## 3 DC Circuit Breakers
### Solid-State Circuit Breakers
#### 3.3.2 Recent Developments of SSCBs  
The following paragraphs show the most recent developments of SSCBs in terms of the type of semiconductors and material used:  
In the Ref. [75], the authors compared the switching waveforms of Si GTO and SiC GTO switches. The latter is known as an automatic turn-off device that controls high voltages and large currents. GTO is preferred for DC applications because it has an independent gate for turn-on and turn-off. The results showed Sic GTO times of 2.21 us, which are lower than Si GTO times of 10.82 us. In the Ref. [76], a SSCB based on IGBTs was implemented in a DCMG. The designed SSCB was capable of low-end lighting protection applications and tested at 50 V. A 15 A continuous current rating was obtained, and the minimum response time of the SSCB was nearly 290 times faster than that of conventional AC protection methods. The development of this technology shows promise for the future of integrated power systems; nonetheless, the cost associated with these new technologies remains an obstacle in the growth of commercial DC systems. In the Ref. [61], a new SSCB was designed based on IGCT technology for an aircraft DCMG. The authors proposed a new IGCT-based SSCB that uses Y-shape coupled inductors that forces the current to zero to isolate short-circuit faults. With this implementation, there is no need to add a snubber or clamp circuit across the IGCT because the Y-shape coupled inductors drive inductive currents to zero before the IGCT commutates off. They obtained a SSCB with an efficiency of 99.94%, and operating time of around 20 us. In the Ref. [10], a suitable IGBT for low-voltage (around 400 V) fault protection of a DCMG was proposed. The simulation results showed that the SSCB acted reliably and the fault current dropped to zero within 15 us until the fault was removed from the system and reconnected within 8 us, while the rest of the system continued to operate normally. However, the high conduction loss and cost of the semiconductor breakers technology was considered as the main obstacle to their wider use in electrical protection applications. Si IGBT-based breakers have also been proposed to interrupt fault currents In the Ref. [10]. However, these breakers feature relatively high power losses due to the finite conductivity modulation effect of the IGBT [77]. Besides, the maximum current interruption ability of these breakers are also limited by the saturation current of the IGBT which reduces the short-circuit requirements from 10 to 5 us. However, Si IGBT would reduce the on-state losses to increase the channel width-to-length ratio [78]. In the Ref. [22], Si MOSFET, Si CoolMOS, SiC MOSFET, and SiC JFET with the lowest on-resistance Rds (on) for a rated breakdown voltage devices were studied. The SiC junction-gate field effect transistor (JFET) has the best maximum turn-off capability, the maximum current that a switch can interrupt, and the highest peak power density. In the Ref. [68], a photovoltaic-driven SSCB with latching and current-limiting (LCL) capabilities (SSCB-LCL) was proposed. In case the load current is exceeded, the SSCB-LCL limits the load current during a pre-configured time by the user. If the fault persists, after the pre-configured time has elapsed, the load is disconnected from the input. External commands were also included for controlled load disconnection or restarting the SSCB-LCL. This circuit contains very few components, does not require external supply, and provides a large bandwidth control signal. Figure 6: Galvanic isolation circuit for SSCBs [73]. In the Ref. [17], the authors proposed a SSCB that detects short-circuit faults by sensing the drain source voltage, in which case it extracts power from the fault condition to turn off and stop a SiC JFET. The authors proposed a new two-terminal for the SSCB that can be placed directly on a circuit branch without requiring any external power supply or additional wiring. In the Ref.