Solenoid
From Free net encyclopedia
A solenoid is a loop of wire, often wrapped around a metallic core, which produces a magnetic field when an electrical current is passed through it. Solenoids are important because they can create controlled magnetic fields and can be used as electromagnets.
In physics, the term solenoid refers specifically to a magnet designed to produce a uniform magnetic field in a volume of space (where some experiment might be carried out).
In engineering, the term solenoid may also refer to a variety of transducer devices that convert energy into linear momentum. The term is also often used to refer to a solenoid valve, which is an integrated device containing an electromechanical solenoid which actuates either a pneumatic or hydraulic valve, or a solenoid switch, which is a specific type of relay that internally uses an electromechanical solenoid to operate an electrical switch; for example, an automobile starter solenoid, or a linear solenoid, which is an electromechanical solenoid.
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Electromechanical solenoids
Electromechanical solenoids consist of an electromagnetically inductive coil wound around a movable steel or iron slug (termed the armature). The coil is shaped such that the armature can be moved in and out of the center, altering the coil's inductance and thereby becoming an electromagnet. The force applied to the armature is proportional to the change in inductance of the coil with respect to the change in position of the armature, and the current flowing through the coil. The force applied to the armature will always move the armature in a direction that increases the coil's inductance.
Pneumatic solenoids
A pneumatic solenoid valve is a switch for routing air to any pneumatic device, usually an actuator of some kind. A solenoid consists of a balanced or easily moveable core, which channels the gas to the appropriate port, coupled to a small linear solenoid. The valve allows a small current applied to the solenoid to switch a large amount of high pressure gas, typically at around 100 psi (7 bar, 0.7 MPa, 0.7 MN/m²).
Pneumatic solenoids may have one, two, or three output ports, and the requisite number of vents. The valves are commonly used to control a piston or other linear actuator.
The pneumatic solenoid is akin to a transistor, allowing a relatively small signal to control a large device. It is also the interface between electronic controllers and pneumatic systems.
Hydraulic solenoids
Hydraulic solenoid valves are in general similar to pneumatic solenoid valves except that they control the flow of hydraulic fluid (oil), often at around 3000 psi (210 bar, 21 MPa, 21 MN/m²). Hydraulic machinery uses solenoids to control the flow of oil to rams or actuators to (for instance) bend sheets of titanium in aerospace manufacturing.
The basics of solenoid valves
Solenoid valves are the most frequently used control elements in fluidics. Their tasks are to shut off, release, dose, distribute or mix gases and fluids. They are found in many application areas, for example: Fast and safe switching, high reliability, long service life, good medium compatibility of the materials used, low control power and compact design.
Besides the plunger-type actuator which is used most frequently, pivoted-armature actuators and rocker actuators are also used.
External links
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