Nowadays, the performance advantages brought by silicon carbide (SiC) devices in electric vehicle (EV) and solar photovoltaic (PV) applications have been widely recognized. However, the material advantages of SiC may also be applied in other applications, including the field of circuit protection. This article will review the development of this field and compare the advantages and disadvantages of mechanical protection and solid-state circuit breakers (SSCBs) implemented using different semiconductor devices. Finally, this article will also discuss why SiC solid-state circuit breakers are increasingly favored by people.

Protecting power infrastructure and equipment

The power transmission and distribution system as well as sensitive equipment need to be properly protected to prevent damage due to long-term overload and transient short circuit conditions. As the voltage used in the power system and electric vehicles increases, the possible maximum fault current is also higher than ever before. To provide protection against these high current faults, we need ultra fast AC and DC circuit breakers. In the past, mechanical circuit breakers have always been the main choice for such applications, but with increasingly stringent work requirements, solid-state circuit breakers are becoming more and more popular. Compared to mechanical circuit breakers, solid-state circuit breakers have many advantages:

·Robustness and reliability: Mechanical circuit breakers contain moving parts, making them relatively susceptible to damage. This means that they are prone to damage or accidental automatic disconnection due to movement, and wear occurs every time they are reset during use. In contrast, solid-state circuit breakers do not contain moving parts, making them more robust and reliable, and less prone to accidental damage. Therefore, they can be repeatedly opened/closed thousands of times.

·Temperature flexibility: The working temperature of mechanical circuit breakers depends on their manufacturing materials, so there are certain limitations in terms of working temperature. In contrast, solid-state circuit breakers have higher operating temperatures and can be adjusted, making them more flexible in adapting to different working environments.

·Remote configuration: Mechanical circuit breakers require manual reset after tripping, which can be time-consuming and costly, especially when deployed on a large scale at multiple installation points, and there may also be safety hazards. Solid state circuit breakers can be remotely reset through wired or wireless connections.

·Switching speed is faster and does not generate arcs: Mechanical circuit breakers may generate significant arcs and voltage fluctuations during switching, which can damage load equipment. Solid state circuit breakers adopt a soft start method, which can protect the circuit from the influence of these induced voltage spikes and capacitor surge currents, and the switching speed is much faster. In the event of a fault, it only takes a few milliseconds to cut off the circuit.

·Flexible current rating: Solid state circuit breakers have programmable current ratings, while mechanical circuit breakers have fixed current ratings.

·Smaller size and lighter weight: Compared to mechanical circuit breakers, solid-state circuit breakers are lighter in weight and smaller in volume.

Limitations of existing solid-state circuit breakers

Although solid-state circuit breakers have multiple advantages over mechanical circuit breakers, they also have some drawbacks, including limited voltage/current ratings, higher conduction losses, and higher prices. Typically, for AC applications, solid-state circuit breakers are based on thyristor rectifiers (TRIAC), while for DC systems, they are based on standard planar MOSFETs. TRIAC or MOSFET is responsible for implementing switching functions, while optical isolation drivers are used as control components. However, in the case of high output current, MOSFET based high current solid-state circuit breakers require the use of heat sinks, which means they cannot achieve the same power density level as mechanical circuit breakers.

Similarly, solid-state circuit breakers implemented using insulated gate bipolar transistors (IGBTs) also require heat sinks, as saturation voltage can lead to excessive power loss when the current exceeds tens of amperes. For example, when the current is 500 amperes, the 2V voltage drop on the IGBT will generate a power loss of up to 1000W. For the same power level, MOSFETs need to have about 4 meters? The conducting resistance of. With the voltage rating of devices in electric vehicles moving towards 800V (or even higher), there is currently no single device that can achieve this resistance level. Although theoretically multiple devices can be connected in parallel to achieve this number, this approach significantly increases the size and cost of the solution, especially when dealing with bidirectional currents.

Creating the Next Generation Solid State Circuit Breakers Using SiC Power Modules

Compared with silicon chips, SiC chips can shrink in size by up to ten times under the same rated voltage and conduction resistance conditions. In addition, compared to silicon devices, SiC devices have a switching speed at least 100 times faster and can operate at peak temperatures of up to twice or more. Meanwhile, SiC has excellent thermal conductivity, thus exhibiting better robustness at high current levels. Ansemy has developed a series of EliteSiC power modules using these characteristics of SiC, with a conduction resistance as low as 1.7m? In its 1200V device?. These modules integrate two to six SiC MOSFETs in a single package.

Sintered chip technology (sintering two independent chips into one package) can provide reliable product performance even at high power levels. Due to its fast switching behavior and high thermal conductivity, this type of device can quickly and safely "trip" (disconnect the circuit) in the event of a fault, preventing current flow until normal operating conditions are restored. Such modules demonstrate an increasing possibility of integrating multiple SiC MOSFET devices into a single package to achieve low on resistance and small size, thus meeting the needs of practical circuit breaker applications. In addition, Ansemy also offers EliteSiC MOSFETs and power modules with a voltage range of 650V to 1700V, so these devices can also be used to create solid-state circuit breakers suitable for single-phase and three-phase household, commercial, and industrial applications. Ansemy has a vertically integrated SiC supply chain that can provide products with almost zero defects. These products have undergone comprehensive reliability testing and can meet the needs of solid-state circuit breaker manufacturers.

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This is reported by Top Components, a leading supplier of electronic components in the semiconductor industry. They are committed to providing customers around the world with the most necessary, outdated, licensed, and hard-to-find parts.

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