30-01-2024, 11:30 AM
AC through a simple solenoid coil is bad news - the current drops to zero twice each cycle, and so does the holding force. So the armature buzzes and chatters. Try it!
So, an AC relay coil has a 'D' shaped piece of copper surrounding part of the pole-piece. Eddy currents in this delay the passing through zero of the field in this part of the pole-piece. It means that somewhere on the pole-piece, there's always some field, so always some holding force.
So, an AC relay coil has a 'D' shaped piece of copper surrounding part of the pole-piece. Eddy currents in this delay the passing through zero of the field in this part of the pole-piece. It means that somewhere on the pole-piece, there's always some field, so always some holding force.
