ST head prep

[Doug]

I like using TEW wire for general control wiring. Its has more strands and is easier to bend and shape neatly than cheaper TW wire ( also its a little better in the heat ).

Generaly we used a silicon rubber insulated wire with a temp rating of 130C, but you caould just as easily get some general purpose hi temp apliance wire ( stuff has a braided Nomex jacket ) and itys up to the task ( and an ST head doesn't get very hot )

For those reading this I would also recomend you use a minimum 90c rated wire when wiring to generator heads and in some cases you are forced by the code to use a hi temp wire in the generator junction box if it has class F or higher and is tottaly enclosed  non ventilated.
Not an issue with the ST since it realy open and the box they come with is a joke.

TW wire is rated at 75 C ( or is it 65 c ) not sure. I never use the cheaper stuff and it sgetting kind of rare to find electricians who do for homes ( NMD 90 is the standard ) but be aware if you order wire or EBay a spool it might be the cheap TW crap and you might be disapointed.

[okiezeke]

Doug,
I did the repair.  After cleaning and crimping new lead wire to the ends of the aluminum field wires I safety wired  the connectors to the insulator sheet on the rotor and epoxied the connection down tight with JB weld.  I dont think the aluminum wire ends will vibrate at all, and hope for a permanent fix.

Next problem....  I have the new AVR in hand and want to try it out.  The high tech hicks say to maintain field polarity.  Since I ripped out the feed wires to the field, I dont know which is pos or neg any more.  Is there any way to measure  field polarity, and does it really matter?  This is the gen that had no residual magnetism until I remagnetised it by exciting the field externally.

Thanks,
Zeke

[rcavictim]

Doug,
I did the repair.  After cleaning and crimping new lead wire to the ends of the aluminum field wires I safety wired  the connectors to the insulator sheet on the rotor and epoxied the connection down tight with JB weld.  I dont think the aluminum wire ends will vibrate at all, and hope for a permanent fix.

Next problem....  I have the new AVR in hand and want to try it out.  The high tech hicks say to maintain field polarity.  Since I ripped out the feed wires to the field, I dont know which is pos or neg any more.  Is there any way to measure  field polarity, and does it really matter?  This is the gen that had no residual magnetism until I remagnetised it by exciting the field externally.

Thanks,
Zeke

Zeke,

Being an AC machine the polarity of the residual magnetizm only matters in how the bridge rectifier is oriented.  Wire it up and try it.  If the field does not build up right away shut down and reverse the DC taps running to the slip rings on the bridge recifier.

[okiezeke]

Sparkey,
Thanks again, I'll let you know how the AVR functions.
Zeke

[Doug]

Rob's right hook it up and try....

By wire you mean nylon string right?

Real wire is not a good choice since its conductive and steel wire because its permiable...

[okiezeke]

Doug,
Oops, I used some stainless safety wire around the connector to the winding insulator.  It's non magnetic, and not close to any other hot wires.  Will take it out if you think it will cause problems.

Tried the new VR today.  One thing is very consistent in my recent efforts.  Nothing works when I first hook it up.  The residual magnetism seems to have died again.  I had no output with the gen at 1800rpm.  Tried flashing the field 2 or 3 different ways and still no output.

Stopped the engine and traced every wire and checked every connection in the field ckt, and all looked OK.  Double checked the new AVR instructions.  Still no output.

Shut it down again, completely removed the new AVR from the system.  Hooked up my variac-bridge-capacitor jury rig.  Restarted and dialed up the input voltage.  Blew the bridge and the variac fuse.  Cussed a little(I'm a firm believer that profanity really does help).

New bridge(I buy them by the gross) new fuse.  Started the engine and turned up the input voltage very slowly.  Aha!! smoke rising.  Being of american indian heritage I could read the signal that was being sent.  "You have a direct short across the 240VAC output you dumb s@#t!"

And there was.  Somewhere in the cable from the 100A breaker to the electric range.  Had never seen a breaker smoke before.  Thought they would just pop open.  Not always.  Removed the shorted output cable and re-installed the new AVR.

Started the engine and still no output.  Flashed the field with 60VDC and the output voltage appeared.  Tweaked the adjustments on the avr and had 240VAC at 61 HZ in no time.  And it only took me most of 3 hrs!

Since I couldnt use the range for a load, I plugged in a 1.5KW heater to each 120V leg.  Slight change in engine tone, voltage dropped from 120 to 118.5, freq dropped a tenth.  AC voltage reading across the field input is 1.8V, so mabe not too much ripple.

Plan:  Repair the cable for using the range as a load.  Get the O'scope on the AVR output and see what the 1.8V looks like.  Put the system under 9KW load and see what it will do.  See if there's any of that 12 year old whiskey in the cabinet. 
Zeke

[Doug]

If you can get some nylon Nomex would be better string and remove the Steel safety wire.

I just don't trust that spinning around, but if you are absolutely sure it can't come free and non of it is running parralel ( ya I butchered another word Ray where are now ? ) to the shaft so no currents are induced in a closed loop.

JB weld should be fine provided there is no metal in it and it doens't get hot.

Mail me the lable off that bottle.
Might not be able to join you for a drink and some testing but I can read about and lick the sticker....

[mike90045]

Oops, I used some stainless safety wire around the connector to the winding insulator.  It's non magnetic, and not close to any other hot wires.  Will take it out if you think it will cause problems.

Copper is non-magnetic, but it still gets a voltage induced in it.  Same with aluminum wire.
    conductive + motion + magnetic field= voltage

Voltage in a short = heat

[Doug]

if its around the shaft and not paralel to it, it won;t cut any flux and won;t have any significant current induced. Stainless steel is not a particularly good conductor and that works in his favour...

It is already epoxied in its probhably more trouble and risk to remove it now.

[okiezeke]

I'll keep an eye on it and check for any signs of heat.
Zeke

[shipo]

Doug,

I will replace the cable on both of my ST, 3 and 10, and I do not know which cable to order from McMaster. 

 What would be your recommendation to use cable, THHN and MTW. I would like to buy only one size to be use it in both, if possible, please specify the AWG and amps.

Thanks in advance 

OC

[GIZMOS]

Thanks Doug, that’s very good information.
Question: My slip rings are pretty round but not quite straight on the shaft so I get a side-to-side wobble. It’s not enough to cause the brushes to lose contact so I thought I would be OK. One set of brushes and its ring is wearing faster than I thought it would. I stepped up my cleaning of the area and I’ll see what happens. Any Suggestions? Also, if I’m not mistaken once the ring is worn out I’m pretty much screwed. They don’t look replaceable.

Thanks, Geno

I actually managed to import some spare slip rings so they are replaceable -  next time I do some inspections Ill pull down theh ead and see how hard they are to changeover - Matt Richards former owner of OzListeroids will know

Stephen Hutson
Ozlisteroids Australia
Offgridder CS10/1 ST5
Lister FR2 16 HP
Cummins 4B 3.9 22.5KVA

[Doug]

Most rewind shops can also replace slip rings ( if they are any good at their job anymore that is )

Once the rings are one they should be cut and trued on shaft and the new brushes should be stoned to seat and the whole assembly checked to see the brushes are riding the ring correctly and smootly.