Electric devices intended to use for holding of ferromagnetic objects. It is possible to use them also as lifting electromagnets with small stroke but high pulling force. Holding solenoid with permanent magnet has inverse function (generates holding force when current is switched off, releases the load when current is switched on). When the solenoid is activated, magnetic flux flows through the active area between north and south magnetic pole. In this phase magnetic circuit is open. When ferromagnetic yoke is attached to the active area, magnetic circuit closes and the solenoid generates much higher holding force.
Holding force of these electromagnets is negatively influenced by the following factors:
- foreign materials in the body and yoke of the electromagnet (carbon, chrome, nickel, manganese, etc.)
- roughness of contact faces (the higher roughness the lower holding force)
- air gap (the bigger air gap the lower holding force)