resettable fuse

[Mochuelo]

Hi,

Does anyone know of a resettable fuse with these characteristics?
- Trips to off with 1.5 A in 1 s or less (at 25 şC).
- Stands 30 V in the off state.

Thank you.

 

[Roger Hamlett]

"Mochuelo" <cucafera@RE_MO_VE_THIStelefonica.net> wrote in message
news:2fq4f1lq1i2dlnec3vpcapthvdahhl894u@4ax.com...

Hi,

Does anyone know of a resettable fuse with these characteristics?
- Trips to off with 1.5 A in 1 s or less (at 25 şC).
- Stands 30 V in the off state.

Thank you.
What you don't say is how much it has to carry as hold current?. Some

polymer fuses will do this, but only the versions rated for perhaps 1/4A
continuously, will get the switching speed you require. The closer the
continuous current is to the trip current, the slower the response to that
trip current. You also don't say whether 'resettable', means self
resetting, or with a button?. Remember that you can make a fuse like this
act very quickly (or at least get rid of the power to the circuit
quickly), by having a thyistor crowbar, operated by an overcurrent
detector, which then shorts out the supply, and blows the fuse. This only
clears, when the supply is broken.

Best Wishes

 

[Mochuelo]

On Thu, 04 Aug 2005 20:58:37 GMT, "Roger Hamlett"
<rogerspamignored@ttelmah.demon.co.uk> wrote:

"Mochuelo" <cucafera@RE_MO_VE_THIStelefonica.net> wrote in message
news:2fq4f1lq1i2dlnec3vpcapthvdahhl894u@4ax.com...
Hi,

Does anyone know of a resettable fuse with these characteristics?
- Trips to off with 1.5 A in 1 s or less (at 25 şC).
- Stands 30 V in the off state.

Thank you.
What you don't say is how much it has to carry as hold current?.

True. In fact, I have never used them, and I had just started reading
some datasheets when I posted my message.

The fuse needs to hold 0.7 A without tripping. I guess that, as you
say, it is going to be difficult to react in such a short time to such
a small relative change (1.5 / 0.7 (just 2x)).

Some
polymer fuses will do this, but only the versions rated for perhaps 1/4A
continuously, will get the switching speed you require. The closer the
continuous current is to the trip current, the slower the response to that
trip current. You also don't say whether 'resettable', means self
resetting, or with a button?.

I was thinking of self resetting.

Remember that you can make a fuse like this
act very quickly (or at least get rid of the power to the circuit
quickly), by having a thyistor crowbar, operated by an overcurrent
detector, which then shorts out the supply, and blows the fuse. This only
clears, when the supply is broken.

Best Wishes

Thanks.