In many sets, the output voltage is regulated by a small variable dc voltage fed back into the excitation windings.
dieselgman
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well, here's some more input.
while I was sitting there staring at it, I decided to wire it for 220, just to see what it would do.
it put out 110 or so, and went crazy when I put a bit of a load on it.
when I set it back to 110v (60hz), it no longer put out the 60ish it was putting out, and instead only did about 15v
is there something going on with the sine wave??
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did you have a load on it, when it spun down ? Leaving any load on the outputs will de-mag the cores, and you have to flash them again.
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I did not have a load on it this last crazy 220 experiment time, but yes, there have been times when I shut it down with a load on it, by accident.
maybe I should just flash it and see?
I'm worried though, that Dieselman said that flashing should only be for when there's NO voltage output.
(and, I'm still not clear on where best to hook up the 12v battery to this thing)
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Is your machine using an AVR control? If so, then it must be taken out of the circuit during flashing to avoid damage. If you do have that control, then it may prove to be the actual culprit in causing the wild output voltage values you are getting.
There is no issue regarding re-flashing an already magnetized unit.
dieselgman
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Is there any chance you are mixing up the harmonic winding with the stator winding? Or changing the polarity/phase of the stator windings? Are any windings shorted to ground? Something is not right somewhere and you need to start at one end and work through all the possibilities. Just curious if you hook the ohm meter to the brushes, without any Harmonic or AVR wires connected so that you are measuring the resistance of the rotor winding and brushes, and then spin the rotor, what happens? What kind of reading do you get and is it steady as the rotor turns? It's a puzzel ??? Leland
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is it possible it has a bad harmonic winding? i just went through that with a 2 pole 8kw head and replaced the factory avr with a st115 avr and bridge from CCG and a bridge rectifier and the head now works. The only problem i have is that since it takes its brush voltage from the main winding if i put a real big 220 load on the head (trying to start a 3.5 ton air conditioner)the voltage drops down pretty low and sometimes it cant recover back to normal voltage. I can load it all the way up with smaller loads one or two at a time and it works great.
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"Is there any chance you are mixing up the harmonic winding with the stator winding?"
well, I haven't been playing with any of the windings... nor did I switch the wires coming out of the case (that I assume connect up with the windings, etc) The only re-wiring I did was adding wire lengths to the AVR and the rectifier thing - and the AC output wires. AND, this thing was doing fine for the 9 years of small amounts of usage before this event.
I've put in a new AVR and a new rectifier since this started.
Thus, I don't believe I could be messing with the polarity or phase... but I'm open to ideas.
UPDATE: so I did the field flashing with a 12 volt (and made sure to not have the AVR in place when doing it). After my crazy test about setting it for 220 and then back, it was only putting out 15 v AC. Then I did the field flashing - I could hear the alt humming during the process - and then hooked it back up and started it up. It jumped up to putting out 55 volts! so, then I did another field flash, thinking maybe I'd done 2 of the 4 magnet or something, but no, another round didn't change anything.
So, now I'm up to 55 volts when doing 650rpm on the gen.
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can you measure the AC voltage going into your avr and then check the AC voltage at the rectifier. Also check the voltage at the brushes but this will be DC
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If I was troubleshooting this at this point, I'd check the field current while the engine is running and also the output voltage, as well as the field voltage. A look at those 3 things should point to the failure point. Along with repeated ohm meter readings of all the windings and checking for shorts to ground it should become obvious what is wrong. Every once in a while I've found bizarre things that I'd never suspect though :o ! One time I scraped the lighting coil on a Suzuki 250 using the wrong puller on the flywheel and then the engine had a miss when the headlight was on. Two of the outer windings were a little flattened but the coil measured perfedt electrically. Replaced the coil and spark miss was gone so I'm guessing that the shape of the magnetic field was somehow altered or weakened by the shape of the wire being changed. It didn't seem like the winding was shorted or anything, just flattened from round a little. ??? Truth is stranger than fiction... Leland
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"can you measure the AC voltage going into your avr?"
of course, there's 4 wires going in and out of the AVR (http://1.bp.blogspot.com/-D9hCk75zQ18/VbmpPExWPCI/AAAAAAAAGgI/OkA6c21g_EE/s1600/2015-07-28%2B18.30.42.jpg )
but if, when the thing is putting out 55v, I hooked up the meter to one of the white wires and the appropriate red (which goes into the alternator, not the one going to the rectifier), one was 47v and one was 24.
" and then check the AC voltage at the rectifier." - 22.3v AC
"Also check the voltage at the brushes but this will be DC" - 18.3v DC
???
"check the field current while the engine is running and also the output voltage, as well as the field voltage."
