48V charging via ST generator and solar charge controller (no ST mod)

[mbryner]

Thanks Bob, that makes the secondaries easy.   I'm not connecting in parallel, so nothing to worry about.  I'll just put a wire nut over the black lead on the secondary, and connect in series.   If zero volts then switch leads.   Simple.    What about the primaries?

[mobile_bob]

if you have primary coils that are two pairs of green and black wires
and you are wanting to feed the transformer with 220-240vac

check for continuity and match up one green with a black to identify each 110-120 coil
then take a green from one coil and connect it to a black of the other coil

this will leave one extra green and one extra black wire hanging loose, those  two wires will now
be connected to the 220-230vac line.

to verify that you have it right before you connect to power,

while you are sorting out the two coil groups with your ohmmeter,
write down the resistance of each coil, you don't need highly accurate number here
you will find it to be X ohms

after you connect the green of one coil group to the black of the other coil group for series connection
remeasure the resistance of both groups as connected by measuring between the remaining green and remaining
black wires, you should have a reading of very close to 2X ohms.

if you have no continuity or infinity ohms, you have something wrong, go back and recheck
if you have X ohms, you have something wrong as well, go back and recheck

its late, and i think i have this right, i am sure Bruce will step up and correct me if i am wrong.


bob g

[BruceM]

Bob's wiring diagram for the primaries is wrong, he has the two 240V configured transformers in series. 

For no load wiring testing, a 2 amp fast blow would be less exciting. 
Here's my abbreviated attempt at directions:

1.Wire and confirm each transformer primaries with 240V input, checking output for 40V. If not 40V, rewire.
 
2. Connect both transformer primaries to 240V (parallel)
Wire secondaries in series.  Confirm 80V, if not, rewire.

3. Carefully mark the leads so you can rewire this easily later.

Now you're ready to find a bridge and heatsink.

The 100lb transformer might make a hell of a choke.
I'd love to measure it on my Inductance meter.

[mobile_bob]

Bruce:

please take another look at my diagram
the primaries of the two transformers are connected as series/parallel

T-1 has two primary windings and they are connect in series so that they can accept 220-240vac
T-2 is the same...

T1 and T2 as connected seperately are then connected in parallel so that they can both share
the 220-240vac line voltage

so what is wrong with the diagram?

it is not drawn incorrectly as far as i can see.

T-1 and T2 are connected in parallel as shown, not in series as you stated.

bob g

ps. i should have also stated that the use of a small rated fuse as Bruce mentions is always a good idea when
reconnecting any transformer, you never know when and if something gets mismarked or connected incorrectly
and a large flash results that scare the crap out of you... a small fuse makes a small flash and a relatively uneventful
and non damaging event should you get something wrong.

the input side of the transformer set should be fused anyway, so just use a small fuse at first to get the wiring sorted properly
is the best approach, after you get it right you can then replace the fuse with one of appropriate size.

i do this 220/440 dual primary and often dual secondary transformer thing with some regularity with control transformers
in large 3phase equipment, control transformers are generally always single phase taking power off of one leg to neutral of a three
phase system that might be 440, 460, 480 3phase or 208, 230 or 240 3phase. the transformers are made with dual primaries so that
a single transformer can be used in any of the 3phase systems at either high voltage (series connected) or low voltage (parallel connected)
with the same on the secondary side to get what is generally 24vac control voltage for the system. this allows a reduced inventory for the suppliers
basically a one size fits all sort of thing.

[BruceM]

My apologies and thanks Bob.  I'm having a rough time with vision and trying to read my computer display this week.  Your diagram is perfect.

[mbryner]

Thanks gentlemen!   I'll try it tomorrow.   What you really did is reassure me that I cant do anything too bad.   And I'm actually hooking it up to output from the batteries/inverters which has breakers.   The breakers are 20 amp though, so I'll try to put a fuse inline first.   BTW, your last diagram, bob, is excellent!

[mbryner]

I almost had withdrawals after being away from the forum for 2 days.   We went camping at our land for the night.   

So, I didn't blow anything up, and the transformers are hooked up correctly, it would seem.   Output 88 volts AC total.   First time around I got 0 volts, so the red leads were crossed.   Fixed 'em and labeled correctly.    Now, we just need a bridge rectifier and heat sink.

Thanks,  Marcus

[Geno]

That's good news. You're getting close. My flexmax display issues seem to be gone but my UPS doesn't like surge loads when it's all warmed up. I've popped the breaker 3-4 times now.

If you build your own rectifier try to find diodes with longer studs than the ones I used, or a thinner heat sink. The insulated diode mount kit is mouser part # 526-NTE439. I looked for a long time and Bruce finally got me the #. Their web site is rather daunting for the inexperienced.

Thanks, Geno

[BruceM]

Marcus, I would also suggest that since these solar charge controller's aren't expecting a "noisy" source of DC, that you go ahead and add the 0.1 uF noise suppression capacitors to your bridge diodes, also.  I can help find those parts at Digikey if you are going that way for the diode bridge parts as well.

[mbryner]

Thanks Geno, maybe I don't need a big inductive choke.   Keep us updated on the long term stability.

I can help find those parts at Digikey if you are going that way for the diode bridge parts as well.

Yes, please, Bruce.  Any suggestions are welcome.  Geno's noise filtration is easy enough, also.   Do you have any rec's regarding a simple auto transfer switch for shutting off input from the solar panels when running the Listeroid.   Or do you see a big problem with both on the same charge controller?   I would guess it would be better to isolate the two.

Thanks, Marcus

[BruceM]

Most PV setups will already have a night-time current blocking diode before the solar charge controller.

This is sufficient isolation, I don't see any problems with paralleling your rectified and filtered DC with the PV output after the diode. 

[mbryner]

OK, Digikey is a daunting website!

[BruceM]

Here's a metal film capacitor that is appropriate and cheap.
Digikey # P10730-ND

Their parametric search is sometimes a study in frustration. The catalog is about 4" thick, all fine print!

I think your bridge has to carry about 30 amps maximum...I'll look for that now.

[mbryner]

Lloyd, yes.   That why we used the toroid transformers to drop the ST head voltage down to 80 VAC before the bridge rectifier.

[Lloyd]

Lloyd, yes.   That why we used the toroid transformers to drop the ST head voltage down to 80 VAC before the bridge rectifier.

Sorry Marcus, I deleted the post, on accident. What if the PV is at full ouput at the same time as the gen, wouldn't the charge controller see over-voltage and exceed the amp?

If that is the case I know you can stack 2 controllers.

Lloyd