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Re: [Amps] HV rectifier strings - to bypass or not?

To: "Carl" <km1h@jeremy.mv.com>, <garyschafer@comcast.net>, <amps@contesting.com>
Subject: Re: [Amps] HV rectifier strings - to bypass or not?
From: "Jim Thomson" <jim.thom@telus.net>
Date: Sun, 31 Oct 2010 16:56:29 -0700
List-post: <amps@contesting.com">mailto:amps@contesting.com>

--------------------------------------------------
From: "Carl" <km1h@jeremy.mv.com>
Sent: Sunday, October 31, 2010 6:38 AM
To: <garyschafer@comcast.net>; "'Jim Thomson'" <jim.thom@telus.net>; 
<amps@contesting.com>
Subject: Re: [Amps] HV rectifier strings - to bypass or not?

> Im telling you. At times, especially during storms, there will be 
> transients. Id also hate to see the transients from a sudden power failure 
> where the power kicks off and back on as a pole breaker trips and resets. 
> This is a rather normal occurance around here caused by wind or a drunk.
>
> Carl
> KM1H

###  I agree with this.  Back in 1988, at the Telco office I worked in, the 
3 phase power
all went off-on-off-on-off-on...all  within 5 seconds. This was a power co 
problem, no windstorms.
The surges and spikes  from the above  took out 8 x dc-dc power supplies, 
they all had popped their
40A breakers!   Each of the  40 x  dc-dc power supplies consisted  of -52.8 
vdc  going into em [via a
7A 3agc type fuse]  and the output was +5vdc @ 40A CCS , [with a 40A 
breaker].  Neither the the 7A
fuse on the input, nor the 40A on the output were fast types either.

 The -52.8vdc  comes from the UPS setup, which in any Telco, consists of 
paralleled -52.8vdc rectifiers
[pwr supplies],typ 100-800A variety, all feeding a common buss.  24 x 189 kg 
batteries are strung in series,
 [12 above 12], typ 1900-2500 AH lead acid types, with just over 2 vdc per 
battery [aka....cell].  1-12 strings
of batteries are all in parallel via the common buss.    No fuses between 
each string of batteries and the buss.
208 vac 3 phase  [and sometimes 480 vac]  is fed to the inputs of the 
paralleled  rectifiers.

## The surge / spike  had gotten past the huge Josyln  [fused]  MOV's  [all 
3 x are wired phase to neutral].   The spike
had gotten past the pair of -52.8vdc @ 200 A power supplies, past the string 
of batteries... and then into the -52.8dc
to + 5vdc converters....and blew their slo-output breakers.   This was the 
only instance I saw this happen... once in 34 yrs.
Now if ur in an area, like Carl, with commercial AC pwr coming and going,  I 
can see this being a big problem.  Talk to any
electrician who works in a pulp mill, and they will give you an earful 
about spikes, surges and transients.

##  another method you will see in the Orr books is a RC  snubber, directly 
across the sec of the plate xfmr.  I tried the
snubber across the sec of  my pole pig.  I don't know how effective it is. 
Another method is putting a  .0047uf or .01uf
cap across the sec of the plate xfmr.   Locating the snubber / cap  across 
the primary of the plate xfmr may be another option,
and probably a better one.

Jim  VE7RF.




