Author Topic: ST head prep  (Read 85244 times)

ronmar

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Re: ST head prep
« Reply #105 on: September 18, 2007, 12:57:57 AM »
You shouldn't need any fancy power supply, a couple 12V car batteries in series should do it.  I am kind of wondering why a single 12V battery didn't do it.  There isn't anything attachd to the AC output terminals is there?  A single battery running it for a little while should have made a bit of AC output and built a small residual field.  If there was nothing connected to the AC output terminals to drain away that field as the generator spun down, it should still be there when you reconnect the excitation from the bridge rectifyer.

Ron   
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Doug

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Re: ST head prep
« Reply #106 on: September 18, 2007, 01:43:41 AM »
That might be part of the problem....

Maybe a 60w bulb load and a pair of 12vdc batteries will excite things enough.

Just not sure, wish I was closer so I could see for myself and help you Zeke.

Non of the little sets I ever played with were this difficult to flash. Might be something with the steel they used. Maybe they arent even using relay steel in the rotor?
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okiezeke

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Re: ST head prep
« Reply #107 on: September 18, 2007, 02:08:44 AM »
12VDC did give me 90VAC  across the 220 output.  The local fella had a homemade rig with three light bulbs to both flash the field and give the output some load.  We tried it two or three times and it didnt work either.

I read here on the forum that the field voltage is about 60VDC.  So my choice is buying 5 batteries and some way to adjust output voltage,,, or buying this $29.00 power supply that is already fully adjustable.  As usual I have no idea how it will work, but I'll let you know.

Life is an adventure!
Zeke
Changfa type 25hp with 15kw ST head
Lovson 20-2 in blueprinting/rebuild
International TD-15 B  1962 dozer
Changfa 8 hp., 280 A battery charger

Andre Blanchard

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Re: ST head prep
« Reply #108 on: September 18, 2007, 03:26:16 PM »
Have you put a meter across the diodes in the bridge?
It really sounds like a few shorted diodes or the connections to the bridge are wrong, 2 volts is about what you would get if the AC was connected to the plus/minus pins.
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Andre' B

okiezeke

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Re: ST head prep
« Reply #109 on: September 20, 2007, 02:43:03 AM »
I've been working with 4 different bridges, all check fine.  Problem is no input voltage from the harmonic winding.
Zeke
Changfa type 25hp with 15kw ST head
Lovson 20-2 in blueprinting/rebuild
International TD-15 B  1962 dozer
Changfa 8 hp., 280 A battery charger

rcavictim

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Re: ST head prep
« Reply #110 on: September 20, 2007, 09:11:23 AM »
I've been working with 4 different bridges, all check fine.  Problem is no input voltage from the harmonic winding.
Zeke

Zeke,

I couldn`t remember what this thread was called so I posted a suggestion on another thread.  To paraphrase.  Try reversing the two field connections on the + and - bridge rectifier output terminals.  You may be trying to build a field that is reverse polarity of the natural residual  N-S field in the core.  Let us know if it works!
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okiezeke

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Re: ST head prep
« Reply #111 on: September 21, 2007, 12:28:27 AM »
Thanks, worth a try. Next time I have it running.
Zeke
Changfa type 25hp with 15kw ST head
Lovson 20-2 in blueprinting/rebuild
International TD-15 B  1962 dozer
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okiezeke

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Re: ST head prep
« Reply #112 on: September 26, 2007, 06:54:34 PM »
Very Unusual Experience!

I just had this (for me) very unusual experience.  Something that should have, in theory, worked,  Actually seems to work!  My treadmill DC motor controller arrived yesterday($29.00 from surplus center).  I wired in the 5K pot., an AC plug and 2 jumpers from the output and went to bed hopeful.

Today I hooked everything up, and started the weichai.  Then plugged in the controller.  Then nothing, but 10 seconds later all the LEDs on the motor controller lit up and I was getting 260VAC output from the ST.  A little adjusting down to 220VAC,  Then dropped the engine speed a bit to 61HZ, and I went looking for some load.

I found 3 1750 watt space heaters, and plugged them in one at a time.  Each time the engine loaded down a little, then the governor brought it right back.  At just under 5KW the voltage dropped to around 215VAC and the freq. was 60.1.  The DC output of the motor controller was around 65 VDC, and read no AC ripple.  With things running under this light load the harmonic output was 101VAC.

I was thinking about how to unplug the motor controller to see if it would excite itself....when...it ran out of diesel and quit.  Since it quit under load I probably didnt do hopes for residual magnetism any good.

The heat sink behind the output transisters on the motor board was just warm to touch.  It's rated at 8A and I connected the two output jumpers thru 2  5A breakers.  Dont have any way of measuring current draw thru the field, but doesnt seem too bad.  Next time I'll use just one 5A breaker and that will tell me a little more.

After running 30 min under load, the radiator (original) on the weichai was hot, but could still hold your hand on it. So nowhere close to boiling.

Need to find some more load and see how it acts at 10 or 12 KW, which is my expected max need.

Again, thanks to Doug and all the rest of you fine folks.  Never could have done alone.

Zeke
Changfa type 25hp with 15kw ST head
Lovson 20-2 in blueprinting/rebuild
International TD-15 B  1962 dozer
Changfa 8 hp., 280 A battery charger

Doug

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Re: ST head prep
« Reply #113 on: September 27, 2007, 05:33:03 AM »
So If I get what your sayingyou connected up this little drive and excited the field with it overnight?

Next morning you diconected it and the Harmonic winding picked up and everything is normal.....

