1. Definition and working principle of fuses
Fuse, also known as current fuse, is a component that can automatically melt and cut off the current when the current abnormally rises to a certain height and temperature, thereby protecting the safe operation of the circuit. Its basic structure includes three parts: fuse, electrode and bracket. When current flows through the conductor, heat is generated due to the certain resistance of the conductor. When the current rises abnormally, the heat generated is enough to melt the fuse fuse, thereby cutting off the circuit and preventing equipment damage or fire and other safety accidents.
2. The role of fuses in battery energy storage systems
Circuit protection: Fuse is a circuit protection component in battery energy storage systems. When the current in the battery energy storage system exceeds the rated value, the fuse will quickly melt and cut off the circuit, thereby preventing equipment damage or fire and other safety accidents.
Secondary protection: In the battery energy storage system, the battery management system usually manages and controls the battery pack, including battery charging, discharging, temperature control, etc. However, in order to further improve the safety of the system, a secondary protection is usually added on the basis of the battery management system, that is, a fuse is used. In this way, even if the battery management system fails, the fuse can still play a protective role.
3. Types and selection of fuses
Type: Fuses can be divided into overcurrent protection and overheating protection according to the protection form; according to the melting speed, they can be divided into extra slow fuses (TT), slow fuses (T), medium fuses (M), fast fuses (F) and extra fast fuses (FF). In battery energy storage systems, it is usually necessary to select the appropriate fuse type according to the specific needs and characteristics of the system.
Selection: When selecting a fuse, factors such as its rated current, melting speed, and operating environment temperature need to be considered. The rated current should be greater than or equal to the normal operating current of the battery energy storage system, but less than the possible fault current. The melting speed needs to be determined based on the fault response time and safety requirements of the system. In addition, the operating environment temperature of the fuse needs to be considered to ensure that it will not be mistakenly melted under normal working conditions.
4. Application examples
Taking lithium-ion battery packs as an example, three-terminal fuses are usually used as secondary protection components. When the battery pack is exposed to risks such as overcurrent and overvoltage, the three-terminal fuse can be activated in time, effectively reducing the fire and explosion caused by overcharging, overdischarging, short circuit and other faults of lithium-ion batteries. The three-terminal fuse contains three terminals, two fuses made of alloy metal are connected in series, which can be melted in the event of overcurrent or short circuit; the middle series heater, its function is to form a series circuit with the MOSFET in the circuit. When the system detects that the battery is overvoltage, the MOSFET is turned on and the heater starts to heat, thereby burning the fuse and cutting off the circuit.
