BTO3 - SR7/2G configuration

[anomalous]

Hi folks,

I am in the process of getting an old generator up and running (it is at least 10 years old, quite likely even older). Its difficult, as there dont appear to me much in the way of markings/model numbers, but I think Ive been able to identify the alternator as a 4-pole Mecc Alte BTO3 of some kind (I'm not sure how to identify its capacity) based on technical diagrams on the mecc alte website. The regulator was a Mecc Alte SR7/1, but this blew after an hour or so of use, once we got the engine (a 3 cyl lister petter diesel) running. I have ordered an SR7/2G as a replacement.

I am in Australia, so the generator needs to provide 240V ac single phase power for it to be of any use.

currently, it appears to be configured as a parallel delta, and the previous owner had just wired a domestic power socket across one of the arms of the delta. I'm not convinced this is how to wire it correctly for single phase 240V though, and suspect this is why the regulator may have blown.

does anyone have any idea what the best configuration for 240vac single phase would be with this alternator/reg combination?

here is a link to a photo of how it is currently wired, with the blown regulator still in place:

http://www.flickr.com/photos/kyorei/5259546211/

and here are some photos of the whole unit (can someone verify my identification of the alternator as a BTO3?)

http://www.flickr.com/photos/kyorei/5260279892/
http://www.flickr.com/photos/kyorei/5259671431

thanks in advance,

Ben

[wellandpower]

Normally it is wired double delta for single phase use.
How much did you pay for the regulator, you might consider a new alternator almost for the price in some places. Always buy a genuine regulator, the copies are often not as good and can cause issues.

It looks like a BTO to me also.

[anomalous]

Normally it is wired double delta for single phase use.

so using this diagram as a reference:



my understanding is that the voltage between N,L1 and N,L2 is 120v, so 240V is available across L1,L2, correct?

all the info I can find on the BTO3 shows it having something other than an electronic regulator, so i'm not 100% certain as to how to connect the SR7/2G up in the double delta configuration. Presumably the exciter wires (blue and yellow) are connected to the appropriate inputs on the SR7. the manual that came with the SR7/2G describes a few scenarios around the supply - and the one i think the old regulator (the SR7/1) was wired in was where the supply and sensing are shared. would this connection be across L1,L2, or N,L1 in the case of the double delta? Again, the regulator manual suggests sensing should be across a single phase, so i'd guess N,L1 (or N,L2).

Also - where would the earth/ground point be connected? I think I read somewhere that the N point is grounded. Is that correct (and safe to connect to the generator chassis?)

How much did you pay for the regulator, you might consider a new alternator almost for the price in some places. Always buy a genuine regulator, the copies are often not as good and can cause issues.

I paid about $150 for it. it certainly looks genuine - the black plastic housing has "mecc alte spa" cast into it and it looks absolutely identical to all the photos ive seen of the SR7/2G. if it is a copy, its a very good one...

It looks like a BTO to me also.

I guess all that is left to determine is its rating I measured the resistance across one of the phases (or more correctly, one of the sides of the parallel delta that it is currently wired in) and it was aprx 0.8 ohms. so double that to get the resistance of one single stator coil as about 1.6 ohms, whoch from the BT03 specs, would suggest it might be closest to a BTO3-2S/4 - though now i think about it, the phase i measured was also the one wired to the regulator supply/sense, so this may fhave affected the reading. I'll check it properly when I'm up there after christmas...

thanks very much for all your help. and merry christmas!

cheers,

Ben

[wellandpower]

$150 is about on the edge of genuine I would guess, its just about possible.
I don't think you woudl ground N when using it across L1 and L2, as it will be at 110V. I would expect you to ground L1 or L2 and use the grounded one as neutral.

[anomalous]

On close inspection - comparing the alternator wiring block to the manual page that shows all the different wiring configurations, I dont think double delta is possible. this requires a 12 wire alternator, and mine is only 6 wire. The giveaway was that someone (possibly you?) posted a copy of page 60 of the ECO manual, which shows all the possible configurations for 12 and 6 wire alternators (there is a similar page in the bto3 manual I now see) - in this, the terminals of a 6 wire alternator are shown labelled U1,U2,V1,V2,W1,W2 - same as the ones on my alternator. the 12 wire terminals are shown labelled with numbers, on a larger block with 7 terminals.

so given this, I am wondering again about the best configuration. Is it possible to wire a 6 wire alternator up as a zig-zag?

the stator coils measure 0.8ohms (my digital multimeter has a resolution of 0.1ohms) which would make my alternator most likely to be a BTO3-2L (which has a listed stator resistance of 0.788 ohms) - the BTO info sheet rates this as 13kVA 3-phase, or 9.5kVA single phase delta connection. which it was how it was wired when I got it. perhaps the delta configuration is correct after all. Again, i'm a little confused here - I'd have thought a delta would have given me three 120V phases, not 240V, yet when the alternator was running before the regulator died, the voltage across one of the sides of the delta was 240V. are there different alternators for different countries corresponding to different power schemes?

each time I think I have enough information and understanding, it turns out there is a further complication but I feel I am getting close to the core of it now.

thanks very much

ben

cheers,

Ben

[merryengineer]

Yes they make different machines sometimes. Sometime 6 and sometimes 12 wire.
The 12 wires ones are a little more to make which is why sometimes you only get 6 wire machines.

I have never wired anything delta to get single phase. In the carribean, they use delta to get 220-110V 3 phase. Its just their configuration for 3 phase.

Zig-Zag with a 6 wire? I am not sure iuts possible. From the BTO3 manual:

All alternators feature both star with neutral (Y)
and delta (Δ) connections.
To reconnect from a star to delta connection
(for ex. from 400V to 230V), modify the linking
arrangements on the output terminal board
(see diagram on table 2 page 35).
It is not necessary to adjust the compound
regulator.
If required, configurations with 12 output cables
can be had, so that different voltages can
be obtained (for example, 115 / 200 / 230 /
400V).

Note however that the Zig-Zag has 6 points when reconnecting, so it might be possible.
Which page in the BTO manual were the terminals labled for 6 wire? I couldn't find that.

At the risk of blowing the alternatorup, the 12 wire version just splits each coil down again to as to allow you to have more configurations.

I think, Terminals 1,2,3,4 would combine to make 1-4, ie U1,U2, 5,6,7,8 to make 5-8, ie V1,V2 and 9,10,11,12 to make W1,W2.

Therefore on page 35 of the PDF BTO manual on the website showing the 6 wire connections for Zigzag. 1,3 are on the bottom left terminal, so this will be U1, 5 and 7, V1. 10,12,2,4 will be U2 and W2, 6,8,9,10 will be W1 and V2.
get it?
I think wired like that you will get what you desire! Do you think that is correct?