Transcript:
[0m:00s] Hey, I’m Mitchell and welcome to another video in the RSP education series. Think of a relay like a bridge between low voltage control systems and high power machinery. Without proper maintenance and safeguards, that bridge can collapse and take your entire system down with it. Today we’re covering arc suppression, flyback diodes, and overload protection. One tiny spark can lead to catastrophic failure. Relays are a constant in industrial systems, but without protection they can become ticking time bombs. We’ll discuss how engineers prevent arcing fires, back EMF surges, and short circuits. If you like this content and want more educational videos, like and subscribe. This video is for educational purposes only. Consult a professional for your application. RSP Supply is not liable for any misuse of this information. Let’s jump right in.
[1m:20s] Let’s start with arc suppression. When a relay opens or closes under high current, an electric arc can form between the contacts. This arc generates extreme heat, damages the contacts, and shortens relay lifespan. One way to suppress arcing is with snubber circuits or RC circuits, which use a resistor capacitor network to absorb voltage spikes. Another option is spark arrestors or varistors, also called MOVs, which divert high voltage surges away from the contacts. Some relays also use inert gases like nitrogen to extinguish arcs faster.
[2m:03s] Another critical component is the flyback diode. When a relay coil is deenergized, the collapsing magnetic field generates a high voltage spike called back EMF. This spike can damage sensitive electronics like PLCs or microcontrollers. A flyback diode, also called a freewheeling diode, is placed in reverse bias across the coil to provide a safe path for current when the coil turns off. Without it, voltage spikes can reach hundreds of volts and travel back into control devices.
[2m:53s] Fuses and overload protection are also essential. Relays can fail due to excessive current from short circuits or overloads. Fuses are one time use devices that burn out when current exceeds their rating. Fast acting fuses protect against sudden surges, while slow blow fuses handle temporary overloads. Overload relays can be thermal or magnetic. Thermal overloads use a bimetallic strip that bends when overheated to cut power, while magnetic overloads trip instantly when current exceeds a set limit.
[3m:32s] Relays do not fail on their own, they fail due to lack of protection. Snubber circuits tame arcing, flyback diodes clamp voltage spikes, and fuses stop catastrophic overloads. When properly protected, relays last longer and protect everything downstream. For a full line of relays and hundreds of thousands of industrial automation products, visit rspsupply.com, the internet’s best source for industrial automation hardware.