Re: Maximum MOT`s power for long, reliable operation and life - how much is it?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Grishka <ghome@xxxxxxxxx>

>Original poster: Rob Maas <robm@xxxxxxxxx>

>I have a few Moulinex MOT's; came from 800 W microwave. The MOT's are
>labeled as class H, meaning the hottest spot can be 180 C. These
>transformers
>have been *designed* to sustain very high temp's. The power rating of these
>MOT's (according to the label) is 1440 VA (V_sec = 2300 V).

Emm, I think that 180 C is too much... Well - then, how could we determine 
MOT`s class?
Here`s a picture of MOT, that father dest has - what class is it?

http://www.ios.ru/~dest/1/12.JPG

And on my MOT I found the following:
"<KTC>
class 220
230v 50hz
6170w1d029c
23x2zpc3"
What class is my transformer?

===================================================================


>Original poster: "Peter Terren" <pterren@xxxxxxxxxxxx>

>If you look at the power consumption with input voltage you will see it 
rise very
>significantly by the time it gets to mains level (up to 4-5
>amps).
>The solution is to use a variac or an external ballast or wind an extra 
30-50 turns
>of wire in series with the primary for 240V mains and half that for 110V. 
The latter
>is only possible if you are removing the primary
>though.

>My coils use 4 MOT's under oil but I watch the current draw. My best pic 
had the 20A
>meter hard over.

Why 110 volts? IMHO it`s rather little voltage. I guess we should do the 
following -
determine the dependence of magnetising current from the primary voltage,
measure the voltage, when the current increasing becomes too fast and just 
not exceed
this voltage..
For example - if MOT is not too hot in voltage range before 200 v -  we 
should remove
only 20 volts. And 20 v 20 a - it`s only 400 w..  Let`s take a small toroid 
transformer
rated at  20 v 20 a, connect its secondary out of phase with 4 MOT pack - 
and the
problem is solved - power in such case is more, than yours one...


===================================================================


>Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>

>That is no surprise. It is instructive to look at the magnetizing
>current waveforms with the rated voltage applied to the primary and
>the secondary unloaded. You'll see straight away why it gets so hot.

Unfortunately I don`t have a variac to see how the current changes...  But 
when we
connect load to the secondary - does the magnetiing current change its form 
or its
 value? In a usual transformer it does`nt...


===================================================================


>Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

>oil is an effective cooler, especially since it can flow. However, your 
point about
>the inner windings is valid. Consider though, that there IS some air gap, 
which will
>eventually fill with oil, and the thermal conductivity of oil might be 
higher than
>that of air.

Yes, it`s right, but then you write:

>Something to bear in mind, though, is that distribution transformers (or 
any
>transformer designed for oil immersion) will be designed so that the oil 
can flow
>through it. An MOT is designed for low cost, and whether that is 
compatible with oil
>flow is unknown.

"is compatible with oil flow is unknown" - that`s it!!!  That`s why I ask 
my question -
what`s the use of packing MOT into the oil, if secondary turns are wound so 
close,
that we can`t speak about any oil circulation?!


>The wire is probably good to 80 or 100C, and that's likely to be the 
limiting factor.

And that`s too bad! Coz 80 or 100 C - it`s a big difference - it may cause 
a difference
of several hundreds of watts from each MOT in pack. What do you think about 
this "moulinex"
MOT?


>Original poster: Rob Maas <robm@xxxxxxxxx>

>I have a few Moulinex MOT's; came from 800 W microwave. The MOT's are
>labeled as class H, meaning the hottest spot can be 180 C.

And BTW Ive one more question - are the shunts able to increase the 
magnetising
current? Are they should be removed? Father dest says they decrease this 
current -
how could it be?

http://www.ios.ru/~dest/1/17.JPG
http://www.ios.ru/~dest/1/18.JPG

Now let me introduce my viewpoint: when shunts are installed, lines of 
magnetic field
are shorter, than they were without shunts. So, if these lines are shorter 
- magnetising
current would be more, coz lines flow through the shunts. And the power 
consumption
increases - am I right?


--
Best regards,
 Grishka                            mailto:ghome@xxxxxxxxx