Electromagnetic Devices ECE 201 Circuit Theory I
Solenoid Has a movable iron core called a plunger ECE 201 Circuit Theory I
ECE 201 Circuit Theory I
Unenergized state Plunger is extended ECE 201 Circuit Theory I
Plunger is extended by the force of the spring ECE 201 Circuit Theory I
Energized State Plunger is retracted ECE 201 Circuit Theory I
Both iron cores become magnetized, and the South pole of the stationary core attracts the North pole of the movable core, causing it to slide inward, retracting the plunger and compressing the spring. This happens as long as there is sufficient current. When the current is turned off, the magnetic fields collapse and the force of the spring pushes the plunger out. ECE 201 Circuit Theory I
Uses of Solenoids Provide movement Door locks Valves ECE 201 Circuit Theory I
Relays Used to open or close contacts (switches) Mechanical Relay ECE 201 Circuit Theory I
ECE 201 Circuit Theory I
Terminal Identifications 1 – Common (COM) 2 – Normally Closed (NC) 3 – Normally Open (NO) 4 and 5 – Coil This is a single – pole double – throw relay ECE 201 Circuit Theory I
Unenergized State Normally Closed Armature is held against the upper contact by the force of the spring Continuity between terminals 1 and 2 ECE 201 Circuit Theory I
Energized State Normally Closed contact is opened, Normally Open contact is closed. ECE 201 Circuit Theory I
ECE 201 Circuit Theory I
Energized State Armature is pulled down by the electromagnetic field Continuity between terminals 1 and 3 ECE 201 Circuit Theory I
Typical Construction and Circuit Symbol ECE 201 Circuit Theory I
Loudspeaker Interaction between the fields of a coil and a permanent magnet ECE 201 Circuit Theory I
South pole of permanent magnet is positioned within the coil ECE 201 Circuit Theory I
Magnetic field produced by the current interacts with the permanent magnet field, causing the coil to move right ECE 201 Circuit Theory I
When the current in the coil reverses, its field is in the opposite direction, causing the coil to move left. ECE 201 Circuit Theory I
For a time – Varying Signal ECE 201 Circuit Theory I
Coil motion in both directions Time – Varying signal (voltage or current) ECE 201 Circuit Theory I