Re: rectifier waveform


"Helmut Sennewald" <helmutsennewald@xxxxxxxxxxx> wrote in message
news:e5d9o0$kba$00$1@xxxxxxxxxxxxxxxxxxxx
"John Fields" <jfields@xxxxxxxxxxxxxxxxxxxxx> schrieb im Newsbeitrag
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On Sun, 28 May 2006 11:16:26 -0700, John Larkin
<jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:



Following a discussion that John Fields and I have going in a.b.s.e...

Consider a conventional power transformer running off the AC line.
Assume a 12 volt RMS untapped secondary that drives a bridge
rectifier, filter cap, and a modest grounded load, producing roughly
+15 out.

What is the waveform at either end of the transformer secondary?

---
Check "Rectifer Waveforms" on abse.


--
John Fields
Professional Circuit Designer

Hello John,

I have tried to get similar waveforms in my simualation. After I increased
the
stray inductance to 500uH, it looks very similar. The remaining difference
are
bursts with about 100kHz repetiton rate when the diodes switch off in
every cycle. Maybe your scope doesn't show that because of the choosen
sampling rate.
It would require a sampling rate of 1MHz or faster. The spikes depend on
the
diodes too.

Best regards,
Helmut


I used a 'kit' transformer in the sim. With a K less than 0.995, the 500kc
ringing makes the sim very tedious.
Real life, a 100MHz scope, 100ma and IN4005's showed no nasties, pretty much
like John F's pics but smoother.
A floating measurement using two probes on the 14V~ bridge input gave 17V~
and 9V~ in quadrature. Ties in nicely with a 240V supply and measured 30pF
interwinding capacitance.
john


.

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