ST-15 lost residual magenetism.

[Biloxibad]

I have a ST-15 been sitting for about 6 months ,  getting revs, but no electrical output to exciter Rectifier diodes, thus no output from primary windings.  It is wired for 230 v with center map for 115.  Need to give it a "boost"  to restart the magnetism.  brushes are clean and show no shorts or open circuits athrough the windings.  I know I can re-magnetise with a 12V storage batt when running.

The question is:  How do I know what polarity to attach to which winding?  I found this schematic and manual on web, but mine has a freq, amp meter and adjustable AVR in the dog house, thus my wiring is labeled differently.  What happens if i get the jump polarity wrong,  the manual says to be SURE to get it correct when restoring, and since I will be working with a LIVE running 230v  15,000 watts,  65 amps  28 HP BEAST, i would love to get it right the first time.   

Any and all help appreciated.

Here is link to ST series GEN compliments from Utterpower http://www.utterpower.com/ST_manual.pdf  which has been extremely helpful in the past.

[dieselgman]

To re-magnetize the rotor, connect a 12V storage battery to the field winding while the
generator is rotating. The positive (+) battery lead must be connected to terminal F1, the
negative (-) battery lead must be connected to terminal F2. Do not connect the battery in
the reverse direction.

I believe your real question is "How do I identify F1 and F2 ?" - clearly battery Positive to F1 and Negative to F2.

What make is your generator head? We keep a few asundry manuals around for some different ST brands and configurations. I am willing to take a look at the different identification and layout schemes to help find your specific F1 and F2 leads if that will help you.

dieselgman

[ronmar]

What does your bridge rectifyer look like?  Some of the chinese ones on the ST's are open element type, with the individual diodes visible.  The construction of the diodes or markings on them can indicate which output is supposed to be positive.  If it is a modular type(square block with 4 terminals) it should have markings around the edge to indicate which 2 terminals are the AC input, and which 2 are the + and - DC outputs. 

Another option is to mark the wires and de-install the rectifyer.  Then apply AC to the input terminals and measure the output terminals to determine which one is positive and which is negative.

Yet another option is to disconnect just the AC input connections to the bridge rectifyer and apply AC to the rectifyer input and let it work as normal to power the field and rebuild the residual magnetism...
You can make a low voltage AC source by breaking apart a transformer type wall-wart power supply and using the output from the transformer(bypass the bridge and regulator circuitry). 

[Biloxibad]

Thanks, for the quick replies,  The Unit came as a Set with the brand name Jiang Yang

[Biloxibad]

Thanks Ron, Raining now so will check when deluge is over.    Coastal Mississippi, Will probably set out onions , broccoli, cabbage and strawberries tomorrow, time to start planting here!

[Thob]

If the output of the bridge goes to the field winding, you can disconnect the input to the bridge and connect the 12v DC battery to the input of the bridge.  The output will then have the proper polarity, no matter which way you connect the input.  You don't have to feed AC into the bridge, you can feed in DC (as long as you disconnect the other input leads so the DC can't feed into the regulator, etc.).  Please be safe with this, clearly label any leads before you disconnect them and tape them up before starting the rotating.  Don't connect/disconnect things while it's rotating.

[Biloxibad]

   It WORKED! ST15 risen rom the dead. Had lost residual magnetim. Many thanks to the folks , Chris and Tom over at Central Georgia Generator for their personal help, including the phone calls and moral support..    Worked like a Charm, putting out clean stable current again, just like when new!  You guys are Great!

thanks again

[Thob]

Fantastic!  Please share what you actually did...

[ronmar]

If the output of the bridge goes to the field winding, you can disconnect the input to the bridge and connect the 12v DC battery to the input of the bridge.  The output will then have the proper polarity, no matter which way you connect the input.  You don't have to feed AC into the bridge, you can feed in DC (as long as you disconnect the other input leads so the DC can't feed into the regulator, etc.).  Please be safe with this, clearly label any leads before you disconnect them and tape them up before starting the rotating.  Don't connect/disconnect things while it's rotating.

Duhhh   Exactly right, and I only work on electronics for a living...