How exactly does a plunger relay work?

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A plunger relay operates by using a coil that generates a magnetic field, causing the armature to move and close contacts in another circuit. The discussion raises a question about how AC, which produces a sinusoidal magnetic field, can effectively move the plunger instead of causing it to vibrate. It suggests that the armature's design, possibly using materials like aluminum, may allow for consistent movement due to magnetic repulsion from the changing magnetic field. The magnetic flux acts on the larger end of the plunger shaft, facilitating its extension. Understanding these mechanics clarifies how AC can effectively operate a plunger relay.
elegysix
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Hi, I'm new to relays.
As I understand it, there is a coil which creates a magnetic field to cause the armature to move (such as a plunger) and closes the contacts of another circuit. My question is this - how can the AC cause the plunger to move? isn't the AC producing sinusoidal B field, which would cause the plunger to vibrate, not extend?
Or is the armature made of say aluminum where the changing B field always causes repulsion?

thanks
 
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The magnetic flux is not acting on the shaft of the plunger, but on the larger end at the end of the shaft.
 

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