I don't have an ampmeter that will register on this thing.
the output voltage, I assume, is the AC voltage coming off the main black and red terminals on this thing. right now, it seems to just put out 55v.
what then, is field voltage? the DC off the rectifier?
???
thank you everyone for putting up with this ongoing struggle. I'm going crazy, and practically ready to just buy a different alternator. which I hate.
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just for reference, here's the little chart on the side of my AVR (everybody knows what I'm working with, right? this ST 3K chinese alt?)
http://2.bp.blogspot.com/-8TKo5Bsftqc/VjLWVAngz9I/AAAAAAAAGn8/sei0F77d9A0/s1600/AVR-chart.png
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Try feeding the AVR 48 vdc on Z windings. I think the harmonic windings or rectifier are bad.
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Try feeding the AVR 48 vdc on Z windings. I think the harmonic windings or rectifier are bad.
you mean switch the wires going in?
and, this rectifier is NEW - I switched out the old one as part of this process. I will put the old one back and try again though.
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The harmonic winding should be putting out around 48vdc after the rectifier. Your measurements show about half that. So if the avr is fed 48vdc from an external source it should have enough voltage for the field winding's to bring output voltage up to spec. If this succeeds then we have now confirmed that low output from the Z winding's or rectifier are the issue. The fix would then be either a new AVR that works of the 240 vac output or a step down transformer of a 120v leg to feed the rectifier.
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Tom, the wiring diagram he shows for his AVR is the same as CGG's- it takes one 120V leg for excitation. If it is in fact hooked up that way, the harmonic winding isn't hooked up.
Tyssniffen, It might be helpful to hook up the harmonic (aka Z winding) to the rectifier inputs, disconnecting the AVR completely. This could confirm that the AVR is at fault. To hook up the harmonic, look at the stock wiring diagram for the ST-3. Central Georgia Generator has that on their web site. Since you have an AVR, I expect it came from them.
We all assumed you had a stock ST-3, but it's apparently been set up with an add on AVR.
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There are also plenty of ST heads in the USA with AVR controls that were not imported by CGG. We purchased from several other vendors in the past with the same cheap Chinese AVR devices installed.
dieselgman
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"So if the avr is fed 48vdc from an external source it should have enough voltage.."
-- Well, I don't have another external source I could get 48v from, especially out at the gen shed.
I can bypass the AVR by following the Z1 and Z2 parts of the diagram in this manual: http://cgg1.com/index_htm_files/ST%20Manual-42013.pdf
I will also set up easy swap out connectors for my other AVR - the old one I swapped out at the start of all this.
I've gone full blow out on the wires now, and set up a working, labeled table, inside the gen shed:
http://1.bp.blogspot.com/-z_MFhWot0hE/VjPz6s-A7vI/AAAAAAAAGoM/m2xVHjmpH_U/s1600/altblowout.png
feel free to tell me I'm doing something wrong.
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Bruce, The diagram in the attached photo shows it's input coming from the z windings.
Tys, Since the voltage you measured is at 23 and the field windings require 48, this is why it's only generating 55vac output. I would guess that the output voltage will be the same without the AVR. That is unless you have two bad AVR's.
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I did the test of removing the AVR. same 55 or so volts.
Tom writes, "the voltage you measured is at 23 and the field windings require 48, this is why it's only generating 55vac output."
yes, but why aren't the field windings getting/creating 48? something not connected? something broken?
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i looked at your wiring diagram and while i am by no means an electrical expert i just went through a similar problem with a 2 pole 8kw head. It turned out that my head had a bad Z or Harmonic winding and i was getting little to no voltage out of it. Someone on here I can't remember who suggested i contact tom @ CGG as he has a AVR that will work off L1 and L2 bypassing the Z / harmonic winding. I installed this avr on my non working gen head and now it works fine. It also has a voltage adjustment.
The only issue i had (this was not the avr's fault )was that when i tried to start my 3.5ton central air the A/C would pull down the main windings voltage too far for it to recover to correct voltage and would not start the A/C. I have pulled over 7kw of resistive load on this genhead with this avr and it has worked very well it just didn't like the huge inrush current necessary to start the 3.5 ton A/C. I have since installed a quality THREE WIRE hard start kit on the A/C and now the generator will start it without any problem as the hard start has lowered the starting current required by over 50%.
