2 Bank question

[THE KID]

We retired a bank the other day that I have never came across and would like some insight.

Primary voltage is 13.8 delta bank was hook up delta delta all tx were 4 bussing. Center tx had center 2 bussings strap over and was 120/240.

both outside tx were strap over ac bd and were 240/480
bank was already dead and we so we didn't check voltage and it ran a building that was a machine shop. So what was the secondary voltage?



Do you build many 265/465 banks?

[Johnny Balls]

The secondary voltage would have been 240 volts measured between any two phases (delta). The two outside transformers had there coils paralleled so they were 240 volt secondary output to mach the center 240 volt transformer. I hope this helps.

[wtdoor67]

We retired a bank the other day that I have never came across and would like some insight.

Primary voltage is 13.8 delta bank was hook up delta delta all tx were 4 bussing. Center tx had center 2 bussings strap over and was 120/240.

both outside tx were strap over ac bd and were 240/480
bank was already dead and we so we didn't check voltage and it ran a building that was a machine shop. So what was the secondary voltage?



Do you build many 265/465 banks?

I don't recall ever building such or seeing such. The nominal voltage would maybe be a 277/480 that's running low or the pots have taps on them and are set for lower voltage. The relationship between 265/465 must be Wye.

Make a habit of carrying a pocket notebook and drawing these unusual hookups for later perusal. A good work diary is very useful.

On your first thing, try and note how they had the exterior bushings connected. That'll tell you what the voltage was for sure.

[THE KID]

we had a old boss that was a rigger if you know what I mean. Would have the guy build stupid shit that would work but was dangerous as hell. He was gone before I hired in thank God.

The 265/465 banks. I have built about 5 of them in 18 years but we are not building them any more. we are getting ready to retire one soon and I was explaining to my app how it works.

We would take 120/240 pots and hook them up delta on high side and wye on secondary side and run the taps up to E tap or 5 this would give you 265/465 voltage. Work good years ago and was cheaper than using 277/480 pots. Thats when motors would run on lower voltage. Motors nowday have to have voltage closer to the high end.

[Stinger]

you know the JL designation on your ticket stands for " just learning" or in some cases " Just leaving". My pont is there are days we all learn something, this is the first time I have ever heard of a 265/465 bank. Learn something everyday.

[wtdoor67]

They found one once where I worked a little at a Muni. It was a Wye/Wye with 120/240 pots. The local hands were puzzled. I think it ran some ancient motor at a grain elevator or some such. It wasn't tapped or anything. It was considered to be a 240/415 nominal voltage.

Come to think of it they did come up with one the last place I worked. Kinda funny. The job order called for a bank of 240/480 pots hooked Wye/Delta for a 480 bank. A brilliant crewmember (unnamed), said. Why we got to parallel the coils in these pots. The poor foreman was dumber than a post, so they did and connected them Wye/Wye. Voila a 240/415 bank. The serviceman, a good friend of mine, practically had an erection when he went to run the service and connect the meter. He laughed like hell and told me about it. Of course the boss just had them go and take off the lids, put the coils in series and hook it Wye/Delta. Still it was funny though.

[lineman2010]

We retired a bank the other day that I have never came across and would like some insight.

Primary voltage is 13.8 delta bank was hook up delta delta all tx were 4 bussing. Center tx had center 2 bussings strap over and was 120/240.

both outside tx were strap over ac bd and were 240/480
bank was already dead and we so we didn't check voltage and it ran a building that was a machine shop. So what was the secondary voltage?



Do you build many 265/465 banks?


What were the sizes of the power pots and the lighter pot? From what I am reading the consumer needed 240 three phase and the utility paralleled the 240/480 power pots and used a 120/240 pot to provide the light load. Just guessing, but the power pots should have been able to be half the size of the lighter pot doing it that way (two 25KVA power pots and one 50KVA lighter pot for example).


Not really sure how you get a 265/465 bank even pumping up the tap changers. With a 10% (100% at 240 volts then 10% change is all down to use only 90% of the coil) change you can get 240 volts up to 267 volts. Then if you hook that up in a delta connection you would have 267/533 or if you hook it up as a wye you get 267/461.

Granted out in the field voltages vary a little, but I am not seeing how you can get a 265/465 bank....

[THE KID]

The bank that we took down all 3 pots were 167 kva hook up in a wye on secondary side. Making it a straight 3 phase service. The motors that they had would run on 460 to 465 volts but the motors now days need to be closer to 480 volts. That why we stop building those banks.

Hope that helps. When I get a chance I will look on the tag and see what the voltage is on our pots on E tap and let you know.