[Amps] HV rectifier strings - to bypass or not?
Jim Thomson
jim.thom at telus.net
Sun Oct 31 16:56:29 PDT 2010
--------------------------------------------------
From: "Carl" <km1h at jeremy.mv.com>
Sent: Sunday, October 31, 2010 6:38 AM
To: <garyschafer at comcast.net>; "'Jim Thomson'" <jim.thom at telus.net>;
<amps at 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 at comcast.net>
> To: "'Carl'" <km1h at jeremy.mv.com>; "'Jim Thomson'" <jim.thom at telus.net>;
> <amps at 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 at jeremy.mv.com]
>>> Sent: Saturday, October 30, 2010 9:15 PM
>>> To: garyschafer at comcast.net; 'Jim Thomson'; amps at 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 at comcast.net>
>>> To: "'Carl'" <km1h at jeremy.mv.com>; "'Jim Thomson'" <jim.thom at telus.net>;
>>> <amps at 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 at jeremy.mv.com]
>>> >> Sent: Saturday, October 30, 2010 8:44 PM
>>> >> To: garyschafer at comcast.net; 'Jim Thomson'; amps at 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 at comcast.net>
>>> >> To: "'Jim Thomson'" <jim.thom at telus.net>; <amps at 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 at contesting.com [mailto:amps-
>>> bounces at contesting.com]
>>> >> On
>>> >> >> Behalf Of Jim Thomson
>>> >> >> Sent: Saturday, October 30, 2010 7:58 PM
>>> >> >> To: amps at 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 at contesting.com
>>> >> > http://lists.contesting.com/mailman/listinfo/amps
>>> >
>>> >
>>
>>
>
>
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