Oh bless you your worthiness
----- Original Message -----
From: "Carl" <km1h@jeremy.mv.com>
To: "James R Carr" <n7fcf@hctc.com>; "Roger (K8RI)"
<sub1@rogerhalstead.com>; <amps@contesting.com>
Sent: Saturday, January 08, 2011 5:46 PM
Subject: Re: [Amps] Fuses
>I like it when the commoners react fast.
>
> You may carry on.
>
>
> ----- Original Message -----
> From: "James R Carr" <n7fcf@hctc.com>
> To: "Carl" <km1h@jeremy.mv.com>; "Roger (K8RI)" <sub1@rogerhalstead.com>;
> <amps@contesting.com>
> Sent: Saturday, January 08, 2011 8:09 PM
> Subject: Re: [Amps] Fuses
>
>
>> Excuse us your royal highness
>> ----- Original Message -----
>> From: "Carl" <km1h@jeremy.mv.com>
>> To: "James R Carr" <n7fcf@hctc.com>; "Roger (K8RI)"
>> <sub1@rogerhalstead.com>; <amps@contesting.com>
>> Sent: Saturday, January 08, 2011 4:36 PM
>> Subject: Re: [Amps] Fuses
>>
>>
>>> Can you two get back to earth and keep it somewhat relative to ham amps
>>> in the under 20KW range (-;
>>>
>>> Carl
>>> KM1H
>>>
>>>
>>> ----- Original Message -----
>>> From: "James R Carr" <n7fcf@hctc.com>
>>> To: "Roger (K8RI)" <sub1@rogerhalstead.com>; <amps@contesting.com>
>>> Sent: Saturday, January 08, 2011 7:21 PM
>>> Subject: Re: [Amps] Fuses
>>>
>>>
>>>> Down in prosser, WA about 30 years ago they had a problem with a
>>>> pottato
>>>> processing plant and a mechanic came running into the panel room and
>>>> before
>>>> anyone could stop him threw the main 480v 3 phase breaker. The plant
>>>> was
>>>> under full load with motors up the cazoo. When the back emf hit it blew
>>>> the
>>>> breaker out of the panel. The guy was lucky he wasn't hurt.
>>>> I retired in 2000 and there is a whole raft of devices that have come
>>>> on
>>>> line since.
>>>> Jim
>>>> N7FCF
>>>> ----- Original Message -----
>>>> From: "Roger (K8RI)" <sub1@rogerhalstead.com>
>>>> To: <amps@contesting.com>
>>>> Sent: Saturday, January 08, 2011 2:38 PM
>>>> Subject: Re: [Amps] Fuses
>>>>
>>>>
>>>>>
>>>>>
>>>>> On 1/8/2011 5:22 PM, James R Carr wrote:
>>>>>> Agreed, The first instant in time you have the full output of
>>>>>> Bonnyville
>>>>>> Dam
>>>>>> on the fault. But then the impedance of the system kicks in and
>>>>>> limits
>>>>>> it.
>>>>>> But still depending on the size of the utility transformer, it's
>>>>>> eficiency,
>>>>>> the length and size of the service conductors, you can still have
>>>>>> several
>>>>>> thousand amps at the main panel and down the line. About 20 25 years
>>>>>> ago
>>>>>> they had to increase the fault clearing ability all the breakers in
>>>>>> the
>>>>>> panels from 5000 amps to 20000 amps due to the increased use of low
>>>>>> loss
>>>>> Our mains weren't quite that large, but they were big...It's been too
>>>>> long for me to remember the actual size.
>>>>> They used magnetic quenching in arc chutes. They could open under
>>>>> full
>>>>> load without self destruction, BUT with big transformers down stream
>>>>> (Inductive loads) the "kick back" was so bad that reverse EMF would
>>>>> take
>>>>> out almost any thing attached to the line. So, if you blew one of the
>>>>> mains you knew it was going to be an expensive day.
>>>>>
>>>>> 73
>>>>>
>>>>> Roger (K8RI)
>>>>>> transformers by the utilities. basically the breaker can clear it
>>>>>> without
>>>>>> exploding. It probably will be terminally damaged though. I have seen
>>>>>> buss
>>>>>> bars twisted into pretsels by a dead short and a breaker that didn't
>>>>>> clear
>>>>>> quick enough.
>>>>>> Jim
>>>>>> N7FCF
>>>>>> ----- Original Message -----
>>>>>> From: "Jim Thomson"<jim.thom@telus.net>
>>>>>> To:<amps@contesting.com>
>>>>>> Sent: Saturday, January 08, 2011 2:18 AM
>>>>>> Subject: [Amps] Fuses
>>>>>>
>>>>>>
>>>>>>> Date: Sat, 8 Jan 2011 08:34:30 +0000
>>>>>>> From: Ian White GM3SEK<gm3sek@ifwtech.co.uk>
>>>>>>> Subject: Re: [Amps] Fuses
>>>>>>>
>>>>>>> James R Carr wrote:
>>>>>>>> Where pray tell do you get a hydraulic breaker? I have installed
>>>>>>>> several thousand over the years but have yet to see one filled with
>>>>>>>> oil. As for current limiting devices, the fastest breaker will hold
>>>>>>>> in
>>>>>>>> for three to seven full cycles. To be current limiting, a fuse has
>>>>>>>> to
>>>>>>>> clear in less
>>>>>>>> than 1/2 cycle.
