Electronics > Beginners

Is 50v cap too high for an amp with 32v power supply?

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David Hess:

--- Quote from: Zero999 on April 21, 2019, 09:44:52 pm ---
--- Quote from: David Hess on April 21, 2019, 07:18:30 pm ---Below is an example where I probably should have used even higher voltage replacements just to get a physically longer part for better mounting.
--- End quote ---

Yuck! In that case lager capacitors should have been used purely to avoid those bodge wires, which should be insulated, to reduce the risk of short circuits.
--- End quote ---

That is actually how it was originally designed!  That large capacitor was what was originally installed and it used the same wiring arrangement.

If you look closely, those wires are *not* in parallel.  Instead, that is a Kelvin connection to each capacitor lead to minimize capacitor ESR.

I should have used even higher voltage replacements to get a long enough case length to reduce the wiring length but to make up for that, I used thicker wires than the original which is shown below.

oskimac:
make sure to keep an eye on the polarity when replacing those caps... i have seen professional you tubers failing at that... :palm: :-DD :-DD   :horse:

exe:

--- Quote from: David Hess on April 24, 2019, 07:40:36 pm ---If you look closely, those wires are *not* in parallel.  Instead, that is a Kelvin connection to each capacitor lead to minimize capacitor ESR.

--- End quote ---

I understand why we need Kelvin connection on a power shunt, but I've ever seen Kelvin connection on capacitors. Could you please tell the idea behind?

David Hess:

--- Quote from: oskimac on April 24, 2019, 10:38:57 pm ---make sure to keep an eye on the polarity when replacing those caps... i have seen professional you tubers failing at that... :palm: :-DD :-DD   :horse:
--- End quote ---

I heard about some goofy Australian guy doing that once.  :-DD


--- Quote from: exe on April 25, 2019, 04:39:46 am ---
--- Quote from: David Hess on April 24, 2019, 07:40:36 pm ---If you look closely, those wires are *not* in parallel.  Instead, that is a Kelvin connection to each capacitor lead to minimize capacitor ESR.
--- End quote ---

I understand why we need Kelvin connection on a power shunt, but I've ever seen Kelvin connection on capacitors. Could you please tell the idea behind?
--- End quote ---

If the inputs are floating, which they are in this case, then running the inputs directly to the capacitor leads and then making the output connections to those points results in a lower ESR than if the capacitor leads were just extended or run in parallel.  The same idea applies to a single point ground.

Where this matters is that the high charging current on line voltage peaks flows through a minimum of resistance so adds a minimum of ripple to the output.  If for instance you added a 1 ohm resistor in series with one of the capacitor leads, then for every amp of input ripple current, the output ripple voltage would increase by 1 volt.

It can be though of as placing the capacitor as directly between the rectifier and load as possible.  It is actually a pretty common configuration but usually it is not so apparent because the capacitor is directly mounted to the printed circuit board.

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