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Inverter Fuses - Amps and VOLTS?

H

Helpmeister

Jan 1, 1970
0
Maybe someone could give me a definitive answer on this:



In my car I was using a 300-watt power inverter which provides power by
being plugged into the cigarette lighter plug. The power inverter was doing
fine for years until I absent-mindedly plugged in a 500-watt electric teapot
recently and blew the fuse in the inverter.



The blown glass-type fuse that I removed had 15A imprinted on the side, but
when I searched for a 15-amp glass fuse replacement at the local electronic
store, I have a choice between a 32-volt 15-amp glass fuse and a 250-volt
15-amp glass fuse. The ubermensch in the electronic store experienced a
"duh" moment and ambled back off to his tar pit when asked about the
significance of the voltage difference, so I was none the wiser for his
valuable assistance. There doesn't seem to be any documentation or
reference anywhere, either with the inverter or on the Internet (that I can
find) that addresses this issue.



So, 32-volt vs. 250-volt - what's the essential difference and which do I
need in this case? Will 32-volt blow immediately once I plug anything into
the inverter, or will 250-volt NOT blow and wreck some piece of equipment
that the fuse is supposed to protect? Thoughts? Thanks in advance!
 
R

Rheilly Phoull

Jan 1, 1970
0
Helpmeister said:
Maybe someone could give me a definitive answer on this:



In my car I was using a 300-watt power inverter which provides power by
being plugged into the cigarette lighter plug. The power inverter was
doing
fine for years until I absent-mindedly plugged in a 500-watt electric
teapot
recently and blew the fuse in the inverter.



The blown glass-type fuse that I removed had 15A imprinted on the side,
but
when I searched for a 15-amp glass fuse replacement at the local
electronic
store, I have a choice between a 32-volt 15-amp glass fuse and a 250-volt
15-amp glass fuse. The ubermensch in the electronic store experienced a
"duh" moment and ambled back off to his tar pit when asked about the
significance of the voltage difference, so I was none the wiser for his
valuable assistance. There doesn't seem to be any documentation or
reference anywhere, either with the inverter or on the Internet (that I
can
find) that addresses this issue.



So, 32-volt vs. 250-volt - what's the essential difference and which do I
need in this case? Will 32-volt blow immediately once I plug anything
into
the inverter, or will 250-volt NOT blow and wreck some piece of equipment
that the fuse is supposed to protect? Thoughts? Thanks in advance!
Fuses are rated to the voltage of the circuit they protect. In this instance
you will need to determine which part of the inverter the fuse protects.
Sounds like the low voltage input from the current stated, so go for the
32volt if cheaper, the voltage rating does not affect the current the fuse
blows at so either will work OK.
 
J

John Popelish

Jan 1, 1970
0
Helpmeister said:
Maybe someone could give me a definitive answer on this:



In my car I was using a 300-watt power inverter which provides power by
being plugged into the cigarette lighter plug. The power inverter was doing
fine for years until I absent-mindedly plugged in a 500-watt electric teapot
recently and blew the fuse in the inverter.



The blown glass-type fuse that I removed had 15A imprinted on the side, but
when I searched for a 15-amp glass fuse replacement at the local electronic
store, I have a choice between a 32-volt 15-amp glass fuse and a 250-volt
15-amp glass fuse. The ubermensch in the electronic store experienced a
"duh" moment and ambled back off to his tar pit when asked about the
significance of the voltage difference, so I was none the wiser for his
valuable assistance. There doesn't seem to be any documentation or
reference anywhere, either with the inverter or on the Internet (that I can
find) that addresses this issue.



So, 32-volt vs. 250-volt - what's the essential difference and which do I
need in this case? Will 32-volt blow immediately once I plug anything into
the inverter, or will 250-volt NOT blow and wreck some piece of equipment
that the fuse is supposed to protect? Thoughts? Thanks in advance!

A fuse's voltage rating tells you how much voltage it can interrupt
when it blows. Since a 15 amp fuse would have to be on the 12 volt
side of the inverter, either rating will easily extinguish the arc
caused by the 14 volts or so from the battery.

Don't be too surprised if you discover that the fuse did not blow to
protect the inverter from damage, but to protect the wiring after the
inverter was destroyed by the overload.
 
C

CWatters

Jan 1, 1970
0
Helpmeister said:
Maybe someone could give me a definitive answer on this:
In my car I was using a 300-watt power inverter
The blown glass-type fuse that I removed had 15A imprinted on the side,

What voltage was marked on the one you took out and was it in the plug that
fits in the cigar skt?

Are you sure it's a 300W inverter?...

15A x 12V = 180W

What country are you in?

If the output is 220-240V (eg for the UK/Europe) could the fuse be a 1.5A (1
point 5 Amps) ?

1.5 x 230 = 345 W
 
I believe most inverters advertise their peak output power up front,
and then unobtrusively reveal their (much lower) continuous output
power somewhere in the manual. And since a "fast blow" fuse will
withstand twice its rated current for some time, it's possible that the
inverter can transmit 300W briefly with that fuse. A TV, for example,
can pull a surge current when you power it up before settling at a
lower level of power consumption.
 
M

mike

Jan 1, 1970
0
John said:
A fuse's voltage rating tells you how much voltage it can interrupt when
it blows. Since a 15 amp fuse would have to be on the 12 volt side of
the inverter, either rating will easily extinguish the arc caused by the
14 volts or so from the battery.

Never thought much about this before. If a 250V fuse were not different
in some way that was detrimental to the low voltage circuit, there'd be
no reason to have a 32V fuse. Is the 32V fuse lower resistance? Or
maybe it's just the added cost of the springs that insure the distance
between the ends of the blown 250V fuse?

mike

Don't be too surprised if you discover that the fuse did not blow to
protect the inverter from damage, but to protect the wiring after the
inverter was destroyed by the overload.



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C

CWatters

Jan 1, 1970
0
I believe most inverters advertise their peak output power up front,
and then unobtrusively reveal their (much lower) continuous output
power somewhere in the manual. And since a "fast blow" fuse will
withstand twice its rated current for some time, it's possible that the
inverter can transmit 300W briefly with that fuse. A TV, for example,
can pull a surge current when you power it up before settling at a
lower level of power consumption.

Which just makes a 500W kettle an even bigger overload :)
 
J

John Popelish

Jan 1, 1970
0
mike said:
John Popelish wrote:


Never thought much about this before. If a 250V fuse were not different
in some way that was detrimental to the low voltage circuit, there'd be
no reason to have a 32V fuse. Is the 32V fuse lower resistance? Or
maybe it's just the added cost of the springs that insure the distance
between the ends of the blown 250V fuse?

I am not an expert on fuse construction. It stands to reason that it
is easier to make a mechanism that is certain to block 32 volts than
it is to make one that blocks 250 volts. I think you should open a
few different kinds and see what you can discover about their
differences.
 
D

DBLEXPOSURE

Jan 1, 1970
0
John Popelish said:
I am not an expert on fuse construction. It stands to reason that it is
easier to make a mechanism that is certain to block 32 volts than it is to
make one that blocks 250 volts. I think you should open a few different
kinds and see what you can discover about their differences.


The voltage rating on a fuse comes into play the moment the fuse opens. If
a low voltage fuse is use in the place of a 120Volt or 250Volt fuse, the
fuse will arc across the gab for a longer period of time than would a fuse
of the appropriate voltage rating. Typically, it is not a problem to use a
fuse with a higher voltage rating in a low voltage application.
 
R

Rich Grise

Jan 1, 1970
0
The voltage rating on a fuse comes into play the moment the fuse opens. If
a low voltage fuse is use in the place of a 120Volt or 250Volt fuse, the
fuse will arc across the gab for a longer period of time than would a fuse
of the appropriate voltage rating. Typically, it is not a problem to use a
fuse with a higher voltage rating in a low voltage application.

I've seen 32 volt fuses literally explode on a 240V circuit, and blow
the holder cap half-way across the factory floor. Had to retrain the shop
gorillas...

Cheers!
Rich
 
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