Arc voltage drop is a phenomenon that occurs in rectifiers and converters when an arc or a high-current electrical discharge is established between two electrodes or contacts. This voltage drop is primarily a result of the resistance and inductance of the arc itself, which causes a reduction in the voltage across the electrodes compared to the applied voltage.
In rectifiers and converters, such as in power electronic systems, switching devices like diodes, thyristors, and transistors are used to control the flow of current. During the switching process, there can be instances where the current is interrupted abruptly, leading to the formation of an arc between the switching elements or contacts. This arc can create a temporary short circuit path for the current, which is typically undesirable and can result in several issues:
Voltage Drop: The arc that forms between the electrodes has a certain resistance due to the ionization of the surrounding air or medium. This resistance leads to a voltage drop across the arc. This voltage drop can reduce the effective voltage across the load or the switching element, impacting the system's performance and efficiency.
Energy Loss: Arc voltage drop represents energy that is dissipated as heat within the arc itself. This energy loss can contribute to inefficiencies and increase the operating temperature of the components involved, potentially affecting their lifespan.
Electromagnetic Interference (EMI): Rapid switching and the creation of arcs can generate electromagnetic interference, which might affect other nearby electronic systems or devices, causing signal distortion or malfunction.
Component Stress: The repeated formation and extinguishing of arcs can subject the switching devices to thermal and mechanical stress, potentially leading to premature failure of these components.
To mitigate arc voltage drop and its associated issues, engineers implement various techniques and strategies, such as:
Snubber Circuits: Snubber circuits are designed to absorb the energy stored in the arc, reducing the voltage spike across the switching element when the arc is extinguished.
Use of Snubber Components: Capacitors and resistors can be used in parallel with switching elements to help suppress arc voltage drop and limit its negative effects.
Proper Switching Techniques: Implementing controlled and gradual switching techniques can minimize the chances of sudden current interruptions and arc formation.
Improved Contact Design: In industrial and high-power applications, using specialized contact materials and designs that can handle high current and reduce arcing can help mitigate arc voltage drop.
Arc Quenching Techniques: Some applications require arc quenching methods, such as using magnetic fields, dielectric mediums, or cooling techniques to rapidly extinguish arcs and prevent their reformation.
By carefully designing the switching circuits, considering the properties of the switching elements, and implementing appropriate control strategies, engineers aim to minimize arc voltage drop and its associated problems, thereby improving the overall efficiency, reliability, and safety of rectifiers and converters.