One last question: Does the resistor in the secondary provide any benefits
over a proper value resistor located in the primary circuit?
73,
Gerald K5GW
In a message dated 2/11/2010 8:55:31 A.M. Central Standard Time,
Jim.thom@telus.net writes:
OK, Now that I have the latest version of psud... it just reafirms my
real life test, done on a 3100 vdc real supply,
using a 46 lb dahl xfmr.... and a 25 uf cap....... and a 22 ohm
resistor BEFORE the 25 uf cap.
I used the 2000 vac tap on the 46 lb dahl [ it has taps for
1500/2000/2500/2750]
Pri is DUAL 110 vac windings.. with windings in series. [220 vac] .. and
240 vac stuffed into it. [ sec ends up a little , at 2181 vac]
220 vac pri = .16 ohm dc resistance
2181 vac sec = 25.5 ohms dc resistance
Input Z of xfmr is = 38.72 ohms
25 uf filter.... [ 8 ohms esr, old style 200 uf caps were 1 ohm esr
each... 8 x caps in series]
Load is 900 ma cxr.
Results WITH 22 ohm resistor inserted B4 the 25 uf cap.
vdc across load = 2752 vdc [UNDER A 900 Ma LOAD]
V drop across 22 ohm resistor = 101 v MAX on peaks.... or 40 vrms
Current through the 22 ohm resistor = 4.68A MAX.... or 1.82A RMS
Current flowing into 25 uf cap = 3.7 A max..... 1.58A RMS
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OK.... now with 22 ohm resistor REMOVED !!!
Vdc across load = 2820 vdc [ UNDER THE SAME 900 Ma LOAD] An
INCREASE of just 68 vdc ..... not a helluva big difference.
Current into 25 uf cap = 4.31 a MAX..... or 1.71 A RMS.
............................................................................
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OK.. here we increase the load to 2 A .... and NO resistor
2624 vdc under load of 2 A
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Now with the 22 ohm resistor.. and a 2A load.
2514 vdc under load of 2A A 110 vdc DROP.. with 22 ohm
resistor in the circuit. More of a difference here.
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OK.... now lets IN-crease the filter cap..from 25 uf..... up to 312 uf
+ .136 ohm TOTAL ESR [ ,017 ohm per cap, 8 x caps in series, caps
are CD 400 series... 2" diam x 4" long]
2581 vdc under load of 2A and 22 ohm resistor IN the circuit.
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OK... 312 uf filter cap and a load of 2A.... and NO 22 ohm
resistor.
2710 vdc under load of 2 A.... and the 22 ohm R is OUT of the circuit.
This is a 129 vdc improvement with the 22 ohm resistor
REMOVED.
BTW.... conduction time of pulses INTO the 312 uf cap is 2 msecs with
22 ohm resistor In the circuit... and 1.8 msecs with 22 ohm resistor
OUT of the circuit.
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### So with a run of the mill 3 kv supply......and sucking 900
ma... adding a 22 ohm resistor B4 the filter cap cost you aprx 68 vdc
drop. And it MIGHT be able to be used for step start.... since it takes
70 msecs to ramp up to max vdc.... on initial turn on. [ NO load..
except for the 800K eq resistor /bleeder [ 100k per cap] Dunno if it's
really worse the hassle of shorting out the 22 ohm resistor.. with a vac
relay... for a lousy 68 vdc increase.
Sri for the diatribe, it appears Mr. Garland, W8ZR is correct on all
accounts.
later......... Jim VE7RF
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