Contactor Design:
Pin and Sleeve vs Meltric¨ Silver Nickel Butt Contacts

All electrical accessories are designed to ensure the largest possible contact surface.  Some industrial plugs and receptacles have brass cylindrical pins and conical contact tubes. 

Electrical contact is made at right angles to its insertion and withdrawal.  Contact between cylindrical and conical surfaces is made on points of a circle.  The force applied to these points, which varies from one pin and sleeve to another, is generated by a cylindrical spring or laminate to deform the area around or in the sleeve. 

The sleeve or laminate eventually reach a permanent deformed state, which translates into lower contact pressure and higher contact resistance (a build up of heat).  This heating accelerates the oxidation rate and eventually leads to contact failure.  Silver plated contacts increase the connector life (until the silver is worn away by the insertion process). 

To make sure your connections are reliable, Meltric¨ plugs and receptacles use silver nickel pressure type contacts, similar to those found in motor starters. 

The contacts are spring loaded at a controlled applied force.  The force applied to the contacts is on the same plane as the insertion and extraction movements, so a limited force is needed to insert a plug into its receptacle and no force is necessary to withdraw it. 

When the plug and receptacles pressure contacts first touch, their faces are parallel, as the plug engages, the two faces slide against each other, align, and then perform a wiping action. 

Receptacle channeling causes the plug to twist slightly.  Further wiping occurs as contact pressure increases, the result is a reliable electrical connection. 

When clean, the resistance of silver-nickel is very low and varies only slightly with time and oxidation.  Silver sulfide is also a good conductor.

Connectors at a Glance