Here is a link to his Ebay store but i would call him and tell him you are a member of the lister engine group and ask for a price Call CGG at 478-457-5524 (Cell) or 478-453-9358 ask for tom
http://www.ebay.com/itm/ST-115-Volt-Automatic-Voltage-Regulator-Brush-type-AVR-/151018637383
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My apologies, Tom, CarlB, Tysniffen. I confused the issue by not looking closely; I didn't notice that the AVR was also hooked to the Z windings. If the Z winding output is insufficient, it would explain why swapping AVR and bridge diodes, did nothing. Connected as shown on the AVR diagram, this AVR can only LIMIT the output of the Z winding. If the Z winding is bad, output will be too low even though the AVR ouput will be full on.
It does look like a case of bad harmonic windings, as CarlB suggested.The AVR you currently have, Tysniffen, MIGHT work if the 120V stator output was directed through the AVR where the Z windings normally go. One leg of the stator's 120V out should go straight to the bridge, the other through the AVR as your Z winding does now. Under a peak load, the Z winding will put out peak voltages higher than the 120VAC, so it should not fry your AVR.
The CGG regulator that I suggested to CarlB does work in this manner IF the problem is indeed the AVR, as it appears to be. If you will read CarlB's previous thread, you'll see that I suggested using a Variac as input to the bridge diode to confirm that the field and stator windings were all working fine. You don't need external AC power with the variac, as you can set it to the highest output voltage initially to get it started using just the stator AC input, then dial it back once the voltage comes up. Bill Rogers kindly told me of this method when I was troubleshooting my own ST-3 problems.
Again, sorry I confused things.
Bruce
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again, thank you all for the continued discussion.
I just want to be clear - I removed the AVR completely, still only gett 55v. swapped out the 'old' AVR, still got 55v.
it would seem that the above conversation is saying my Z *windings* - inside the case somewhere - are screwed up. it's not the connections? it's not how it's connected?
BruceM:
"The AVR you currently have, Tysniffen, MIGHT work if the 120V stator output was directed through the AVR where the Z windings normally go. One leg of the stator's 120V out should go straight to the bridge, the other through the AVR as your Z winding does now."
to restate for clarification: you are suggesting I wire the stator wires (the little thing that goes through that switch and light?) and hook them instead of the Z winding? can you give me more specific based on my blown out photo? which where? (I added numbers to the image for easier reference-- http://1.bp.blogspot.com/-twTt2OGOP6c/VjTwrg2y6MI/AAAAAAAAGoc/SGieKPi8hwU/s1600/altblowout.png )
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The "AC out"wires in your picture are connected to the Stator- the windings that are stationary (thus "stator") around the outside of the Rotor (the part that rotates). The one that is grounded (the "neutral") should be connected directly to the bridge, where you currently have the Z winding connected. The other of the "AC out" wires should be connected (instead of the Z winding input) to the Z winding AVR input (the terminal that does not go to the brushes). This will result in the Z windings being disconnected completely from the AVR and bridge. The "AC out" is now providing the excitation going through the bridge diode and brushes, making the Rotor into an electromagnet. The AVR will limit the current going to the bridge by chopping the "AC out" as presented to it as if it was the Z winding output.
I can't guarantee that this will work with your AVR, but it probably will.
If it isn't clear what you are doing, you should study some basic brushed generator head diagrams on the web so that you have a feel for how these beasts work. It will help you greatly should you have to do some troubleshooting in the future. Ask questions if you don't follow, please.
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" The one that is grounded (the "neutral") should be connected directly to the bridge, where you currently have the Z winding connected. The other of the "AC out" wires should be connected (instead of the Z winding input) to the Z winding AVR input (the terminal that does not go to the brushes)."
you mean run an ADDITIONAL connection from the AC outputs (coming off of U6 and U1) in the way you describe... right? I would keep the output connected to something that would put out power... and is this suggestion for a test, or as a solution? that is, would I keep it that way?
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Yes, it would be an additional connection of the AC output to the AVR, where it currently has the Z winding in and out.
Yes, it would be a permanent fix, assuming your AVR will work that way. The Z winding is not needed when an AVR is used with the AC output as the source for not just regulation sensing but also for power to drive the field coil (through bridge and brushes).
This is how CarlB solved his bad Z winding generator head problem.
I use this method on my ST-3 as well, as I don't like the waveform distortion that the Z winding makes on my particular unit.
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I have a concern that tys's AVR is probably only designed for 48vdc and that connecting 120vac to the rectifier may fry the AVR. Is there an input label on the AVR somewhere?
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there does NOT appear to be any input markings on the AVR I have. If this fries it, well, we'll know something else.
one thing I've picked up from this discussion is that AVR isn't all that great anyway.
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I have not heard of too many problems with the Chinese AVR controls... but, prefer the British Stamford in SX460 flavor. In my experience, they are very robust and reliable.
