CHAPTER 8 - ARC SUPPRESSION

INTRODUCTION OF ARC SUPPRESSION

     Arc suppression is the reduction of sparks formed when current-carrying contacts are separated. The spark is a luminous discharge of highly energized electrons and ions, and is an electric arc.

     There are several possible areas of use of arc suppression methods, among them metal film deposition and sputtering, arc flash protection, electrostatic processes where electrical arcs are not desired (such as powder painting, air purification, PVDF film poling) and contact current arc suppression. In industrial, military and consumer electronic design, the latter method generally applies to devices such as electromechanical power switches, relays and contactors. In this context, arc suppression is contact protection.

Arc suppression as contact protection

     Every time an electrical power device (for example: heaters, lamps, motors, transformers or similar power loads) turns on or off its switch, relay or contactor transitions either from a closed to an open state (break arc) or from an open to a closed state (make arc & bounce arc), under load, an electrical arc occurs between the two contact points (electrodes) of the electromechanical power switch, relay or contactor. The break arc is typically more energetic and thus more destructive.

     The energy contained in the resulting electrical arc is very high (tens of thousands of degrees Fahrenheit), causing the metal on the contact surfaces to melt, pool and migrate with the current. The extremely high temperature of the arc cracks the surrounding gas molecules creating ozone, carbon monoxide, and other compounds. The arc energy slowly destroys the contact metal, causing some material to escape into the air as fine particulate matter. This very activity causes the material in the contacts to degrade quickly, resulting in device failure.

     Arc suppression is an area of interest in engineering because of the destructive effects of the electrical arc to electromechanical power switches, relays and contactors’ points of contact.

Common devices

     Common devices used to prevent arcs are capacitors, snubbers, diodes, Zener diodes, varistors, transient voltage suppressors, and voltage-dependent resistors. Contact arc suppression solutions that are considered more effective:

• Two-wire contact arc suppressor 
• Solid state relays are not electromechanical, have no contacts, and, thus, do not create electrical arcs. 
• Hybrid power relays 
• Hybrid power contactors 

Benefits of Arc Suppression
     Arc suppression techniques can produce a number of benefits.

• Minimized contact damage from arcing and therefore reduced maintenance, repair and replacement frequency. 
• Increased Contact reliability. 
• Reduced heat generation resulting in less heat management measures such as venting and fans. 
• Reduced Ozone and pollutant emissions. 
• Reduced Electromagnetic Interference (EMI) from arcs - a common source of radiated EMI. 

References:

Petruzella, Frank. 1996. Industrial Electronics. Mc-Graw Hill. Singapore

http://royaleaves.com/blog/concept-electrical-arc/ 2 Mei 2014