[Milsurplus] [ARC5] Quieting A DC/DC Converter

[Peter Gottlieb]

I guess it depends.  I've seen fuses in power supplies open when a tantalum 
capacitor shorted on a rail.  Without the fuse the cap would likely burn the PCB 
or possibly start a fire.

The rule I heard was that the $50 transistor would blow to protect the 25 cent fuse.



On 1/21/2018 5:15 PM, Richard wrote:
>
> Understand that the primary purpose of fuses is not to protect internal 
> components, but to isolate the fault from the power source and not burn your 
> house down.  Further, fuses aren't fast.  they will blow "eventually" at 135% 
> of rating, (minutes to hours) about two minutes at 200%, and about five cycles 
> with a good short.
>
> Richard, AA1P
>
>
> On 01/21/2018 04:22 PM, Bob kb8tq wrote:
>> Hi
>>
>> The gotcha with fuses as protection for something like this is that the fuse 
>> is likely
>> to be protected by the inverter dying. Coming up with proper (high speed) 
>> protection
>> is something that can be done. It just adds cost ….
>>
>> Since this is a square wave, the transformer and how it interacts is *not* a 
>> simple thing.
>> Load removal may be an “interesting” event right along with shorts. Often 
>> things get
>> tuned with R/C networks to calm it all down. Again, not life or death. Just 
>> more parts
>> and a bit more time playing with the design.
>>
>> Bob
>>
>>> On Jan 21, 2018, at 3:26 PM, Military Wireless Museum <military1944 at aol.com 
>>> <mailto:military1944 at aol.com>> wrote:
>>>
>>> Subject: Re: [ARC5] [Milsurplus] Quieting A DC/DC Converter
>>> Hi
>>> Equally to the point:
>>> Are there enough people interested to fund a run of 50 or so transformers to 
>>> get the cost
>>> down out of the stratosphere?
>>> Also worth noting:
>>> The circuit we have been looking at is a full open loop square wave source. 
>>> There is no
>>> protection of any sort anywhere on the board. As it’s done right now, the 
>>> first time there
>>> is a short (or other fault) is the last time for that board. If you are 
>>> going to design from
>>> scratch, how much protection do you want to add?
>>> Bob
>>>
>>>
>>> I would be interested, depending on the cost of course.
>>>
>>> Fuses. I think any competent builder would fuse the input line and the 
>>> tranny feed.
>>>
>>> Ben.
>>>
>>>
>>>
>>>
>>
>>
>>
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>
>
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