Re: Serious transformer problem
- From: Prune <bobysgotguns_@xxxxxxxxxxxx>
- Date: Tue, 04 Jul 2006 19:21:44 GMT
I left both connected to the mains on their lowest primary tap (least
turns, giving most output voltage), which causes the most buzzing.
After running them for an hour, the louder (lower measuring) transformer
is 15*C above room temperature, whereas the other one only 12*C above.
Two and a half hours afterwards, they seem to have settled at 48*C and
45*C respectively. I don't know if that difference is significant.
"Phil Allison" <philallison@xxxxxxxxxx> wrote in
news:4gmnk3F1np5mlU1@xxxxxxxxxxxxxx:
"Prune"
Hi Phil, thanks for the reply.
** That last one proves there is nothing basically wrong.
Off load primary current at rated voltage ( aka I mag) is a good
indicator of transformer's integrity.
If one *really* did have a lower primary inductance - Imag would be
much higher.
Thing is, even if the measurements are false readings, they're
consistent in that I get the same ratios for all windings. What
could be causing the factor-of-two difference to whatever it is the
meter is reading?
** The impedance difference you are seeing appears to be non
existent at
normal operating voltage and frequency.
So it don't matter.
I also did another test, feeding to the primaries my scope's 1 kHz
square wave. One of the transformers loads the pulses twice as hard,
as seen by their distortion on the scope. I sketched the traces:
http://img258.imageshack.us/img258/6059/square2ml.png
** Gives the same info as the DMM test.
Someone suggested to me that one of the cores may be partially
magnetized.
** Nope - the Imags would be very different.
Anyhow, an AC power transformer will de-magnetise itself very quickly
(in a few seconds) at normal voltage and frequency.
Could it be the electrostatic shield? I can't really tell for sure
if the foil may be shorting its two ends together. I tried
connecting the drain wire to a pin and poking from the side to short
it on purpose, but didn't make any difference in either transformer.
** Not at all likely - any shorted turn would stick out like dog's
BALLS in the Imag figure.
You said they were both the same - but what is the figure?
I don't want to appear I'm trying to find something is indeed wrong,
but I would like to be sure. No one would be happier than me if I
didn't have to rebuild a transformer, as I already have three others
waiting for the winding tool anyway, one a 2 kVA...
** As I said before " Such transformer primaries have very large and
NON LINEAR impedances when
tested with low and medium frequencies."
The actual value of the impedance will in part depend on just how
neatly stanked the core is - ie if all potential air gaps are closed
up very tightly, the impedance will be higher.
....... Phil
.
- References:
- Serious transformer problem
- From: Prune
- Re: Serious transformer problem
- From: Phil Allison
- Re: Serious transformer problem
- From: Prune
- Re: Serious transformer problem
- From: Phil Allison
- Serious transformer problem
- Prev by Date: Dynaco Mark VI problem : Hum, low B+ and no signal after replacing 22 ohm
- Next by Date: Re: Dynaco Mark VI problem : Hum, low B+ and no signal after replacing 22 ohm
- Previous by thread: Re: Serious transformer problem
- Next by thread: Re: Serious transformer problem
- Index(es):
Relevant Pages
|
Loading