Our next shipment of ST heads will be so equipped.
dieselgman
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The ST-3 Z winding will put out peak surge load volts of over +-400 volts! I confirmed this on mine via digital scope capture, while starting only my 1/2 HP deep well pump. I expect the peak would be even higher starting a bigger motor. My homebrew AVR on 48VAC was a pathetic dog which couldn't start even a single 1/2hp motor. At 120VAC, is is not quite as good as the stock Z-harmonic setup for big motor starts, but it's adequate for my needs.
The normal ST-3 Z winding output is very NOT sine, but rather, 4 brief spikes per rotation. So the RMS (true) voltage may be only 24volts for a normal running load, but is in excess of 120V RMS for surge loads. That's why you can't beat the Z-harmonic for starting motors, and CarlB had to put a soft start kit on his compressor motor when he changed over to an AVR off of 120VAC.
So there is no concern regarding peak voltage switching an AVR to 120VAC for excitation source if the unit has worked for some time on the Z winding. There may be other design issues for an AVR, and without seeing the schematic for the specific unit in question, I can't give assurances; but it should work.
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post to wrong thread, deleted.
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sorry, looking for more clarification on this fix. (it's raining today, so I'm skipping working on wiring anyway)
I've posted another photo here:
http://4.bp.blogspot.com/-Mw48cgB_xEI/Vjfi54CUAPI/AAAAAAAAGow/G7sumGCr_tw/s1600/altblowoutwithdrawnlines.png
with GREEN DRAWN on lines of what I think is the suggested change.
Connecting on AC out (#1) to the bridge retifier and connectig the other AC out (#2) to the Z winding going into the AVR (#6) Does that all look correct?
Also, I'm unclear on whether I UNHOOK the Z windings, or leave them connected. my green slash marks are on the Z wires - do I cut those or leave them connected?
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Yes, you got it right. Both Z wires must be disconnected or cut, and insulated, as they will still have some voltage when running.
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ok, so, did that...
the voltage jumped up to 110 for a second, then went back down to low 60s... the engine acted like it had a HUGE load on it, and the alternator sounds different. and there was some 'hot electricity' smell.
I only ran it for 20 seconds or so.
I put it back the way it was, and only 3v came out. alternator sounds different.
now what?
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Well if I were a bet'in man I'd say that the field windings are shorted.
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Well if I were a bet'in man I'd say that the field windings are shorted.
how do I check, and how do I fix?
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+1 for Tom's opinion. Bad spot on your field windings... it may be cheaper to replace your ST-3 than to have the field windings replaced.
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well, can you tell me this - what might a 'bad spot' look like? I might just have some wearing out of a wire just inside the case, right? if that was touching something it shouldn't, that'd be a short, no?
and if I pull the whole axle and look at it, what might a bad spot look like? could one see it with the naked eye, or is it not testable?
Tys
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There 2 probable types of shorts it could be. One is a short between the wires in the winding. In this case the resistance of the winding will be low because instead of going through all the loops of wire, the circuit is functionally shorter. The other is a short to the metal structure of the armature. In this case the resistance between the field winding's and the armature will not be infinite. To find the exact location of either short, you'll probably need to remove the winding's unless you can see the spot that got hot and smelly. So +1 on Bruce's recommendation on a new generator.
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You can pull apart the unit and check the rotor windings visually. By separating the 4 individual coils, you could locate the bad one by ohm meter, which could then be rewound, by unwinding it, counting turns, and then rewinding it and dipping in electrical varnish. Quite a big job and not one for a novice, I think.
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so, what happened when I did the AC outs into the rectifier?
why am I only seeing 2 volts out now?
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We would hope that you fed your AC output to your AVR voltage sensing circuitry, not directly to your rectifier.
The rectifier, (and in turn the exciter windings), would be fed from the AVR outputs.
dieselgman
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What I would guess happened is that the z windings have limited amperage output. When the ac was connected to the rectifier, it's a high amperage output. Enough amps to briefly bring the voltage upto spec and then overheat at the short.
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+1 for Tom's analysis. Most likely scenario, since you had no over voltage and AVR was briefly able to regulate at 110V before the field windings failed. The field coils (4) can be disassembled and are not as difficult as the stator windings to rewind, but again, it's not a job for a novice.
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So, go the thing apart today. oy. what an ugly mess. It would appear that if what Tom said, that it got up to high amperage and then overheated at the short, the short is in the outside windings, as the only melting I can see is there, on the bottom of the circle. All the rust and rubbing are another ugly part.
Looking at this picture, does that assessment seem accurate? does that explain everything else that has been going on? how "gone" is this alternator?
