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Re: [Amps] Results from new PSUD... resistor b4 the B+ filter caps !

To: Jim.thom@telus.net, amps@contesting.com
Subject: Re: [Amps] Results from new PSUD... resistor b4 the B+ filter caps !
From: TexasRF@aol.com
Date: Thu, 11 Feb 2010 11:22:49 EST
List-post: <amps@contesting.com">mailto:amps@contesting.com>
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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