>>>>>>> A fuse provides NO current limiting until it blows; and a breaker
>>>>>>> provides NO current limiting until it breaks.
>>>>>>>
>>>>>>> A lot of damage can be done in those first few milliseconds, which
>>>>>>> is
>>>>>>> why the fuse/breaker is only PART of the solution.
>>>>>>>
>>>>>>> We always need a surge limiting resistor in the B+ as well, to
>>>>>>> provide
>>>>>>> instantaneous current limiting until the fuse/breaker takes over and
>>>>>>> finally breaks the circuit.
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>>
>>>>>>> 73 from Ian GM3SEK
>>>>>>> http://www.ifwtech.co.uk/g3sek
>>>>>>>
>>>>>>> ## Agreed. The purpose of the mag-hydraulic breaker is [A] handy
>>>>>>> dandy
>>>>>>> way of opening off the 240 v line, without having to kill the
>>>>>>> dedicated
>>>>>>> breaker in the
>>>>>>> main 200A panel. [B] eliminate any follow on current.
>>>>>>>
>>>>>>> ## On my latest 7700 vdc supply, I use a Buss HVU series, sand
>>>>>>> filled
>>>>>>> HV fuse..rated at 3A..in series
>>>>>>> with the B+ lead. The HV fuse gets inserted just prior to the kw
>>>>>>> rated
>>>>>>> glitch R, which consists of 4 x
>>>>>>> parallel globar type AS energy absorbing type resistor's, 1.5"
>>>>>>> diam x
>>>>>>> 18' long. [ 4 x 200 ohm in parallel= 50 ohms]
>>>>>>> 7700/50 ohms = 154A. max fault current. Now 154 A of fault
>>>>>>> current,
>>>>>>> flowing through a 3 A rated
>>>>>>> fuse, will open VERY fast. [ the fuse is running at 5100% of it's
>>>>>>> rating]. I use a 50 ohm glitch R on the
>>>>>>> smaller supplies as well... with the provisio that a smaller rated
>>>>>>> HV
>>>>>>> fuse
>>>>>>> is used..like 1A, etc.
>>>>>>>
>>>>>>> ## I also use a 2nd Buss HV fuse, in the sec of the plate xfmr,
>>>>>>> [one
>>>>>>> leg
>>>>>>> only], between sec and input to
>>>>>>> FWB. In normal operation, with any B+ to chassis fault, the B+ HV
>>>>>>> fuse
>>>>>>> alway's blows open 1st..so the
>>>>>>> breaker used in the 240 v line is sorta a moot point. That B+
>>>>>>> fuse
>>>>>>> concept has been tested 34 x times
>>>>>>> now, and nothing ever happens..except a blown HV fuse. Once, some
>>>>>>> of
>>>>>>> the
>>>>>>> blown HV fuses were
>>>>>>> 'refurbished' with a single strand, soldered on the outside..and
>>>>>>> wrapped
>>>>>>> with 88 tape. In one case, the
>>>>>>> wire ga of the single strand refurbished job was too big.. and the
>>>>>>> end
>>>>>>> result was the parallel pair of 100
>>>>>>> ohm, 225 W- WW's were literally incinerated, burnt to a crisp. That
>>>>>>> was
>>>>>>> with a 165 uf filter cap..and a 253 lb
>>>>>>> dahl hypersil xfmr. That particular glitch R was replaced with 4
>>>>>>> parallel 200 ohm, 225 W, wirewounds
>>>>>>> [ $12.00 each, from mouser],and the correct size HV fuse. Zero
>>>>>>> problems
>>>>>>> since then, and you can literally
>>>>>>> cro-bar it all day long. I would not trust any of these glitch R's,
>>>>>>> even
>>>>>>> big ones..without a prior series HV fuse,
>>>>>>> not with big uf caps, huge amount's of joules involved, and then
>>>>>>> trying
>>>>>>> to
>>>>>>> rely on a breaker [ or even the
>>>>>>> 2nd HV AC fuse].
>>>>>>>
>>>>>>> ## In one instance, one of the hv lytics [ 3900 uf @ 450 vdc]
>>>>>>> towards
>>>>>>> the hot end of the string, arced through a
>>>>>>> crack in the plywood, and launched itself. Since the fault was
>>>>>>> before
>>>>>>> the B+ fuse.... the 2nd HV fuse blew.
>>>>>>> [ the one located between sec of xfmr and FWB]. The 96 x 6A10's
>>>>>>> in
>>>>>>> the
>>>>>>> FWB were not damaged. In 2 x instances the
>>>>>>> 240 vac breaker popped open. Once when a screw removed from a 6"
>>>>>>> fan..and
>>>>>>> the AL fan swung down like a pendulum
>>>>>>> and hit one side of the 240 vac buss. [ and blew a chunk out of the
>>>>>>> fan
>>>>>>> casing]. The 2nd time was a B+ fault.
>>>>>>>
>>>>>>> ## I use a simple 50 ohm-50W WW on my L4B's..with the stock
>>>>>>> drake HV
>>>>>>> B+ fuse. [ consist of a .82 ohm, 1 watt carbon R ].
>>>>>>> The stock .82 Ohm R always blows cleanly in 1/2. I have only had
>>>>>>> 2
>>>>>>> x
>>>>>>> ever blow open since 1977.
>>>>>>>
>>>>>>> later... Jim VE7RF
>>>>>>> _______________________________________________
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>>>>>>> http://lists.contesting.com/mailman/listinfo/amps
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>>>>>>
>>>>>
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>
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