Transient current spikes often cause faster relay contact degradation than regular switching operations — outpacing degradation from standard on. When a relay closes or opens a circuit, especially under inductive or capacitive loads, a brief but intense surge of current can flow through the contacts. The peak current far surpasses the relay’s nominal load capacity, triggering micro-welding, plasma discharge, and contact wear.
Over time, repeated exposure to these surges leads to pitting and welding of the contact material. Pitting occurs when small amounts of metal are vaporized during arcing, producing uneven, eroded contact regions. Surge energy can fuse contacts into a solid metallic bond, preventing reliable circuit interruption. Both conditions degrade the relay's ability to make clean, low-resistance connections.
Surge currents are particularly common in applications involving motors, transformers, and lighting systems with high inrush currents. Even if the relay is correctly rated for the steady state load, it can still degrade rapidly without surge-rated construction.
For reliable operation, specify relays engineered for surge endurance, typically labeled with elevated switching capacity metrics. Using snubber circuits, varistors, انواع رله or RC networks can also help suppress surges. by dissipating destructive energy through auxiliary circuitry. Selecting contacts made from arc-resistant composites like silver-nickel or silver-tin oxide, providing enhanced durability under high-current transients, can improve durability.
Routine inspection and diagnostic testing reveal incipient contact wear. such as increased contact resistance or delayed switching. By proactively addressing transient current threats, design teams can eliminate premature relay breakdowns, and ensure longer, more reliable operation of relay-based circuits.
