A mechanical circuit breaker physically pulls contacts apart to clear a fault, taking milliseconds and producing an arc. In DC systems — microgrids, ships, data centres, EVs — there is no natural current zero to extinguish that arc, making interruption hard. Solid-state circuit breakers (SSCBs) replace moving contacts with power semiconductors that switch off in microseconds, without arcing.
Working principle
Current normally flows through a low-resistance semiconductor switch (a SiC MOSFET or IGBT). A fast detection circuit senses an overcurrent and commands the device to turn off in microseconds. Because the interruption is so fast, the fault current never reaches its peak, limiting damage. A snubber and surge arrester absorb the energy stored in line inductance during the abrupt cut-off.
| Property | Mechanical | Solid-state |
|---|---|---|
| Interruption time | Milliseconds | Microseconds |
| Arcing | Yes | None |
| On-state loss | Negligible | Conduction loss |
| DC capability | Difficult | Native |
| Lifetime / wear | Contact wear | No moving parts |
Key trade-offThe penalty is continuous conduction loss in the semiconductor; hybrid breakers combine a mechanical path for low steady-state loss with a solid-state path for fast interruption.
Applications
- DC microgrids, shipboard and aircraft power systems
- EV and battery-pack protection
- Data-centre DC distribution and HVDC grids
References & further reading
- Meyer et al., “Solid-State Circuit Breakers and Current Limiters for Medium-Voltage Systems,” IEEE Trans. Power Electronics, 2004.
- Rodrigues et al., “A Review of Solid-State Circuit Breakers,” IEEE Trans. Power Electronics, 2021.
- Shen et al., “Ultrafast Solid-State Circuit Breakers using SiC,” IEEE JESTPE, 2019.