Scotty, thanks for your reply! I could post a BH-curve and show you where I ran the particular design if you'd like, but I can assure you at 120Hz its WAY down in the "linear" portion of the graph. Transformer sizes in this application are 600KVA and smaller... nothing "large" by any means, but...
If I increase the output frequency on a given drive from 60Hz on the output to 120Hz, what can I expect as far as output-side transformer loss changes? The output voltage would remain the same. I am pretty sure winding losses will go up, but based on practical experience, by what factor? I...
On a 3-phase 4-wire system, is it necessary to run a disconnect on the neutral line when feeding a standard distribution bank of pole-mounted transformers? I can see how this could be a safety precaution, in the event of an adjacent phase-neutral fault while the bank in question is being...
smallgreek... that was my first suspicion... fortunately it did not pan out.
mav... after my final run of tests on friday i was convinced of this also...
So... I solved the problem. We went on site today with a bank of transformers, ready to hook them up and see if the circuit mimicked the...
The windings are 13.8KV +/- 2.5% and 2.4KV... B.I.L. for the windings are 95 and 60, respectively. 34KV/15KV are the IEEE/ANSI standards for high-pot testing at those levels.
The unit passed high pot just fine... primary winding at 34KV and 125mA, secondary winding at 15KV and 75mA.
Let me also answer some old questions that I missed.
-The megger was set on 5KV... electric megger, not hand crank.
-The high voltage induced and applied tests were done in our shop...
Well I thought about this while I was at lunch today. I must comment on our test setup, as I believe the numbers obtained in that test are more of a result of where the neutral was to begin with. At 480V and no load, my test bank shows 265, 198 and 300 volts phase to neutral. It is an open delta...
Results of single phase energizing are as follows:
All phases were energized at full voltage through the primary...
H3-H2@14490V...X0-G=259V
H2-H1@14490V...X0-G=248V
H1-H3@14490V...X0-G=139V
I am going to unground the tank from the supply and try this test again. I believe there is a ground...
prc- I am actually in the process of doing this now! I figured this would be the best way to find out which phase was contributing to the fault. I am glad you suggested the same line of testing. I will post results tomorrow. The company I work for is a vendor for the manufacturer. We do sales...
No, it just means that the inside sheet of each half is tied together so that they are on the same potential. When I say it is 8 piece, I mean its a dual 4-loop design. Picture a core cut down the middle (width) to make laminations of half the original width. The goal of this is increased...
Im not saying there isnt another ground. Ive considered the possibility myself. The problem is none of the testing showed that ground. The site has been rigorously tested... the primary cables have been energized sticking up out of the pad with nothing connected to them and no current flowed...
I will briefly outline the situation regarding my question...
-3 Phase 3 wire supply, ~13400V
-1500KVA transformer, brand new, 13800/4160Y/2400, set on 13460V tap
-energized through a recloser (setup to operate as a switch on a three minute timer)... thus all three phases closed at the same time...
