Author Topic: Transformer doesn't ring...  (Read 2573 times)

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Offline IvoSTopic starter

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Transformer doesn't ring...
« on: June 04, 2015, 08:03:44 pm »
I have this test jig called "Quasimodo" that is used to find proper RC+C snubber combination values for power transformer. Actually, it helps to find the RC combination "resistor" value fro two snubber capacitors which are given values of 10nF and 150nF. I tried that on few transformers and it works beautifully. All transformers will ring using this test jig.
more about the jig over here: http://www.diyaudio.com/forums/power-supplies/243100-simple-no-math-transformer-snubber-using-quasimodo-test-jig.html

Now, WITHOUT THE SNUBBER, using 300VA toroidal transformer from Plitron, rectified one side of secondaries and added a 2200M filter cap. Using my electronic load or simple large power resistor, I don't see any ringing on my scope.  When I load it with lets say 0.4A, I get nice ripples around 1vpp, but no ringing when diodes switch OFF. I probed the rectified secondary, also probed the AC straight from the transformer and all diodes one by one. No ringing observed!! According to theory, the transformer should ring more or less no matter what as the voltage goes down and diodes turn OFF. I tried regular slow diodes as well as fast schottky diodes for rectifier but got nothing. How come the transformer doesn't ring? Any ideas?
« Last Edit: June 04, 2015, 08:06:15 pm by IvoS »
 

Offline T3sl4co1l

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Re: Transformer doesn't ring...
« Reply #1 on: June 04, 2015, 08:27:44 pm »
That looks like a *lot* of hardware to go through, when one measurement and one equation is all you need...  I guess you *really* hate math.

Offhand, I would guess the toroid has less leakage than others, or a lower transmission line equivalent impedance.  Have your other tests used only shell type transformers, or does that include other toroids?

Tim
Seven Transistor Labs, LLC
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Offline IvoSTopic starter

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Re: Transformer doesn't ring...
« Reply #2 on: June 04, 2015, 09:55:53 pm »
Other smaller 15VA toroid from Plitron didn't ring either. They all ring when I put them on test jig, but they don't ring without a snubber when loaded. I tried only these Plitron toroids without snubber so far.
 


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