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
>>>>> _______________________________________________
>>>>> Amps mailing list
>>>>> Amps@contesting.com
>>>>> http://lists.contesting.com/mailman/listinfo/amps
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