Original poster: Don Murray <don@xxxxxxxxxxxxxxx> Hi Gerry R.The bottom line is that that transformer can only take 7200 volts. Over volting it can cause arcing in the can and that can cause acetyline gas to form in the can, very bad, tends to blow the lid off next time there is an arc in the can.
On large substation transformers we sample the oil for desolved gasses,acetyline indicates some arcing, methane can show that the paper insulation is breaking down, there is one more that shows that the transfomer has over heated but I cant think what gas it is right now. This has to be ongoing as you need a base line to watch for changes. And some of the real big transformers(230kv to 115kv) have a nitrogen bottle that keeps 3 to 5 lb. of blanket pressure on the oil.
Another type of transformer found in older 4kv (4160V) areas, that yourarely hear about, is an RO (regulated output) transformer, these put out constant current. They have two types, 3.3amp and 6.6amp. The way they did this is with a movable core on a counter balance. They were used for series street lighting. The voltage would vary with the number of lights. If the series street light circuit opened up (light burnt out) the RO would go to maximum voltage, around 5kv. In the base of the light socket there are two contacts with a wafer in between them that would burn through and the circuit would come back on. Have any of you ever got to play with a RO transformer?
Don Tesla list wrote:
Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx> Hi Don,So what is the bottom line on a PIG with a HV spec of 7200/12470Y. With regard ONLY to what the PIG can take, can you put 12470 across the two HV bushings??? (no consideration to what kind of service you want only what the PIG can take).Gerry R.Original poster: Don Murray <don@xxxxxxxxxxxxxxx> Justin, What the Y means is that if you are going to connect that transformer to a 12470 volt system you must connect it Y. Each end of that Y is one phase of a 12470 volt system and each leg of the Y would be one 7200 volt coil. On a delta system each corner of the triangle is one phase of a 7200 volt system and each side would be a 7200 volt coil. Draw it out and you will see. What determines if we Y or delta the high side is coil rating and primary voltage, if they are the same it will be delta, if primary is higher it will be Y or star as they are the same. And what determines if you get a delta or Y low side is the service voltage you want. If you want 120/240 it will be delta, if you want 120/208 it will be Y. On the high side of a Y connected bank of transformers you don't always ground it. Some times you let it float. And you don't always have to have 3 transformers, you can have open delta and open Y with 2 transformers. I have some transformer connections on my web page that I put up for a discussion on a usenet group, thought they might help some. The Scott connection at the bottom of the page is for 3 phase to 2 phase. They take special transformers and are pretty rare. http://murrayranch.com/Electricity.htm Don Tesla list wrote: >Original poster: Justin <rocketfuel@xxxxxxxxxxxxx> > >Hi All, >Just an update, here are the specs on the pig: >15KVA >Rated Volts: 7200/12470Y 120/240 >2.2% impedence >Orto Filled >http://jay.g-cipher.net/pig2.jpg >http://jay.g-cipher.net/pig1.jpg > >I'm curious what the Y means in the "12470Y"...any ideas? > >Thanks as always! >Justin Snip>