OL Contactor

OL Contactors are typically used between a motor starter and a Motor, in line, and typically use Bi-Metal Overload contacts which when the current rises to it's rating causes the metal to liquify, releasing a contact stud that rotates releasing a claw that when in a low current condition contacts the non- rotating contact stud providing the current path, when liquified the contact stud rotates, the claw no longer provides contact to the stud and there is no longer a path for the current. When the Metal cools, the stud will no longer rotate and the claw position can be reset by pressing the reset button pushing the claw into a constant contact position on the stud.

There are Solid State OL devices, that use electronic power devices to pass the current while monitoring the current level, when the current limit trip point is reached (which is typically selectable within a certain operating range) the device is turned off and an LED and or switch indicates the OL has tripped. The unit can then be reset as long as the reason for the higher current loading has been corrected. (Typically a process malfunction, Jam, etc., or the current issue could be caused by some type of Motor failure.) Another source with more technical information then I can provide here is WIKIPEDIA.org, just type in your point of interest and you will be provided with much good and typically reliable information.