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Biggest Transformer?

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randommscience117

Mon Jan 02 2012, 07:45AM

Registered Member #4274 Joined: Mon Dec 19 2011, 03:10AM
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Posts: 47

A transformer takes the magnetic field from the primary and steps it up to the secondary. How high of voltages could you get with a transformer the size of a car? What is the largest High voltage transformer ever made (not including tesla coils)? Things tend to not scale up very well with high voltages as far as I've heard, so what sort of extra complications would you run into at voltages above 1000Kv?
Thanks!

ScotchTapeLord

Mon Jan 02 2012, 03:04PM

Registered Member #1875 Joined: Sun Dec 21 2008, 06:36PM
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Just because a transformer is bigger does not mean it can operate at a higher voltage. The bigger the transformer, the more power it can handle. The reason conventional transformers cannot tolerate high voltage is because the iron core and layers of windings are in very close proximity to each other. Simply put, if the voltage is too high, it will arc to the core or between windings and short itself out. Tesla coils are specialized for high voltage in that there is only one layer of winding and a lot of separation between primary and secondary, and of course, no core to arc to.

Steve Conner

Mon Jan 02 2012, 04:24PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

In our high voltage lab, we have a 100kV transformer the size and shape of a trash can, made by HighVolt.

According to their site, they sell transformers up to 1.8MV, so ours is probably the entry-level model.

The higher voltage units are actually transformer cascades. Have a look at their products to get a feel for the scale of things.

Dr. Dark Current

Mon Jan 02 2012, 04:34PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

In Russia they have transmission lines up to 1175 kV, so transformers for that voltage must exist. However they won't be the size of a car, more likely of a small house.

klugesmith

Mon Jan 02 2012, 05:51PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

As STL pointed out, larger doesn't necessarily mean higher voltage, and vice-versa.

That said, very high voltage -requires- size because of insulation requirements.
And very large / heavy transformers are mostly used in connection with very high voltage power transmission.

To address the OP's question directly: S T F I !
Here is a reference to a 1 million KVA, 2000 kV transformer weighing over 700 tons.

Here are two 300-ton transformers traveling by train.

Here are a 400 ton tranformer that fell off a truck

and a pretty big one that fell off a barge (scroll way down)

[edit] By the way, transformers (like motors and diesel engines) tend to scale up very well, in terms of being more efficient. Often the upper limit is set by transportability.

Tetris

Mon Jan 02 2012, 07:35PM

Registered Member #4016 Joined: Thu Jul 21 2011, 01:52AM
Location: Gainesville, FL
Posts: 660

"shockwave" \ o3o / *emoticon throwing hands up in the air with indifferent face*

It's a transformer... from a voltage transformer. hee hee.

but really, I've seen ones pretty big. Some of them on the side of the road are big enough for me and one other person to lie down on with room.

randommscience117

Mon Jan 02 2012, 08:01PM

Registered Member #4274 Joined: Mon Dec 19 2011, 03:10AM
Location:
Posts: 47

I knew that because of insulation requirements you would have to have a bigger transformer for higher voltages to be present because of arcing to the core. So is there a point where the insulation would become so thick as to separate the windings from the core that there would be too much of an air gap and the transformer wouldn't work at all?

klugesmith

Mon Jan 02 2012, 10:32PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

You got it. But transformer efficiency does not depend strongly on physical closeness between coil and core. They just have to be topologically linked loops. For a given core area and winding area, increased spacing means the loops have to be made longer, with proportionally higher I2R and/or core losses.

As transformers scale up, the insulation becomes a relatively smaller problem.
For example, suppose your design limit is 12 kV per millimeter of dielectric (oil or solid).
The HV end of a 960 kV winding (RMS) would need an 0.08 meter gap from the core -- and I bet the core edges are smoothly curved rather than sharp corners.
Not such a big deal if the core area is measured in whole square meters, guiding a flux that induces around 1000 volts per turn at mains frequency. How 'bout 20 layers of 48 turns each? The layer to layer insulation can be a few mm of oil, for convective cooling.

[edit] I'm not trying to minimize the industrial sophistication required to make transformers that are good and big. Many, many practical details. For example, how do you make the splice when a multi-ton spool of wire runs out in the middle of a multi-ton winding?

radiotech

Sat Jan 07 2012, 08:09AM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

I have worked on and around units of 40 mVA at 66, 138 and 220 kV on the transmission
side and 13.8 on the distribution side.

It is interesting to find out how they act when faults occur, and what they do. The
other thing is, making a decision as to re-energize it after something happened is
a real problem.

You can find out a lot about these monsters by looking at the suite of instruments
hanging on them, and the controls that monitor them.

As these things get older and older, and as loads creep ever higher, its quite a chore
keeping them up

Patrick

Sat Jan 07 2012, 08:36AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

the two that fell off are funny, mostly because im not the mover, insurer or owner...

im surprised how many people in the first example dont realise how much energy had been added in the iniital fall/rotation then dissipated in the stopping provided by the dirt and gravel.

if it wheighs 300 Tons, falls 5 vertical feet and rotates 90 degrees in 3 seconds, and stops in 0.3 seconds, that might* be enough energy/inertia to bend/break steel, much less the delicate insulation or copper windings.

*and by "might" i really mean enormous force...duh.

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