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In Reply to: How to set up a 274b rectifier posted by DAK on October 10, 2014 at 14:11:48:
If 5Hy is critical inductance for your current draw and voltage (the DCR of the choke factors in as well) then C1 can be very large without bothering the 274b.P.S. I'm not willing to tightly define "very large" but IMO 100uf or 200uf should not be a problem at all.
BTW, the data sheet does show 4uf as the maximum capacitance for a cap input filter in conjunction with 180 ohms impedance in each plate circuit.
If you increase the impedance you can increase the capacitance.
If you decrease the impedance you must decrease the capacitance.
For a critical choke input filter the impedance requirement is negated.
A 5Hy choke has 3.77k ohms of reactance at 120Hz.
If it's not the same, I believe there is at least a direct relationship between the math that determines the maximum cap value vs. the impedance requirement WRT a cap input filter and the math that determines the maximum cap value (of C1) vs. the reactance of the input choke WRT an choke input filter.
For all I know that too is part of the meaning of "critical inductance" and you can use as big a C1 value as you want as long as the choke meets critical inductance?
P.S.S. The critical inductance value is the value needed to keep each of the two diodes contained in the 274b conducting for their whole half cycle.
Because the diodes are each on for a much longer time (vs. a cap input filter) the current through the 274b can stay low (just a little over load current) and still replenish C1 without drawing too much current through the 274b.
Making sure there isn't too much current through the 274b is what all these requirements are in place for.
Tre'
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Edits: 10/10/14 10/10/14 10/10/14 10/10/14
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Follow Ups
- RE: How to set up a 274b rectifier - Tre' 16:06:56 10/10/14 (3)
- RE: How to set up a 274b rectifier - DAK 20:55:32 10/10/14 (2)
- RE: How to set up a 274b rectifier - Tre' 21:12:01 10/10/14 (1)
- This is great info Tre. thank you very much . nt - DAK 01:05:44 10/11/14 (0)
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