[Amps] Fuses

Carl km1h at jeremy.mv.com
Sat Jan 8 19:00:10 PST 2011


Never mind the blessings, just send money or your first born.


----- Original Message ----- 
From: "James R Carr" <n7fcf at hctc.com>
To: "Carl" <km1h at jeremy.mv.com>; "Roger (K8RI)" <sub1 at rogerhalstead.com>; 
<amps at contesting.com>
Sent: Saturday, January 08, 2011 9:32 PM
Subject: Re: [Amps] Fuses


> Oh bless you your worthiness
> ----- Original Message ----- 
> From: "Carl" <km1h at jeremy.mv.com>
> To: "James R Carr" <n7fcf at hctc.com>; "Roger (K8RI)" 
> <sub1 at rogerhalstead.com>; <amps at 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 at hctc.com>
>> To: "Carl" <km1h at jeremy.mv.com>; "Roger (K8RI)" <sub1 at rogerhalstead.com>; 
>> <amps at contesting.com>
>> Sent: Saturday, January 08, 2011 8:09 PM
>> Subject: Re: [Amps] Fuses
>>
>>
>>> Excuse us your royal highness
>>> ----- Original Message ----- 
>>> From: "Carl" <km1h at jeremy.mv.com>
>>> To: "James R Carr" <n7fcf at hctc.com>; "Roger (K8RI)" 
>>> <sub1 at rogerhalstead.com>; <amps at 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 at hctc.com>
>>>> To: "Roger (K8RI)" <sub1 at rogerhalstead.com>; <amps at 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 at rogerhalstead.com>
>>>>> To: <amps at 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 at telus.net>
>>>>>>> To:<amps at 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 at 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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>>>>>
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>>>>
>>>
>>
> 



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