**1. Introduction**

Clean renewable energies have laid a platform for practical DC distribution systems in applications such as commercial buildings, data centers, microgrids, and shipboard power systems [1–5]. Solid-state circuit breakers (SSCBs) have been deemed the most ideal form of protection in developing DC systems due to inadequacies in standard AC protection methods. AC breakers work in connection with the zero crossing of the alternating voltage and current to mechanically extinguish a fault through arcing. Arcing in DC systems is indefinitely sustained unless larger airgaps are used for the same AC rating. Attempts have been made to reduce an AC breaker's voltage and current ratings by as much as half for use in DC systems, but their overall effectiveness remains scrutinized due to the speed at which they operate [6–10]. DC microgrids rely on power electronic converters to operate and are often unable to sustain prolonged faults, making it necessary to reduce instantaneous trip ratings. The fastest SSCBs have reported clearing times of just a few microseconds, where the mechanical AC breaker operates in tens of milliseconds. The comparison of an SSCB and thermomagnetic circuit breaker can be found in Figure 1 [11].

**Figure 1.** Trip curve comparison of an solid-state circuit breaker (SSCB) and thermomagnetic circuit breaker [11].

Several methods of SSCB design have been researched using different types of semiconductor devices for various applications. Silicon insolated-gate bipolar transistor (IGBT) devices are the most commonly reported [12–14]. More expensive wide-bandgap semiconductors with higher voltage ratings and lower losses have also been investigated [15–17]. Figure 2 depicts the basic structure of a DC distribution system, illustrating a general protection scheme. The SSCB is built to operate in a unidirectional or bidirectional mode, depending on its placement in the distribution system due to multiple generation sources. The placement of the devices determines the system voltage level, which can range from 28 V for low-level systems, such as lighting, to 1 kV for general distributions [18].

**Figure 2.** Generalized block diagram for a DC microgrid protection scheme with multiple generation sources [18].

At least two commercial SSCBs have been designed for use in a conventional three-phase AC distribution system, but, currently, the AC breaker remains the most widely used protection device in experimental DC systems. The development of new SSCB technology shows promise for the future of integrated power systems, but the cost associated with new technologies remains a hindrance in the growth of commercial DC systems. Continued research into affordable and reliable protection schemes is essential to the development of efficient clean energy systems. Expanding interests in the DC protection market provide a unique opportunity for the research and growth of future DC distribution systems. In this context, this article investigates the viability of a low voltage SSCB using commercially available low-cost off-the-shelf components.

The SSCB proposed in this article was used to provide the building blocks necessary to anyone interested in the subject, provide insight into possible improvements in the design, and further the research into effective low-cost solutions of SSCB implementation while highlighting the most troublesome areas of the design process, such as switching, thermal requirements, and speed.

The following section details the design process for a unidirectional low voltage SSCB using a silicon IGBT. The SSCB was designed for the low-end protection of lighting and/or other sensitive low current electronics. The device was tested in a laboratory setting, and the results were used to verify the SSCB voltage and current ratings. All external experiments were conducted using randomly generated test conditions to minimize error and improve the output reliability. The materials used in the creation of the device were purchased through an electronics vendor, and information and data sheets are available online.
