YouTube video blogger that well got it wrong!!

12 Apr 2016

You should know by know that I have a pension for things that well blow up or end badly. You can alway go to the German Safty Test video for your giggles. He now (1:52 - 2:39) draws and explains a schematic of the power supply of this silly thing. For some strange reason, he puts a transformer after a bridge rectifier. Now when I went to grade school (a long, long time ago, when we did "duck and cover") and you found out that DC will not make a magnet. You just don't create the magnetic lines of force. Also, NEVER put a cap between transformer windings. Below here is what he should have drawn:

He gets a big FAIL.

See you soon

Cris H.

Top Comments

phoenixcomm over 6 years ago in reply to mcb1

mcb1 yes in some hi-fi I have seen what is called Y caps on both Line and Neutral to Ground to help getting rid of line noise. typically they where small mica rated at 600v.
- Cancel
- Vote Up 0 Vote Down
- Sign in to reply
- More
- Cancel
mcb1 over 10 years ago in reply to michaelwylie

Are that makes sense.
Yes it is a good design practice to get rid of any harmonics that might be on the line, or are sent back towards the line.

I'm not so sure about having a cap across the primary to secondary though.
Your path would then include the filter capacitor which is typically a large electrolytic and not great at high frequencies.

The Y (or X) capacitors are often what limits the voltage that can be applied when doing Insulation Resistance testing.
We recently had some switch mode supplies that were labelled to "not exceed 385vDC", which precludes the usual electrical test voltage of 500v (for those of us using 230v mains)

Mark
- Cancel
- Vote Up +1 Vote Down
- Sign in to reply
- More
- Cancel
michaelwylie over 10 years ago in reply to mcb1

http://www.kemet.com/Lists/Filestore/EvoxRifaRFIandSMD.pdf

I remember being taught about using a capacitor across the windings of the isolation transformer in power supply designs (maybe specifically flyback?) for EMI suppression. I've never designed one, so I could be recalling incorrectly.
- Cancel
- Vote Up 0 Vote Down
- Sign in to reply
- More
- Cancel
phoenixcomm over 10 years ago in reply to mcb1

Just maybe he was thinking of a flux capacitor??
- Cancel
- Vote Up +1 Vote Down
- Sign in to reply
- More
- Cancel
mcb1 over 10 years ago in reply to michaelwylie

Aren't Y capacitors exactly for this application
not sure what you are alluding to ...
- Cancel
- Vote Up 0 Vote Down
- Sign in to reply
- More
- Cancel