(figured out how to post sort of decent sized photos here)
(http://4.bp.blogspot.com/-w2iFNxAkVL4/Vj2PmisIZYI/AAAAAAAAGp4/B2hV76RRZ5I/s1600/meltedbits.png)
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Hard to tell from the photo of your stator wingings but they look burnt in the dark area. If the windings have the electrical varnish burnt off, then that's the end of that set of windings. You'll need to have it rewound or replace it, which is likely much cheaper.
A failing stator winding would also fully account for your symptoms, including what happened when hooking the stator as the excitation source to the AVR.
Given your running environment is a bit corrosive, you might want to consider a better quality generator head for the replacement, one where the windings are sealed/dipped completely, unlike the ST heads. The best thing about the ST head is the price; they are NOT a high quality alternator. I use one for my off grid homestead primary AC power, where my typical max load is 2000 watts and my ST-3 has been reliable once I replaced failed bearings, failed diode bridge, added my own design AVR and got rid of the "doghouse". But I am in Arizona, and my engine and ST-3 are indoors in a dedicated engine shed; corrosion is not an issue. I also have a spare ST-3 on hand for parts or replacement. I am using it again on my neighbor's similar setup.
Hopefully Gary of Diesel Electric Service could suggest an alternator that might fair better in your environment. I'm just a hobbyist; his years and depth of experience/knowledge is awesome. I'm just guessing about corrosion being a factor in this failure.
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A one-time overload can cause an insulation failure between your stator windings, that failure can take time and circumstance to finally completely show up as an outright failure though. Your photo appears to show a fairly large area degraded by excess heat. If the bearings or bearing carriers allow the rotor to ever touch the stator, that will also destroy the integrity of the head very quickly. That area requires a specific air gap to be maintained at all times.
The Chinese ST heads are fine for most folks, but I would not consider them for any mission-critical applications for the reasons previously stated. It is not the Chinese manufacturing that is the primary issue here... just the fact that the STs are primarily built at absolute minimum costs. Marathon and other major brands are now made in China as well, and their reliability does not appear to be an issue. We have been using the Chinese Stamford (brushless) copies for some time now and not had any issues. Their quality is readily apparent when inspecting castings/bearings/windings and such.
dieselgman
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yes, this thing was not in the most protected environment for a number of years. of course, now, it is.
so I'm hearing, replace the stator windings (who does that?? ) OR get a completely new Alternator.
I've certainly looked at Utterpower's PMG, but I'm hoping for other specific suggestions: what should I get and who should I get it from?
--- I use my 6/1 for BACKUP for my off-grid (full time) home. That is, in the winter, from November to March, I like to bump up my battery bank because the solar panels aren't getting the long love from the sun. I also use this thing for power tool usage. That ends up being about a 5 hour stretch, once a week for 4 months, max. 80 hours a year.
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@tyssniffen:
If you can find an Utterpower PMG, get it!
No doubt you have read the specs, but if not, here is a link to general information which contains other links to specs and ordering info I think no longer available though.
I am fortunate to be using one of these, in fact, right now. A great piece of machinery, very high grade. Essentially nothing to fail, just run it at the rated RPM to give proper frequency.
Cheers,
Hugh
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yeah, looks like I'm screwed on the ideal product, as George doesn't seem to be doing them anymore. so, what are the alternatives (ha. get it?)
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@tyssniffen....Yes not in production any more. He could no longer get high grade magnets. Too bad, because these were mission critical items.
They were designed for guys like us that needed a reliable and long lived unit for off-gridding. Don't know where you are, but I get a lot less sun here in the Pacific Northwest at this time of year. I usually run about 2 hours a day to top off my batteries. Sometimes a bit more if using shop tools a lot, sometimes a bit less if we get a look at the sun.
I will PM you
Cheers.
Hugh
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The problem is finding a somewhat better 4 pole (1800 rpm) generator head at a reasonable price. I haven't seen one. I'm hardly in love with ST heads, but Marathon is way outside my budget. Stamford doesn't make a 3-5KW size.
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What about scavenging a alternator from a trashed 3600 rpm screamer ? Generally, the engines die, and the alt is likely still OK. You would have to get a mounting plate and a pulley together for it though.
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What about scavenging a alternator from a trashed 3600 rpm screamer ? Generally, the engines die, and the alt is likely still OK. You would have to get a mounting plate and a pulley together for it though.
hm. that's probably more project than I can handle, but it does have some appeal. have you seen it done, with a lister/22 inch flywheel?
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We stock a 4 1/2" and also 5" pulley for that kind of setup. It is certainly a lot less than ideal though... preferable to find a 4-pole head that you can spin at 1800rpm.
dieselgman