First, mine works for about 15 years and during this time burned out 2 BY130
diodes . Second, usually the secondaries are stacked above the primary
winding. So that the upper ones have more layers of insulation between
themselves and the core (also the primary).
Third, most transformers are tested today by Hypot at 2500 VAC, so that
actually they are tested at about our operating voltages.
Actually, the reliability should be better because this design eliminates
the bleeder resistors, since they are no longer needed to stabilize the no
load voltage.
And last, not least, the dynamic impedance goes down, since, for every
capacitor the internal resistance of the winding is 8 times lower.
My transformer uses only 6 secondaries at 400V each and 6 450VDC capacitors
and it will probably outlive me!
Alex 4Z5KS
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Bill, W6WRT
Sent: Wednesday, December 09, 2009 11:05 PM
To: Amps@contesting.com
Subject: Re: [Amps] OM power power supply design
ORIGINAL MESSAGE:
On Wed, 9 Dec 2009 09:01:14 -0200, Felipe Ceglia <felipeceglia2@gmail.com>
wrote:
>What would be the drawbacks of copying such a design? Should each of
>the windings deliver the required current or should there be a safe
>margin?
REPLY:
Whenever you put transformer secondaries in series you must be careful not
to exceed the insulation rating between a secondary and the iron core, and
also between a secondary and the AC primary.
The problem is this: In the circuit shown, the transformer at the "hot" end
of the string has the full DC string of voltages between its secondary and
the core and the AC primary. Each of the transformers down the string also
has a proportionate voltage appearing there. A transformer rated for only
250 V on the secondary may not have insulation rated for several thousand
volts, because in "normal" use it would never see that much. Check with the
transformer manufacturer. Other than that, the circuit should work fine,
except that the increased number of parts also increases the odds of failure
at some time in the future.
Make sense?
73, Bill W6WRT
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|