One for you transformer GURUs

[dbrown20]

This is just for thinking. Probably would never be done. You are working trouble alone in a rural area and locate a bad pot. The primary is 7200 single phase with only neutral and phase present. The secondary is 120/240 and the customer is in dire straits. Breathing on an oxygen apparatus and his back up generator won't start. I know in normal circumstance you would just call an ambulance but this is just to make you think.

You determine to change the pot alone to expedite things. You're on good terms with the local REC and have a key to their yard which is about a quarter mile away. Your own yard is about 25 miles away. The REC runs all 14.4/24.9 and that is the only kind of pots they keep in their yard. They have pots of all sizes and secondary voltages but all only 14.4/24/9. You have a brain storm. What do you do? Hemingray, what's your take? dbrown20

[44kv]

could you take 2 pots from the yard and use one as a step up two 14.4/24.9 and use the other one as your pot to bring it back down to 120/240. Just a question i dont know just wondering if it would work?

[BigClive]

My guess is that you might under extreme circumstances wire two 14kV pots primaries in parallel and their secondaries in series to get the required voltage. Not sure if this is an ideal situation though.

[dbrown20]

My guess is that you might under extreme circumstances wire two 14kV pots primaries in parallel and their secondaries in series to get the required voltage. Not sure if this is an ideal situation though.


Clive to have never been an Electrical lineman, you're pretty damn sharp. Don't know if that would be a compliment though. Your method would work but it's not the exact answer I'm looking for. dbrown20

[Hemingray Insulators]

#1But you could hang a single 14.4 pot and get 120 across the entire secondary and find out what leg his oxegen machine is on, as oxegen machines only run on 120. make sure to remove the ground strap on x2, and make x1 neutral and x3 hot leg.

#2 You could grab 2 pots and head to the closest working xfmr and cut an inline deadend and back feed 1 pot go the ther bad pot an hang the other there.

I'd probably do #1, the guy can do with a 120 service till you get a different pot.

[dbrown20]

It would work Hemi. You're too sharp to be a lineman. However it's in the summer and the poor guy also wants his air conditioner to run on 240. Close, but not the exact answer yet. dbrown20

[BigClive]

Clive to have never been an Electrical lineman, you're pretty damn sharp. Don't know if that would be a compliment though. Your method would work but it's not the exact answer I'm looking for. dbrown20

A transformer is a transformer whether it's the type you can pick up in one hand or the type that needs pulled up with a block and tackle. As long as you know the winding layout and whether there are internal earth links on any of the taps, then you can configure the windings as desired. Your question scales nicely to "narrowback" transformers. :)

(But ours don't blow your limbs off if a wire pops off. :eek: )

From what I can see electrical theory itself is a pretty small part of linework compared to the mechanical theory and actual experience required in the multitude of installation techniques.

Just out of interest, how many secondaries do the REA's 14kV trannies have? I'm wondering if seperate groups could be seriesed on a single transformer to turn two 120/240 windings into a single 120/240 winding utilising the lower primary voltage.

[wayne440]

Is there a 480 v transformer in the yard with a secondary center tap? It would be right at 120/240 on a 7200v line.

[hifihaxor]

i would have originally suggested clives idea, but he beat me to it. transformers are nice because you can series and parallel windings, and everything works on ratios, which is why the math part of my brain likes them so much

waynes idea works too, we use 7620/13.2 dual voltage with a 240/480 sec for streetlights (which is where my experience is), so i could see that working if it was available

as a FURTHER option, using 2 txes, get one set up like hemi mentioned, running the primary at half voltage to get 120 out of the hot legs of the series connected secondary windings, then hang a second pot (of equal size, i think?), leave the primary unconnected and use the secondary side as an auto transformer by hooking the 120 you not have between one leg anmd a neutral and then you get a synthesized second leg 180 degrees out of phase witht he first, giving you 120/240.

we have things called phantom phases that they set when one leg or a neutral goes bad on a secondary urd service, its an auto transformer and will make either a hot leg or a neutral given the other 2 wires are good.

i think it would work?

[BigClive]

Another option might be to wheel the guys bed along the line until you found a working pot and drop a bit of romex down with crocodile clips on the end for a temporary connection.. :rolleyes:

In hindsight if there were 240/480 transformers available with a 14kV primary then one of them would do the job as mentioned by hifihaxor.

[dbrown20]

Is there a 480 v transformer in the yard with a secondary center tap? It would be right at 120/240 on a 7200v line.

That's it. Wayne, you da man. I think Clive figured it out too. You guys are smarter than a bunch of electric foxes. dbrown20

[toptie]

to bring a simple fix to your situation, why not call your dispatch, or even maybe the local fire dept., or just 911? Then aline crew could put everything back to normal? :rolleyes:

[toptie]

ssorry about that , but I was speaking in terms of generators. :o

[scammy]

what I would do is plug him up to my inverter, if I didnt have one ,then the above mentioned would be the rought to go ,,,,,these folks count on us ,,,be safe and carfull ,,,,,scammy (some times we dont have time as a luxury)

[dirtdobber]

how close is his house to his neighbor? you could always run a temporary ground strap from closest neighbor.

[dbrown20]

It's just a thinker dammit. Don't get carried away. dbrown20

[edski104]

hummmm, how about dig a ditch, put a little armature at the end for a generator, hook up the wiring,go divert a river and there you go,instant electricity. but carried away, us??? never,my friend, never.

[BigClive]

Or put some floats on his bed and a wee turbine driven generator underneath and chain it all to a bridge.

[dbrown20]

You blasted,bloody blokes are bloomingly brilliant. And some of you other chaps, not so shabby either. dbrown20

[Apples]

Shoot the gasper. Call a crew. Go for coffee

[dbrown20]

You blasted,bloody blokes are bloomingly brilliant. And some of you other chaps, not so shabby either. dbrown20

Just kidding Clive. I know you Scotties don't talk that way. Do you? Have to be careful and not rile up the wee Scotsman. dbrown20

[tramp67]

I vote for Apple's solution to the problem! But, if you are trying to push a rate increase through, I suppose the 14.4/480 pot would be my second choice. :cool:

[BigClive]

Just kidding Clive. I know you Scotties don't talk that way. Do you? Have to be careful and not rile up the wee Scotsman. dbrown20

We do actually swear a lot. The word "fuckin'" (note the guttoral stop at the end) is used as punctuation in most sentences uttered by blue collar trash like myself. (Well paid highly technical blue collar trash to be precise.)

Scotties are dogs. Nasty little yappy ones at that.

Wee Scotsman? 6'4" very broad shouldered and about 250 pounds of mean mutha here. Not so wee after all. Wanna fight anyone? :)

[CenterPointEX]

Can you say Terry Shivo?

[BigClive]

Can you say Terry Shivo?

Who? :confused: