Fuses – Overview


Do you know your fuses?

A fuse is a device that, by the melting of its element, opens an electrical circuit. The melting of the element occurs when the electrical current exceeds a specified level for a specified time. This action is irreversible and the fuse must be replaced after the circuit malfunction is repaired.
A fuse is a temperature-sensitive device. This means that changes in ambient temperature, external heat sources (such as other fuses) and external heat sinks (such as conducting wires) affect the fuse.
Fuse ratings are based on an ambient temperature of 77°F. Higher ambient temperatures will lower the effective fuse rating, and the fuse will open quicker for a given overload current.

Autofuse (ATO) & Minifuse

Blow times at % of rated current – at 77°F
Amp Rating
100%
135%
200%
600%
Color
Min (hours)
Min (sec)
Max (sec)
Min (sec)
Max (sec)
Max (sec)
5A
Tan
100
.75
600
.15
5
.1
7.5A
Brown
100
.75
600
.15
5
.1
10A
Red
100
.75
600
.15
5
.1
15A
Blue
100
.75
600
.15
5
.1
20A
Yellow
100
.75
600
.15
5
.1
25A
White
100
.75
600
.15
5
.1
30A
Green
100
.75
600
.15
5
.1

Maxifuse
Unlike previous high current circuit protection devices (e.g.: fusible links) the Maxifuse was designed to protect cables from both direct short circuits and resistive short circuits, without damaging the device itself. This is due to the higher temperature insulating materials used to house the Maxifuse element and the element design. Compared to Minifuse, Maxifuse opening times are longer.

Blow times at % of rated current – at 77°F

Amp Rating

100%
135%
200%
600%
Color
Min (hours)
Min (sec)
Max (sec)
Min (sec)
Max (sec)
Max (sec)
20A
Yellow
100
60
1800
4
20
1
25A
Gray
100
60
1800
4
20
1
30A
Green
100
60
1800
6
20
1
40A
Amber
100
60
1800
8
20
1
50A
Red
100
60
1800
10
20
1
60A
Blue
100
60
1800
15
20
1

Megafuse
The Megafuse is designed for high current protection of the battery/alternator system. It has a bolt-down design to facilitate easy installation and replacement. Similar to the Maxifuse, the Megafuse is engineered with time delayed characteristics to allow for high in-rush currents.

Amp Rating
Blow times at % of rated current – at 77°F
100%
135%
200%
600%
Min (hours)
Min (sec)
Min (sec)
Min (sec)
Max (sec)
Max (sec)
125A
4
120
1800
1
15
1
175A
4
120
1800
1
15
1