If so Cool!!!
Although 8 hours of flashing is a little overboard 8 seconds is probably all it needs.

Doug

I'm so glad its working, you have no idea how bad I felt thinking maybe something I sugested you do had created an unforseen problem.

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okiezeke

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Re: ST head prep
« Reply #114 on: September 27, 2007, 06:24:22 AM »
I was running the ST with the motor controller exciting the field.  I'm still hoping the magnetism will come back and let me run without the external DC source, but if it doesnt, I'll just do it this way.

Doug, you've been a great help in this whole project.  Nothing you said could have de-magnetised my rotor.  It probably sat in a warehouse for 3 or 4 years and faded away.

Thanks again,
Zeke
Changfa type 25hp with 15kw ST head
Lovson 20-2 in blueprinting/rebuild
International TD-15 B  1962 dozer
Changfa 8 hp., 280 A battery charger

M61hops

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Re: ST head prep
« Reply #115 on: September 27, 2007, 08:18:31 AM »
Hey Zeke glad you got juice!  I'm not clear what the motor controller was plugged into, regular house outlet or is it powered by the ST head?  Did you check the harmonic winding for output while the generator was making voltage?  Have you tried reversing the poliarity of the output from the motor controller to the field?  If the harmonic winding generates power when exciting the field with the motor controller I would try exciting the field in each direction, then hook up a known good bridge after each test to see if you established some residual magnetism.  If there is no output from the harmonic winding I'd stick with the motor controller method.  In fact you might have a better waveform using the external exciter but I think I'd keep a spare motor controller on hand if you are going to stick with that.  If you get the ST head working after exciting the field in only one of the directions it might be that RCAvicitems theory about an embedded magnet and Dougs theory about the wrong type of steel are correct.  If you are stuck with having to use the motor controller powered by an inverter to get power when no utility power is available, congragulations on making lemonade out of a lemon!  I seem to be good at running into mysteries like this too.     Leland
I pray everyday giving thanks that I have one of the "fun" mental disorders!

okiezeke

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Re: ST head prep
« Reply #116 on: September 27, 2007, 01:34:04 PM »
Leland,
You're right, the controller is powered by 115.  I will have a battery bank/inverter on the farm, so no problem plugging it in.  I did have harmonic output with the ST running on the controller, so there is hope that some magnetism may return and I can do it the easy way.  Spare controllers are a good idea too, and at $29, easy to do.  Have to work the weekend, but will run again next week and see if I stirred up any magnetism.
Zeke
Changfa type 25hp with 15kw ST head
Lovson 20-2 in blueprinting/rebuild
International TD-15 B  1962 dozer
Changfa 8 hp., 280 A battery charger

Doug

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Re: ST head prep
« Reply #117 on: September 27, 2007, 01:34:10 PM »
Zeke:

The drive you have, does it have a pot on it called IR comp ( assuming its KB electronics ).

If so we may have the makings of an AVR....

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okiezeke

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Re: ST head prep
« Reply #118 on: September 27, 2007, 10:09:45 PM »
Doug,
It's a RU mod. MC-60.  Motor controller is for a treadmill.  There are two pots.  One came with it, had to install, controls output voltage.  The other is a little trimmer labeled r32. 
dont think I'll mess with the trimmer, since I have no tech info on the driver.  Surplus Center did say output is 0-130VDC at 8A.

I'm working on another idea on how to regulate a ST with no magnetism.  I've ordered a variac, output 0-120VAC at 25A.  With this I can feed the VR board that came with the ST with the 100VAC the harmonic would make if it werent broke.  If the VR board is working, I can rectify and filter the output to the field and I should have at least some regulation.  I just won a basic o-scope on ebay for $27.  If it works, I can look at my waveforms and work on my homemade DC filter to clean up the DC to the field.

Everyone needs a hobby.  I really enjoy this one.
Zeke
Changfa type 25hp with 15kw ST head
Lovson 20-2 in blueprinting/rebuild
International TD-15 B  1962 dozer
Changfa 8 hp., 280 A battery charger

rcavictim

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Re: ST head prep
« Reply #119 on: September 28, 2007, 11:41:55 AM »


 I've ordered a variac, output 0-120VAC at 25A.

<snip>

  I just won a basic o-scope on ebay for $27.  If it works, I can look at my waveforms and work on my homemade DC filter to clean up the DC to the field.
 
Everyone needs a hobby.  I really enjoy this one.
Zeke

Zeke,

Did you end up getting any of the scopes I linked from ebay?  There were quite a few more in the same price category that looked like good deals.

You know that variac is going to be huge.  Depending on the brand as large in diameter as your ST head and about 5 inches thick.  It could weigh about 75 lbs.  If you wanted overkill here you have achieved it since the rotating field in the ST probably only needs between one and two amps.  You could hook the output of the variac directly to the original bridge rectifier on the AC terminals that used to be fed from the harmonic winding. A large value electrolytic capacitor is added (watch polarity!) across the field terminals to improve the DC.  Someone else here did that and got a much improved output sine wave from their ST genset.  Retaining the DC motor controller may be a bit redundant but you should give it a try and see what works best for you.

Have you tried self exciiting the package yet, away from a live wall plug?
-DIY 1.5L NA VW diesel genset - 9 kW 3-phase. Co-gen, dual  fuel
- 1966, Petter PJ-1, 5 kW air cooled diesel standby lighting plant
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-6 HP Launtop air cooled diesel
-Want Lister 6/1
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