Fuse question

H

Harry Muscle

Guest
If I want a fuse to blow at 2A, what size do I need to buy? I'm assuming
fuses have a little bit of safety, so that a 2A fuse won't blow till say
2.5A ... hence my question ... if I want a fuse to actually blow at 2A, what
rating do I get?

Thanks,
Harry




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Harry Muscle wrote:

If I want a fuse to blow at 2A, what size do I need to buy? I'm assuming
fuses have a little bit of safety, so that a 2A fuse won't blow till say
2.5A ... hence my question ... if I want a fuse to actually blow at 2A,
what rating do I get?

2A. The only safety there is is whether it's slow-blow or fast blow. I
Click to expand...
think that's probably where your confusion is coming from.

--Russell

--
Russell Miller
Somewhere near Sioux City, Iowa
Freelance computer programmer/administrator, pianist, and generally nice
guy.
 
"Russell Miller" <rmiller@duskglow.com> wrote in message
news:urkEb.18385$In6.14377@news02.roc.ny...
Harry Muscle wrote:

If I want a fuse to blow at 2A, what size do I need to buy? I'm
assuming
fuses have a little bit of safety, so that a 2A fuse won't blow till say
2.5A ... hence my question ... if I want a fuse to actually blow at 2A,
what rating do I get?

2A. The only safety there is is whether it's slow-blow or fast blow. I
think that's probably where your confusion is coming from.

--Russell

--
Russell Miller
Somewhere near Sioux City, Iowa
Freelance computer programmer/administrator, pianist, and generally nice
guy.
Click to expand...
How slow or how fast are we usually talking? Any standard recommendations
when it comes to installing a fu from of a transformer? It's rated at
250VA, but I don't every expect to reach more than 150VA.

Thanks,
Harry




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Harry Muscle wrote:

How slow or how fast are we usually talking? Any standard recommendations
when it comes to installing a fu from of a transformer? It's rated
at 250VA, but I don't every expect to reach more than 150VA.

The point of a slow blow fuse is to allow temporary current overages, such
Click to expand...
as when a motor starts. A fast blow fuse will blow instantly.

--Russell

Thanks,
Harry




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Click to expand...
--
Russell Miller
Somewhere near Sioux City, Iowa
Freelance computer programmer/administrator, pianist, and generally nice
guy.
 
"Harry Muscle" <fake@AT@e-mail.com> wrote in message
news:3fe1d51d$1_1@corp.newsgroups.com...
"Russell Miller" <rmiller@duskglow.com> wrote in message
news:urkEb.18385$In6.14377@news02.roc.ny...
Harry Muscle wrote:

If I want a fuse to blow at 2A, what size do I need to buy? I'm
assuming
fuses have a little bit of safety, so that a 2A fuse won't blow till
say
2.5A ... hence my question ... if I want a fuse to actually blow at
2A,
what rating do I get?

2A. The only safety there is is whether it's slow-blow or fast blow. I
think that's probably where your confusion is coming from.

--Russell

--
Russell Miller
Somewhere near Sioux City, Iowa
Freelance computer programmer/administrator, pianist, and generally nice
guy.

How slow or how fast are we usually talking? Any standard recommendations
when it comes to installing a fu from of a transformer? It's rated
at
250VA, but I don't every expect to reach more than 150VA.

Thanks,
Harry




-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
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Click to expand...
A good rule of thumb is motors, heaters and transformers use slow blow and
semicondutors use fast blow. This is an oversimplification, but I think
that's all you are asking at this point.....good luck....Ross
 
Harry Muscle wrote:
If I want a fuse to blow at 2A, what size do I need to buy? I'm assuming
fuses have a little bit of safety, so that a 2A fuse won't blow till say
2.5A ... hence my question ... if I want a fuse to actually blow at 2A, what
rating do I get?
Click to expand...
The fuse current rating is normally the largest current that is
guaranteed not blow the fuse under some specified ambient temperature
for some rather long (specified) period of time. Usually some
specific overload is required to guarantee opening in some specified
period of time. A common one is 10 seconds or less with a 100%
overload from a cold start. If the fuse is operated for long enough
at rated current for it to reach thermal equilibrium, the opening time
is significantly shortened. You need the actual fuse data sheet to
nail down any specific example.

A fuse is not generally a precision current limiting device, but a
rough protection that limits the spread of damage in the event of a
severe overload.

--
John Popelish
 
Try this for a good primer on fuses:

http://www.littelfuse.com/PDFs/EDG_Cat/Fuseology.pdf
 
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