DIYbanter - View Single Post - Strange observations during a power outage

David Nebenzahl

On 3/30/2009 2:02 PM spake thus:

On Mar 29, 9:55 pm, David Nebenzahl wrote:

The other night our power went out here in Oakland. Was watching teevee
when the lights went out all of a sudden. Then they came back on. Then
they flickered a bit and went out again. Came on again, there was a
muffled "BOOM!", whereupon they went out, this time for good.

First of all, the "BOOM!" turned out to be a transformer which exploded
rather spectacularly right outside the building I'm in. Some neighbors
down the street said they actually saw the thing go, sparks and all.

I always question what makes them explode. Is it heat buildup, or
internal arcing? The cans they are in, seem like pretty hefty steel.
so it has to take quite a bit to blow them apart.

I've always wanted to see what is actually inside one of them. Is is
similar to the power transformers on electronics, such as the old
power transformers on the old tube tv sets, except bigger and wound
with much thicker wire? I've noticed the transformers inside a
welder are similar too, but that's a much lower voltage.

Yes. All power transformers for low-frequency AC are basically the same:
an iron core of some type with windings around it. Small transformers,
like the ones in audio equipment, TVs, etc., generally use "E"-shaped
cores, with one winding around each outside leg of the "E". Obviously,
the transformers the utilities use are a different configuration. I
don't know what exactly that is: does anyone know what shape they are
inside?

Another thing, what guarantees that the output voltage is correct? Do
thjey contain regulators? I'm sure the high voltage side has voltage
fluctuations, based on usage, loads, and the generation itself.

No regulators: the transformers rely on having the right turns ratio
(ratio of primary to secondary turns) to deliver the correct voltage.

--
Made From Pears: Pretty good chance that the product is at least
mostly pears.
Made With Pears: Pretty good chance that pears will be detectable in
the product.
Contains Pears: One pear seed per multiple tons of product.

(with apologies to Dorothy L. Sayers)