Opinions on adding fuses to power amp

[joseph2k]

10% conduction angle gives peak current of 20A, RMS current of 6.3A,
not too unreasonable to choose an 8A fuse in that case.

6.25% conduction angle gives 8A RMS, but that'd blow the fuse way too
often.

It takes big capacitors and toroidal transformers with really stiff
windings but many folks are building audio power supplies that way. I
personally don't like razor-thin conduction angles like 10% but that's
the style of other folks, not me!

Tim.

I don't feel like whipping up bulk supply simulation right now, please run
yours and tell me the ripple voltages at 10% conduction and 6.25 %
conduction.

 

[Michael A. Terrell]

"Nutcase Fucking ****"

Self promotion will get you nowhere in this world.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Meat Plow]

There are uses for sine, square, multiple sine, and complex waveforms in
testing. I suggest using each for what it will make esily visible in the
performance.

I've been repairing Crown, Sondcraftsman, Peavey etc...for many years.
I've used audio tones many many times. I suggested the music for this
experimental endeavor that Cook may undertake as a quick way to see what
value fuses would (hopefully) blow and what wouldn't. But nothing is
etched in stone and being knowledgeable, Cook may try multiple approaches.

 

[Meat Plow]

Self promotion will get you nowhere in this world.

Phil seems to do well for a week or two then has these psychotic outburst
episodes.

 

[Michael A. Terrell]

Phil seems to do well for a week or two then has these psychotic outburst
episodes.

Unfortunately, the psychotic outbursts outlast his lucid periods. He
really does need help. If Phil pulls this crap in the real world he'll
end up pissing off the wrong wacko someday, and will have to type his
rants with his nose.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[N Cook]

There are published guidelines for temp rise vs current, copper thickness and
track width. You'll find a chart of same in IEC60065 (electrical safety) in
fact.

The board layout guy will only use the data supplied by the design engineer.
They're not psychic. Some 'design engineers' have a clue however.



Good designers will design for that.



So what's the damn make and model FFS ! Why are you refusing to tell us one of
the most important pieces of information ?

Graham

I was having a play with track width calculator
http://www.pcbco.com.au/tracecalc.html
and assuming it is still sort of valid
at very high temps.
Putting the melting point of copper of 1080 deg C then for 3.5mm strip of
presumably 1 oz copper then the rupture current would be about 48 amps
which seems reasonable. I knew it must be higher than 12 amps as that
calculation was for round wire. By 1080 deg C we can forget about the solder
run beefings.
I think I'll leave my 60 amp transformer on the shelf - I'm happy with 48
amps

 

[N Cook]

thickness

I was having a play with track width calculator
http://www.pcbco.com.au/tracecalc.html
and assuming it is still sort of valid
at very high temps.
Putting the melting point of copper of 1080 deg C then for 3.5mm strip of
presumably 1 oz copper then the rupture current would be about 48 amps
which seems reasonable. I knew it must be higher than 12 amps as that
calculation was for round wire. By 1080 deg C we can forget about the solder
run beefings.
I think I'll leave my 60 amp transformer on the shelf - I'm happy with 48
amps

I think, assuming they survive ordinary power-ups a few times, I'll settle
on a mains side 4 amp anti-surge , with a 5 amp A/S ready to hand spare and
2 off 10 amp quick-blow in the DC lines.

 

[Tim Shoppa]

I don't feel like whipping up bulk supply simulation right now, please run
yours and tell me the ripple voltages at 10% conduction and 6.25 %
conduction.

I refuse to run such a simulation: this is the sort of stuff that was
discussed in two pages of a 1930's-era electronics textbook in the
beginning of a chapter on power supplies. Math is what a high-school
student was expected to know. You might as well ask me to run a
simulation to prove that 1 volt across 1kohm gives 1mA .

I'll give you the result: at 10% conduction angle, ripple is 5%. (If
you have a pocket calculator, the voltage at the bottom of the ripple
is Vpeak*cos(.1*pi).) At 6.25% conduction angle, the ripple is 2%.

Other handy results: 15% conduction angle, ripple is 11%. 20%
conduction angle gives ripple of 19%.

If you look a little later in the 70-year old electronics texts, they
get into I2R and other losses in transformers and making the proper
economic choice in sizing transformers and capcitors. They also get
into my favorite filtering method, choke-input! (A method at least
mentioned in the better of the more modern textbooks).

Tim.