Megawatt EV charging requires high-voltage, high-current power distribution combined with fast and reliable protection. As charging power increases, components such as contactors, circuit breakers, current sensors and busbars must work together to safely control and interrupt high-energy DC circuits. A PyroFuse adds an additional layer of safety by rapidly interrupting severe fault currents, helping to protect the battery, power electronics and users from potentially dangerous electrical faults.
PyroFuse: Fast, Reliable EV Circuit Protection
A PyroFuse is a pyrotechnic circuit breaker designed to rapidly interrupt high-voltage, high-current circuits in electric vehicles. When triggered by a low-voltage signal from the vehicle’s control system, a pyrotechnic initiator generates gas pressure that drives a plunger through the busbar, physically breaking the circuit. The resulting electrical arc is then rapidly suppressed inside the sealed chamber. PyroFuses are used when conventional contactors cannot safely interrupt a fault current, such as during a battery short circuit, severe overcurrent or a crash, typically within just 2–5 ms.
The role of the contactor
The contactor provides controlled switching and galvanic isolation of the high-voltage circuit. In high-power charging systems, bidirectional operation is particularly important because energy can flow both into and out of the battery. The GXVB611 1000VDC/600A Bi-Directional Contactor from Sensata is designed for applications such as DC fast charging, energy storage systems and battery-electric special mobility. Its gas-filled, hermetic design provides low electrical resistance, efficient arc cooling and high fault-interrupt capability. The IP67 construction also supports demanding operating environments.
The GXVB611 can handle up to 600 A at 1000 VDC, corresponding to approximately 600 kW of electrical power. It therefore fits well within modular MW-class charging architectures.
Its dual DC coils are designed for very low continuous 24 VDC power consumption, with no EMI emissions or cross-talk on the control power supply. Built-in coil suppression further reduces external components and engineering effort.
Fast Fault Protection
A contactor alone cannot safely interrupt every high-energy short circuit. A dedicated fast circuit protection device can be connected in series with the contactor to interrupt fault currents before they cause severe damage.
The Sensata PyroFuse STPS500, for example, is a bidirectional pyrotechnic circuit breaker rated for up to 500 A continuous current and capable of interrupting very high fault currents at up to 1000 V. Its response time is below 1 ms in the specified configuration.
This combination of contactor + fast circuit protection provides controlled switching during normal operation while offering rapid isolation during severe fault conditions.
Designing for Megawatt Power
At MW charging levels, every part of the power path must be designed for high current, thermal load and fault energy. Short-circuit current can rise extremely quickly, while system inductance influences both the peak current and the energy that must be managed during interruption.
A safe architecture therefore combines:
- High-current, bidirectional contactors
- Fast fault-current interruption
- Current sensing and protection logic
- Proper busbar and cable design
- Thermal management
- Reliable galvanic isolation
For MW-class EV charging, safety is not provided by a single component. It comes from the coordinated design of the complete high-voltage power distribution system.
More information about this topic can be found here:
Sensata EL – Pyrofuse – Datasheet
Sensata EL – Pyrofuse – Whitepaper Maximizing circuit protection for enhanced EV Safety
Sensata GXCB611 Datasheet
If you want more information or if you have any questions, please contact Nijkerk Electronics!