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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>>>>
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