1.Determination of load type

Loads include continuous loads, intermittent loads and special loads.
Continuous load: The load generated by the current flowing continuously from the time the switch is turned on until it is turned off is called a continuous load.
Intermittent load: After the switch is opened, when the hand is released or automatically closed after a period of time, only a short period of time during the operation of the current flow load is called intermittent load.
Special loads:Loads other than continuous loads and intermittent loads, such as lights and turn signals. The load current curves corresponding to continuous loads and intermittent loads are shown in the figure below.

2.Determination of fuse type

The fuse type is determined according to the type of load and the size of the load current.
(1) Selection of fast blowing fuses
Resistive loads are generally continuous loads, usually using fast blowing fuses, such as various control modules, lighting systems, etc.
For motor-type inductive loads, if the melting time exceeds the peak current time of the load, a fast blowing fuse can be selected, and if this cannot be met, a slow blowing fuse is required.
When the load is a small current load (within 20A), choose a fast blow fuse.
When the load is a short time pulse current load, use a fast blow fuse.
Commonly used Mini fuses, its specifications 2 ~ 30A, applicable to the current does not exceed 30A load, such as internal and external lamps, air race, etc..

(2) Use of slow blowing fuses
Generally speaking, motors, valves and other inductive loads use slow blow fuses.
When the load is a high-current load (more than 20A), the use of slow blowing fuses, such as after defrosting.
Slow blow fuses are used for long time pulse loads, such as glass lifting motors and other motorized loads.
Slow blow fuses are used for locking current loads, such as wiper motors, door lock motors, and power seat loads.
Slow blow fuses are commonly used as JCASE fuses, MIDI fuses and Mega fuses.
JCASE fuse size 20~60A is mainly used for high current loads such as rear exhaust, air-conditioning blower, cooling fan, etc.
Midi fuse specifications 30 ~ 200A, applicable to the current does not exceed 200A loads, such as battery fuse box at the large fuse; Meqa fuse specifications 40 ~ 500A, the highest rated current products on the market, applicable to high-current and high pulse circuit protection. Such as battery, generator protection.

Trends in fuse selection

Fuse selection, in addition to considering the type of load and the size of the load current, but also need to consider the development of the fuse. It is necessary to combine the trend of fuse development to choose the type of fuse comprehensively.