Calculation method of fuse

For high-current protection zones, the selected fuse should have the following characteristics:
Large capacity, usually tens to hundreds of amperes;
Able to withstand instantaneous large currents and large pulses;
High safety and reliability;
Relatively high ambient temperature;
Good mechanical properties.

Selection of fuse type

Choose the appropriate type according to the working environment, size restrictions, current characteristics, voltage characteristics and the connection method of the fuse. Generally, the high-voltage fuses of electric vehicles will use the American standard FWH, FWP and other series.

Determine the fuse parameters

Generally, the rated current value of the fuse is based on the value when the ambient temperature is 23±5°C. In order to meet the actual working conditions of electric vehicles, the rated current value needs to be corrected. The maximum allowable continuous load current can be calculated by the following formula

Ib = In·Kt·Ke·Kv·Kf·Kb

In the formula:

Ib ———Maximum allowable continuous load current;

In—the rated current of the fuse;

Kt temperature correction coefficient;

Ke-The thermal conductivity of the connected equipment;

Kv-air cooling correction factor;

Kf frequency correction coefficient;

Kb- the correction factor of the fuse box.

Through the above formula, the preliminary rated current of the fuse can be obtained. But under normal circumstances, In is a non-standard value. When selecting a model, please select a standard value greater than In.

Fuse parameter correction

The rated value of the fuse calculated by this formula is preliminary selection data. After the preliminary selection is completed, the rated current value of the fuse will be corrected according to the actual working condition data, such as the duration of the overload current, the magnitude of the current and the impact. Current duration, current amplitude and other factors are used for parameter correction.