Application Of Fuses in Electric Vehicles

A New Energy Fuse in an electric vehicle (EV) is an electrical device designed to protect circuits by interrupting the connection through the melting of its fusible element when the current exceeds a specified threshold. Widely used in high/low-voltage power distribution systems, control systems, and electrical equipment, fuses are one of the most prevalent protective components in EVs.

The circuit protection role of EV fuses involves safeguarding both wiring and electrical components. For wiring, fuses prevent overheating and potential fires, while for electrical devices, they provide overload protection to avoid damage. Consequently, when designing an EV's electrical system, careful consideration must be given to the power requirements of the equipment and the systematic compatibility among wires, fuses, and other components.

New Energy Electric Vehicle Fuse Standards primarily fall under three categories: IEC, UL, and ISO. Chinese GB, German DIN, and British BS standards largely align with IEC standards. Key standards include:
IEC: IEC 60127 (miniature fuses), IEC 60269 (low-voltage fuses).
UL: UL 248 (supplemental fuses).
ISO: ISO 8820 series (road vehicle fuses).
In China, there are currently 37 active or upcoming national standards (GB) for fuses, along with industry-specific standards tailored to voltage levels or applications. For automotive use, the GB 31465 series (referencing ISO 8820) is primarily adopted.

1. Rated Voltage:
The New Energy EV Fuses' rated voltage must exceed the nominal voltage of the electrical system to account for potential overvoltage scenarios. Under overvoltage conditions, an underspecified fuse may rupture or explode.

2. Rated Current and Continuous Operating Current:
Rated Current: Defines the fuse's maximum current capacity.
Continuous Operating Current: The maximum sustained current under the highest ambient temperature. This value must remain below the rated current to avoid long-term thermal degradation.

3. Connection Resistance:
High connection resistance increases temperature at contact points, reducing effective operating current. In practice, OEM-specified fuses, connectors, and sleeves must be tested under thermal equilibrium to ensure compliance with specified limits.

4. Ambient Temperature:
Bolt Connection Type Quick Fuse performance is temperature-dependent. Exceeding the operational temperature range increases internal resistance, leading to temperature rise and derating. Ambient temperature and derating coefficients must be factored into selection.

5. Time-Current Characteristics:
New Energy Vehicles Fuse operate based on current protection. They must interrupt the circuit before the wire reaches its maximum operating temperature (TmaxTmax) to prevent fire hazards.

6. Selectivity:
A layered fuse design ensures that lower-level fuses activate before higher-level ones, isolating faults without disrupting the broader electrical system.

7. Surge Resistance:
EV fuses must withstand inrush currents (e.g., from motor startups or capacitor charging) without unintended tripping. Slow-blow fuses or time-delay designs are often employed to differentiate between transient surges and fault current.

Beyond voltage and current, EV fuse selection must account for:

Environmental factors: Temperature, ventilation, altitude.

System interactions: Electromagnetic interference (EMI) between power electronics.

Validation: Testing under extreme conditions (e.g., rapid acceleration, fast charging).

A basic EV electrical system includes a fuse, connecting wires, and a load. The Electric Vehicle Fuse's core function is to protect wires from overheating by interrupting the circuit before thermal damage occurs. Therefore, wire selection and verification are integral to fuse selection. GB/T 31465.2 provides a standardized flowchart for this process, addressing factors such as: System-rated current, Peak current surges, Environmental conditions, Wire specifications.

While standards and manufacturers offer general guidelines, real-world development must also account for interactions within the electrical system. EVs, with their complex power electronics (e.g., inverters, DC-DC converters), may exhibit unique behaviors due to component interplay, necessitating rigorous testing and simulation.