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In Reply to: RE: How does the small c scenario affect the choke input? posted by DAK on March 28, 2017 at 11:08:39
There's small and there's very small. A 0.01 muF. part is used for kickback spike protection. A part less than 1 muF. is used as a "fudge factor" to adjust the rail voltage. At some point, critical current behavior will cease and cap. I/P filtration behavior will begin. What the exact value is has to be determined on a case by case basis. I'm very suspicious of both a cap. value greater than 0.47 muF. and an attempt to significantly raise the rail voltage above the RMS value being rectified. A volt or 2 above RMS might be OK.
The bottom line is that "breadboarding" and measuring, on the bench, can't be eschewed in favor of simulations.
Eli D.
Follow Ups:
Morgan Jones in the 4th ed. of his book has a pretty comprehensive discussion of this subject.
"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln
We did empirical work years ago.VOLTAGE never moved in a choke input supply until the capacitance moved past .68 uF ...Is not lost on me .68 is a benchmark value. Interestingly, the voltage never increased more after 8 uF. Perhaps with a high or lower test VOLTAGE, these numbers might change.
The Mind has No Firewall~ U.S. Army War College.
Edits: 03/29/17
Were you measuring the setups under load? I suspect you would have noticed a droop, when that 8 μF. had to supply substantial current. Small valued cap. I/P filters are notorious for poor regulation.
Eli D.
At idle Eli, there was no signal present.
The Mind has No Firewall~ U.S. Army War College.
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