Version 1.0, August 31, 2001, Copyright, Hugh Jack 1993-2001
· Contactor - special relays for switching of large loads.
· Motor Starter - Basically a contactor in series with an overload relay to cut off when too much current is drawn.
· Rated Voltage - suggested operation voltage. Lower levels can result in failure to operate, voltages above shorten life.
· Rated Current - The maximum current before contact damage occurs (welding or melting).
· DC relays require special arc suppression. AC relays have a zero crossing to reduce relay arc problems.
· AC relays require a shading pole to maintain contact. If a DC relay is used with AC power on the coil it clicks on-and-off at the frequency of the AC (also known as chattering).