What is the function of actuating solenoids?
Actuating solenoids should shift a mechanically moveable part with a specified force along a specified path (stroke s).
Figure right: function of an actuating solenoid with spring load: s1 stroke start, s2 stroke end, FH holding force (magnetic), FF1 spring force at stroke start, FF2 spring force at stroke end, W1 static stroke work W2 dynamic stroke work
Spring forces If springs are used in actuating solenoids, they reduce or enhance the externally available mechanical forces.
Holding forces In the stroke start or stroke limit position, the armature of the solenoid is able to remain with holding force FH (see figure right). One of these positions is usually held by magnetic forces, while the other forces are held by a spring or other external forces, respectively. Depending on the magnet configuration, the magnetically held position is held via current flow from the coil or by permanent magnets.
Armature return movement
Prior to executing a new working stroke, the armature must be returned to the stroke start position. This is completed via built-in or external springs or from outside by the mechanical drive that the solenoid is used in. In case of reversible solenoids, the stroke start and stroke end position change with the active working direction.