ST 5 Voltage VS Hz

[Grael]

Alright guys, small issue with my generator. If I set the Hertz to 60, my voltage drops to about 107. Now it should be around 120 of course. In the booklet that came with the head, it says to change the the air gap on the transformer to change the voltage. Only thing is that it doesn't say how... and looking at it, I see no obvious adjustment.

Anyone know how to fix this?

[mobile_bob]

you have what i have been looking for!

a transformer controlled ST genhead, cool!

the airgap is changed to alter the no load voltage, and there might also be taps
on the transformer to alter the full load voltage as well.

the airgap is between the E and I stacks laminates of the transformer core, if you look closely you will see the gap and it likely has some fiber shim in the gap. you loosen the binding bolts and iirc you narrow the gap to increase the voltage, so remove a shim or shims and gently tap the I laminations down on the  E laminations, and retighten the binding bolts that hole the core together.

then retest for voltage at no load, and work to get it up to maybe 125volts or so

after you get that set, then look for taps on the core windings and you will have to move to a different tap to get the full load voltage dialed in.

it would help if you have pictures of the head, its schematic, and especially that transformer.

bob g

[Grael]

Here's a pic of the transformer and wiring.

[mobile_bob]

that isn't an ST head is it?

in any case, look at the two bolts that secure the transformer at the bottom two
positions in the picture,  then look on each side of the transformer core just  bit above
those bolts on the outside, and you will see those two fiber shims sticking out of the
laminate stack. if you loosen the two bottom bolts you ought to be able to gently tap
on the laminate stack and free up the shim,
remove them and see if there are made up of a stack of thin shims, if so remove a bit
and reassemble,
snug up the bolts, and tap on the laminate gently to tighten up the laminate gap to grip the shims and then tighten the two bolts
retest the generator at rated speed (1800/60hz or 4pole, for 3600/60hz for 2 pole) and check you no load voltage, it should be a bit higher with a tighter airgap iirc

without a schematic i can't tell you if you have the ability to change taps for the full load voltage, however you might not have to if you get the no load voltage set right.

we really need that schematic

bob g

[Grael]

Don't think I got a schematic...

[mobile_bob]

how about a data plate?

or any numbers stamped anywhere on the case?

hard to tell what you have with just a single picture

bob g

[Grael]

I'll see what I can find. There's something on the back of the cover and I'll dig up the booklet that came with it and see what there is.

[mobile_bob]

how about a side view pic of the whole generator, and maybe
another from the rear looking forward over the top?

maybe we can tell what this baby is, that would go a long way in trying
to figure out how best to dial this puppy in.

bob g

[Grael]

Here's the wiring diagram I got out of the booklet that came with the alternator.

[cgwymp]

The top line of script is Indian, so it's definitely not a Chinese ST5....