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Posted By: Dnkldorf Pot Transformers - 04/03/06 11:38 PM
Here are a couple of pics of the Pots I am dealing with...

Looking at the nameplate, these are tappable. But exactly how do you move the HV taps on these? Appears to be a dial?

Mind my inexperience on Pots, Pls.....

(electure to post pics)

Dnk...
Posted By: electure Re: Pot Transformers - 04/04/06 12:53 AM
[Linked Image]


[Linked Image]
Posted By: circuit man Re: Pot Transformers - 04/04/06 01:53 AM
the tap changer is most likely inside the tank.it is most likely under oil. some are on the outside but very few.i have a couple of 3KVA GE pots similar to this.they are 7200 to 120/240.they have a screw for each pos.you back the screw out make your slection then put the screw back down.you would need to check the output voltages to see how close they are.this switch is there to compensate for when lower than nominal voltages are present.a word of caution some oil in the older transformers had PCB's in them.they are bad for us as well as the enviroment. let us know how it goes.
Posted By: WFO Re: Pot Transformers - 04/04/06 02:52 AM
You de-energize it first. What ever you do, don't change taps under load! [Linked Image]

Once it's de-energized, just move the dial to correspond to the percentage tap you want. You'll notice they are in 2.5% increments. If your output is 5% low on the 100% tap, go to the 95% tap. Essentially, you will be applying whatever the original incoming voltage was across 95% of the windings. The volts per winding will be higher on the primary, so the volts per winding on the secondary will be too. Do all three pots the same and double check your output before applying load.

By the way, I do business with Solomon quite often and find them to be very helpful and professional. I'm sure they would be willing to answer any questions you had about their equipment.

[This message has been edited by WFO (edited 04-03-2006).]

[This message has been edited by WFO (edited 04-03-2006).]
Posted By: Dnkldorf Re: Pot Transformers - 04/04/06 11:43 PM
De-energize it? Why?.............

I was going to ask Trumpy to contact his email buddy, and ask him if he was man enough to do this live.... [Linked Image](sarcasm) [Linked Image]


Dnk...
Posted By: gobblerhuntr Re: Pot Transformers - 04/05/06 02:45 AM
These pot may have an inspection plate on the top where the tap changer knob will be under it submersed in oil, if not you will have to take the lid off to get to the knob. Do yourself a favor and check the heat on the bushings before you go into it with a heat gun or infrared. If the bushings are showing hot or warm from the inside you may want to tighten them up while you are in there.

Oh yeah and DON'T drop any tools,washers, or other foreign matter in the pot, it makes for a long day. Not that I know anybody that has done that or anything...
Posted By: WFO Re: Pot Transformers - 04/05/06 03:18 AM
Quote:
"De-energize it? Why?............."

Didn't mean to come across like I was accusing you of being an idiot. It's just that I heard a story of an engineer once that actually did attempt to change taps through the handhole cover of an energized transformer.

I've always considered it prudent to state the obvious. Sorry.
Posted By: Dnkldorf Re: Pot Transformers - 04/05/06 11:24 AM
WFO, I didn't take that way, I knew what you meant, I just poking fun at that guy who sent Trumpy an email, in regards to him being a man because he works on live stuff.... [Linked Image]

Dnk..
Posted By: Dnkldorf Re: Pot Transformers - 04/05/06 11:28 AM
Ok guys, if the dial is under the oil, do you need to drain it out, or is the oil clear like vegetable oil, that you can see what your doing?

There is nothing wrong with the pots, I am just being curious, I don't know much about them...

Dnk...
Posted By: gobblerhuntr Re: Pot Transformers - 04/05/06 08:53 PM
You should be able to see it ok, you might want to have some rubber gloves handy though as the oil could be a little warm. I'm talking thick rubber gloves not dishwashing ones.
Posted By: ghost307 Re: Pot Transformers - 04/06/06 04:18 PM
quote
"Oh yeah and DON'T drop any tools,washers, or other foreign matter in the pot, it makes for a long day. Not that I know anybody that has done that or anything..."

I remember when I was working for GE and one of the techs tied off all of his tools and stuff before opening the cover. He tied off his flashlight so he could use it to inspect the interior. As soon as he flipped the flashlight on, the lens fell off, followed by the batteries and the rest of the guts of the flashlight.

Dang!! I wish I had been on site that day...I could have used a good laugh!!
Posted By: mxslick Re: Pot Transformers - 04/13/06 03:47 AM
Dnk:

It would probably be wisest to contact the local POCO, thier linemen/troublemen have a lot of experience in dealing with those things.

Even if the tubs are privately owned, they may be willing to take care of the tap change at no charge or maybe a modest fee.

There are a lot of factors involved, such as safely de-energizing them, ensuring no backfeed of any kind, dealing with the warm (or hot) oil, which may be PCB contaminated, not introducing any dirt, water or other foreign objects into the tank, how to actually operate the tap changer (Does it just turn, do you push it in and turn, pull it out and turn, does it take a special tool, is there a setscrew device or other locking device, etc.)

And are you prepared to deal with the possible violent failure of one or more of these if the tap changer or windings are bad? The POCO guys I know have told me horror stories from doing what they thought was to be a simple tap change.

If I were in your shoes, I wouldn't touch 'em. I don't have the necessary experience. I've read a lot about them, but I don't consider myself anywhere near qualified to deal with them!! [Linked Image]

Good luck!!
Posted By: subtech Re: Pot Transformers - 05/17/06 12:42 AM
Dnkldorf
Although it isn't impossible that the tapchanger control knob is inside the tank, it's very highly unlikely. It should be somewhere on the outside. It is usually a composite (plastic) knob or lever and should be held in its present position by a set screw or similar. Completely DE-ENERGIZE the transformers before doing anything! ( I know you already know that, but others who happen along to your post may not read everything. I would hate for someone to end up dead, or worse) Previous posts gave the correct instructions. If your present input voltage is 5% lower than the nameplate rated volts, move the tapchanger to the 95% position. Oh, by the way, make really sure you re-tighten the set screw, you would be some surprised what a medium sized curious raccoon can do with that tap handle! Always re-energize from a safe distance whenever possible.
Regards
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