???
Ever here of a fuse with 60 volts ACROSS it? Come on... power is the
only thing that generates heat... this is either I^2 R or V^2 / R or
I*E... you can't get any of these to equal something without a
resistance... period.
________________________________________________
Kevin Vannorsdel IBM Arm Electronics Development
408-256-6492 Tie 276-6492 kv@... KF6YCI
Please respond to Electronics_101@...
To: Electronics_101@...
cc:
Subject: Re: [Electronics_101] Re: Fuses
It is correct that fuses are in units of Current.
Power(watts) is in units of (AMPS)Current and volts. POWER=VOLTS X
CURRENT
FUSES PROTECT CIRCUITS (IF SIZED CORRECTLY) WHEN THE Amps is sufficient
to
"blow" the fuses.
If fuses were sized in Power (watts) they would have to be rated for a
certain current, AND voltage and there are many combinations that one
could
come up with for a certain power rateing.
ie. (power =60watts} could be a current of 1A at 60 Volts, or 60amps
at
1 Volt, or 20Volts at 3 Amps. etc so it would not make sense to rate
them
using power (watts)
From: "Guillermo Brajovic" <guillermo.brajovic@...>
Reply-To: Electronics_101@...
To: Electronics_101@...
Subject: [Electronics_101] Re: Fuses
Date: Sat, 27 Oct 2001 22:35:23 -0000
Can anyone answer my original question - Why are fuses not rated in
units of power?
As fuses are used as overcurrent protection devices, the relevant
factor here is the CURRENT that the fuse will carry before melting.
Power is somewhat irrelevant here, as it would be an indirect way to
tell you the important parameter, the current capacity.
I cannot recall anyone designing a circuit saying "then, I want the
fuse to blow while it dissipates 10W or above", but " I want the the
fuse to blow while 10A or above go through this path".
Also, power alone is useless, you need also the resistance of the
fuse to calculate the current capacity, or the voltage drop across
the fuse.
Guillermo.
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