>
>
> ----- Original Message ----- 
> From: "Gary Schafer" <garyschafer@comcast.net>
> To: "'Carl'" <km1h@jeremy.mv.com>; "'Jim Thomson'" <jim.thom@telus.net>; 
> <amps@contesting.com>
> Sent: Saturday, October 30, 2010 10:39 PM
> Subject: RE: [Amps] HV rectifier strings - to bypass or not?
>
>
>> Are you telling us that you see power line transients across the output 
>> of
>> your 3000 volt power supply?
>>
>> 73
>> Gary K4FMX
>>
>>> -----Original Message-----
>>> From: Carl [mailto:km1h@jeremy.mv.com]
>>> Sent: Saturday, October 30, 2010 9:15 PM
>>> To: garyschafer@comcast.net; 'Jim Thomson'; amps@contesting.com
>>> Subject: Re: [Amps] HV rectifier strings - to bypass or not?
>>>
>>> What mighty spikes? What is the rise time, duration and PRR?
>>>
>>> Have you actually watched a 3000-5000VDC PS on a scope?
>>>
>>> Carl
>>> KM1H
>>>
>>>
>>> ----- Original Message -----
>>> From: "Gary Schafer" <garyschafer@comcast.net>
>>> To: "'Carl'" <km1h@jeremy.mv.com>; "'Jim Thomson'" <jim.thom@telus.net>;
>>> <amps@contesting.com>
>>> Sent: Saturday, October 30, 2010 9:51 PM
>>> Subject: RE: [Amps] HV rectifier strings - to bypass or not?
>>>
>>>
>>> > Why not? The output of the rectifiers provide some mighty spikes of
>>> their
>>> > own. The capacitors handle it just fine.
>>> >
>>> > 73
>>> > Gary  K4FMX
>>>
>>>
>>>
>>>
>>> >
>>> >> -----Original Message-----
>>> >> From: Carl [mailto:km1h@jeremy.mv.com]
>>> >> Sent: Saturday, October 30, 2010 8:44 PM
>>> >> To: garyschafer@comcast.net; 'Jim Thomson'; amps@contesting.com
>>> >> Subject: Re: [Amps] HV rectifier strings - to bypass or not?
>>> >>
>>> >> You dont want intense line spikes going thru electrolytics.
>>> >>
>>> >> Carl
>>> >> KM1H
>>> >>
>>> >>
>>> >> ----- Original Message -----
>>> >> From: "Gary Schafer" <garyschafer@comcast.net>
>>> >> To: "'Jim Thomson'" <jim.thom@telus.net>; <amps@contesting.com>
>>> >> Sent: Saturday, October 30, 2010 9:28 PM
>>> >> Subject: Re: [Amps] HV rectifier strings - to bypass or not?
>>> >>
>>> >>
>>> >> > Why place a capacitor across each diode string on a full wave 
>>> >> > bridge?
>>> >> The
>>> >> > filter capacitor is always across the transformer secondary.
>>> >> >
>>> >> > 73
>>> >> > Gary  K4FMX
>>> >> >
>>> >> >> -----Original Message-----
>>> >> >> From: amps-bounces@contesting.com [mailto:amps-
>>> bounces@contesting.com]
>>> >> On
>>> >> >> Behalf Of Jim Thomson
>>> >> >> Sent: Saturday, October 30, 2010 7:58 PM
>>> >> >> To: amps@contesting.com
>>> >> >> Subject: [Amps] HV rectifier strings - to bypass or not?
>>> >> >>
>>> >> >>
>>> >> >> ##  KM1H  came up with a better method... and that's to install 
>>> >> >> one
>>> HV
>>> >> >> disc ceramic
>>> >> >> across each leg.....so 4 x caps in all.    The purpose of these 4 
>>> >> >> x
>>> >> caps
>>> >> >> is to  bypass any
>>> >> >> junk/transients coming in off the street. Of course the V rating 
>>> >> >> has
>>> >> >> to
>>> >> >> be
>>> >> >> high if a single
>>> >> >> cap is used.  You can get disc ceramic caps in 4700 pf @  10/15 kv
>>> >> >> variety.  [ Ceramite brand,
>>> >> >> sold by mouser+ henry radio still has em].   IF  .01 uf caps 
>>> >> >> [10,000
>>> >> pf]
>>> >> >> installed across each diode,
>>> >> >> and 8 x diodes used, you only have 10,000/8 =   1250 pf 
>>> >> >> effectively
>>> >> >> across each leg.  If individual
>>> >> >> caps used, .02uf @ 1 kv would be better.    IMO... 4 x big caps, 
>>> >> >> one
>>> >> per
>>> >> >> leg, is more effective, and
>>> >> >> messier than 32 x  caps.
>>> >> >>
>>> >> >
>>> >> > _______________________________________________
>>> >> > Amps mailing list
>>> >> > Amps@contesting.com
>>> >> > http://lists.contesting.com/mailman/listinfo/amps
>>> >
>>> >
>>
>>
>
> 

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