Is this water in the toroidal trafo ?

[Lostgallifreyan]

"Don't bother" ?? How much stuff have you experimented with
this way to arrive at that conclusion? For the record, I've
done it many times - although I've never dried toroids.

As to running the fan if he wants to - we're talking about
a microwave oven that was thrown out. What's the problem
with modifying that?

In comparison with direct heating of the transformer core by putting
current through its windings, I don't think that a microwave oven shell can
compete. I don't need to spell out the complications of trying, for that to
be clear. For some things an indirect source of heat inside a microwave
with the fan to help get vapour out is a good idea, but it's more awkward
and far less effective in this case.

It's not so much the experimenting that matters, just the quality of
observation. I admit to not thinking of direct self-heating first, but
credit where it's due, his idea to do that IS the best one.

 

[Chris Jones]

I just did a experiment.
200 Watt 220 volt lightbulb in series with primary side.
Gives 43.3 volt on primary connectors.

OK, the resistance of the windings drops more voltage than I expected, so
using just a light bulb in series is not so wasteful. The only remaining
advantage of starting with a lower supply voltage might be safety, but if
you're careful then it should be ok either way.

And 4.6 ampere secondary, this is 50 percent overload.
Temperature went up to 60 degree Celsius and was still rising.
It is late, 01:00 at night, so i ended the experiment.


I will think about it, and see if i have suitable trafo.

What about this idea.
I have 4 trafos of 34.6 Volt 3 ampere.
All have to be dried.
What if i connect the secondary of the first trafo to the secondary of the
second trafo ?
And then the primary of the second trafo to the primary of the third
trafo. Then the secondary of the third trafo to the secondary of the
fourth trafo. And the short circuit the primary of the fourth trafo.
Oeps..
Is this crazy ? To unpredictable ?
Would be nice if it worked, could dry 4 trafos at the same time.

Or you could short circuit the secondary of each trafo and put all of the
primaries in series, with a resistance (bulb, etc.) also in series, and
connect the whole lot to the 220VAC. The heating may not be identical in
the different trafos, but otherwise I think it should work.

Chris

 

[Chris Jones]

OK, the resistance of the windings drops more voltage than I expected, so
using just a light bulb in series is not so wasteful. The only remaining
advantage of starting with a lower supply voltage might be safety, but if
you're careful then it should be ok either way.


Or you could short circuit the secondary of each trafo and put all of the
primaries in series, with a resistance (bulb, etc.) also in series, and
connect the whole lot to the 220VAC. The heating may not be identical in
the different trafos, but otherwise I think it should work.

Chris

I have just noticed that Lostgallifreyan also suggested this.

 

[ehsjr]

In comparison with direct heating of the transformer core by putting
current through its windings, I don't think that a microwave oven shell can
compete.

Ah, I see what you're thinking now. I suggested the microwave
oven/light bulb in response to this:
"The sun has not shown itself for days, and is not expected to the
coming days.

I am now looking for a suitable secondhand mini oven at ebay and such
places."

I was not proposing it to compete with the technique of passing
current through the windings - it was intended as an alternative
to getting an oven from ebay.

I don't need to spell out the complications of trying, for that to
be clear. For some things an indirect source of heat inside a microwave
with the fan to help get vapour out is a good idea, but it's more awkward
and far less effective in this case.

Regarding effectiveness, how do you know it is
far less effective? Have you dried toroids by
passing current through them? Intuitively, I
would also think current through the toroid
to raise its temperature would be more effective
at drying it than raising ambient temperature, but
I have no experience with doing the former, so I
can't estimate how much more effective it would be.
That's why I ask.

It's not so much the experimenting that matters, just the quality of
observation.

But there has to be something to observe, so it is not
clear what you have in mind.

Ed

 

[Lostgallifreyan]

But there has to be something to observe, so it is not
clear what you have in mind.

Past experience. What I do is look at anything, it might not reveal a
useful point at the time, but anything recalled later when searching for
clues or ideas helps. The various times I've tried to dry stuff in any way,
the one common flaw was in extracting vapour from a confined space. Even
with the fan, a working microwave can have vapour condensing on the walls,
and it won't insulate against heat very well, it wasn't built with that in
mind, as the contents absorb energy directly and heat doesn't get out to
the walls that easily, let alone beyond them. That set of observations led
me to think a microwave case would be good as a slow drier only, and even
then, dependent on low ambient humidity and a lot of local heat for extreme
drying.

If I needed an extreme drier in a self-contained case I'd probably buy a
cheap portable dehumidifier and put in in a small cupboard with the stuff
to be dried in front of its fan. I've got one and tried it, it's
astonishing, far better than heat alone, and with far less energy used too.

 

[Lostgallifreyan]

I have just noticed that Lostgallifreyan also suggested this.

The nice thing about the linked primaries is that each provides limiting
resistance for the other(s). Even with just two, both would have to fail to
become dangerous, although there is a need to isolate the whole rig on a
plastic shelf or something similar.

 

[Robert Latest]

I had a theoretical idea.
Put trafos in vacuum box.
Suck air out, with it the moist in the air.
Slowly add air again, while heating the air inside to 80 degree Celsius.

No. Just leave them in the vacuum. The water will diffuse out.

robert

 

[hihihi]

Ah, I see what you're thinking now. I suggested the microwave
oven/light bulb in response to this:

The microwave idea is a option.

It gave me a other idea.
The microwave is to a certain level prepared for small explosions.
This means you can use it as a safety box for experiments.
And still watch what is going on.

(I wrote the following before, but the message seems to be lost, so sorry if
this is a duplicate)

I just did a experiment with a aquarium pump as vacuum pump.
Put the aquarium pump INSIDE a plastic bag.
Lead the blowing air tube and the power cord out of the bag.
Seal the bag by winding wire around the plastic, tube and powercord.
Then i put a foam tennisball in the plastic bag.
And let the pump suck the air out.
It works
But unknown what percentage of the air is sucked out.
Here are two pictures, before and after the pumping.
http://home.wanadoo.nl/vroemm/vacuum-pump/

 

[hihihi]

I just did a experiment with a aquarium pump as vacuum pump.
Put the aquarium pump INSIDE a plastic bag.
Lead the blowing air tube and the power cord out of the bag.
Seal the bag by winding wire around the plastic, tube and powercord.
Then i put a foam tennisball in the plastic bag.
And let the pump suck the air out.

It seems to work !
I put a trafo in the bag.
After 2 hours of continuous pumping, no ON-OFF sequence.
Picture 3 and 4 show the start and after 2 hours result:
http://home.wanadoo.nl/vroemm/vacuum-pump/

It is a easy way.
Aquarimum punp is not expensive, and can be found at secondhand markets even
cheaper.
A plastic bag is also cheap.
And you do not need a real airtight seal.
In my experiment air is pumped out all the time.
This must mean somewhere air is coming in.