The short circuit protection is a critical function of a device that connects the power source to the load. Its main purpose is to quickly disconnect the short-circuit point from the power source when a fault occurs on the load side, thereby preventing further damage and limiting the fault area.
Short-circuit breaking capability refers to the device's ability to safely interrupt the short-circuit current without being damaged itself. This ensures that the system remains stable and prevents the fault from escalating. A device with short-circuit protection must also have sufficient breaking capacity, and vice versa — they are closely related but not entirely the same.
For example, consider a typical air circuit breaker. If the short-circuit current exceeds its breaking capacity, the breaker may trip, but it might not be able to fully interrupt the current, leading to potential damage. This could happen due to improper selection of the breaker or limitations in the grid’s capacity. The actual short-circuit current depends on factors like power supply strength and line impedance, which must be considered during design.
It’s important to note that if an inverter is damaged after a short circuit, it doesn’t necessarily mean it lacked short-circuit protection. Instead, it could indicate a problem elsewhere in the system, such as incorrect configuration or component failure.
Breaking capacity is commonly used for high- and low-voltage circuit breakers and fuses, referring to their arc-quenching ability during a short circuit. In some older systems, like early AEG frequency converters, the control board was mounted on a metal plate, and the DC bus had a quick-melt fuse. Siemens inverters typically use output reactors, which help limit short-circuit currents. However, in certain cases — such as when a braking resistor causes a short circuit — the rectifier section can still be damaged, especially if the incoming line uses a standard circuit breaker.
If an inverter is damaged due to a short circuit, it often suggests that the protection response was too slow or inadequate. Modern inverters rarely use fast-melting fuses on the DC side, and it’s unclear whether output reactors effectively limit short-circuit currents.
On the output side, inverters generally don't include hardware-based short-circuit protection because the power devices used, such as IGBTs (Insulated Gate Bipolar Transistors), are designed to withstand short circuits. When a short occurs, the IGBT locks out and stops current flow, protecting itself from damage. Adding external protection could actually be counterproductive, as the short-circuit current rises too quickly for any external device to react in time.
Moreover, IGBTs are not designed to handle open-circuit conditions. If the load suddenly opens during operation, the rapid voltage change (dv/dt) can cause the IGBT to fail, even if there's no actual short circuit. This is similar to how a river dam closing suddenly creates a surge that impacts the upstream — in this case, the IGBT.
Overload and short-circuit conditions are different. Short-circuit current is much higher than overload current, and IGBTs can respond quickly by shutting down. However, prolonged overload can lead to thermal stress and eventual failure. That’s why modern inverters include both short-circuit and overload protection mechanisms.
Inverters using diodes or thyristors on the input side lack self-protection and require external short-circuit protection. But if the input stage uses IGBTs (such as in ALM configurations), the input can also have built-in short-circuit protection.
The development of IGBTs focused heavily on improving their ability to resist short circuits. Since external switches or fuses couldn’t provide enough protection, IGBTs were designed with internal current cutoff features. This allows them to lock out immediately upon detecting a short, preventing damage and ensuring safe operation.
In summary, IGBTs are inherently resistant to short circuits, and their design makes them more reliable than older technologies like thyristors. However, other factors — such as sudden load disconnection or excessive overload — can still cause failures. Understanding these nuances helps in designing more robust and reliable power systems.
Vision SE is our specialist vision solution offering a wide range of classification services. Through advanced image processing, we realize professional-level visual technology, which is suitable for medical image processing, scientific research and other fields. We focus on performance optimization to make it an industrial-grade solution that is widely used in factory automation and high-demand application scenarios. At the same time, we pay attention to data security and privacy protection, ensuring that the highest standards are met when processing images and data. Vision SE's classified services exceed expectations, providing high-performance and professional-grade vision solutions to various industries.
vision services,vision sensor,vision sense,vision se,vision se review
Ningbo Autrends International Trade Co., Ltd. , http://www.visionsemr.com