Electric vehicle fuse is a device specially designed for circuit protection of electric vehicle. Its core function is to block abnormal current through the fuse and prevent damage to the electrical system. In EV systems, they have three main functions:
I.short-circuit protection, overload protection and fault isolation.
Definition and working principle Electric vehicle fuse belongs to the category of new energy fuses and is a passive protective element. They work based on the thermal effect of current. When the current in the circuit exceeds the set value, the fusible element inside the fuse (usually metal with a low melting point) melts as heat accumulation, interrupting the circuit. This process is usually completed in milliseconds, effectively preventing potential equipment damage or fire hazards due to the continuous current flow.
II. Short circuit protection In the high voltage circuit of an electric vehicle, a short circuit failure can lead to a sudden and rapid increase in current, generate tremendous heat, damage electrical equipment, or even cause a fire. When a short circuit occurs, the fuse can quickly interrupt the circuit. For example, when a high-voltage wire harness shortens due to aging or wear, the fuse immediately melts to prevent short-circuit current from damaging the electrical system.
Overload Protection: Activating multiple high-power devices or running at high load for long periods of time while the vehicle is in operation may result in an circuit overload, causing the current to exceed its normal working range. The fuse monitors the current, and when the current exceeds the rated value for a certain period of time, the fuse melts, cutting off the circuit and preventing the electrical equipment from overheating. In a battery management system, for example, if the battery's output current remains too high, the fuse can promptly jump, protecting key components such as batteries and motors.
Fault Circuit Isolation: When a part of a high voltage circuit fails, the fuse's melting separates the faulty part from the rest of the normal part, preventing further escalation. For example, by installing different fuses in the charging and driving systems, if the charging system fails, only the charging system fuse melts, while the driving system continues to function, making it easy to quickly locate fault location and have maintenance personnel troubleshoot it.
III. Technical Characteristics and Selection Requirements: Rated Voltage and current: The rated voltage of the fuse must be greater than the maximum circuit voltage (including fault voltage) to ensure effective risk mitigation in overcurrent conditions. Electric vehicle high-voltage fuses, for example, are typically rated at 60VDC-1500VDC and need to be selected based on the actual peak voltage of the vehicle's high-voltage electrical platform. The rated current needs to be reassessed according to load characteristics to avoid premature fuse fatigue due to circulating current.
Damage capacity and response speed: HVDC arcs do not naturally cross zero, making them more difficult to extinguish; therefore, the fuse must be highly destructive. Fast fuses are suitable for short circuit protection and time delay fuses can withstand large overload currents in a short time.
DC Protection Characteristics: DC current systems of electric vehicles, such as lithium batteries, energy storage capacitors, electric motors, etc., mainly rely on DC fuses for short circuit protection. DC fuses must be designed with the L/R time constant (inductance to resistance ratio) in mind to ensure reliable fracture under specific circuit conditions.
