Page 134 - Electromechanical Devices and Components Illustrated Sourcebook

96 Electromechanical Devices & Components Illustrated Sourcebook

Solenoids Coil Asymmetric
Field Lines
Coil Form
Solenoids represent an extremely important use of magnetics
in the mechanical world. They are used in literally millions of
different applications throughout the world.
Moving
When a current is applied to a coil, a magnetic field is pro-
Iron Core
duced in air, as shown in Figure 5-46. The field lines are sim-
ilar to a bar magnet, except they are in the shape of a toroid. Pull
In the absence of any outside influences the field is balanced.
When an iron core is placed into the coil, an electromagnet
is formed and the field lines are coupled to the core. If the
core is not centered in the coil, as shown in Figure 5-47, an
asymmetric load is generated. The asymmetric load tries to
force the core into the center of the coil and balance the mag-
netic field. In this way usable mechanical force can be gener-
+ −
ated at the push of a button.
Figure 5-48 shows a paddle-style solenoid. The “L”-frame
core and paddle represent the magnetic circuit. When the coil
is energized, the paddle is pulled onto the core with consider-
Push Button
able force. “C”-frame solenoids provide more travel than a
paddle type. The magnetic circuit is in the form of a C-shaped Battery
frame with the coil mounted in the center. A guide rod and
keeper made from iron complete the circuit. Figure 5-49
shows a “C”-frame style solenoid. These types of solenoids
are generally inexpensive and can be found in all manner of
equipment.
Laminated-core AC solenoids are generally used for high-
load applications. They are similar in geometry to “C”-frame Figure 5-47 Solenoid
units, except that they use a riveted laminated core and the
Return Spring

Coil
"L" Frame
Pivot Pin
Field Lines
Coil
Paddle

Terminals

Throw
Figure 5-48 Paddle-Style Solenoid
+ −
Core w/Through
Hole
Keeper "C" Frame
Push Button
Guide Rod
Battery Coil
Bolt Lug Extension Stop
Terminals

Throw
Figure 5-46 Solenoid Coil Figure 5-49 C-frame Style Solenoid