Date: Sat, 8 Jan 2011 19:36:03 -0500
From: "Carl" <km1h@jeremy.mv.com>
Subject: Re: [Amps] Fuses
To: "James R Carr" <n7fcf@hctc.com>, "Roger \(K8RI\)"
<sub1@rogerhalstead.com>, <amps@contesting.com>
Message-ID: <01b501cbaf95$341b1890$6401a8c0@DAVES>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
Can you two get back to earth and keep it somewhat relative to ham amps in
the under 20KW range (-;
Carl
KM1H
King carl
## the basic concepts are still the same.. 'slightly' larger scale. Same
problems too....
huge back EMF, when opening off a fully loaded plate xfmr..esp if on rtty/fm.
## Now Rich Measures, and other's will say the HV fuse in the B+ line is not
required..and
that the 'follow on' current can easily be shut down with the fuses/breaker
in the 240 vac line,
[or some kind of current sense lead scheme that open's off the main contactor].
## If a HV fuse is used in the B+ line..just prior to the 50 ohm glitch R...
and a B+ to chassis
arc occurs [or anode to a chassis grnded grid] the 50 ohm glitch R ...LIMITS
the fault current
to a safe value. The HV fuse INTERRUPTS the fault current..a split second
later. The 240 vac
breaker/ fuses in the primary of the plate xfmr will never open. Ok, now you
don't have the back
EMF problem any more. I also use a 2nd HV fuse in one leg of the plate xfmr
sec..[ either leg].
Same deal, if the HV-AC fuse blows open, no back emf on the 240 vac primary
side of plate xfmr,
FWB is still protected, and so is the plate xfmr. I still use big, fused
mov's directly across the pri
of the plate xfmr.. and also from each side of the plate xfmr hot leg to
neutral...also fused. And
more movs directly across all contacts on the contactor.
later... Jim VE7RF
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