For high current protection zones, the selected fuses should have the following properties:
①Large capacity, usually tens to hundreds of A; ②Can withstand instantaneous high current and high pulse; ③High reliability; ④The operating ambient temperature is relatively high ; ⑤ Good mechanical properties.
1. Selection of fuse type
Choose the appropriate type according to the working environment of the fuse, size restrictions, current characteristics, voltage characteristics, connection methods, etc. Usually electric vehicle high-voltage fuses will use American standard FWH, FWP and other series.
2. Determination of fuse parameters
Usually, the rated current value of the fuse is based on the value when the ambient temperature is 23±5 ℃. 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 with the following formula
In the formula:
Ib——the maximum allowable continuous load current;
In — the rated current of the fuse;
Kt——temperature correction factor;
Ke——the heat conduction factor of the connecting device;
Kv——air cooling correction factor;
Kf——frequency correction factor;
Kb——Fuse case correction factor.
Through the above formula, a preliminary rated current of the fuse can be obtained. But in general, In is a non-standard value. When selecting a model, you can choose the standard value that is greater than In.
3. Correction of fuse parameters
The rated value of the fuse calculated by the formula is a preliminary selection data. After the preliminary selection is completed, the rated current value of the fuse is corrected according to the actual operating condition data, such as the duration of the overload current, the magnitude of the current, the impact Parameters such as current duration, current size and other factors are corrected.
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