Continuous Duty Linear Solenoids

Continuous duty linear solenoids convert electrical energy into mechanical power via a plunger with an axial stroke in either a push or pull action. They are rated for a 100% duty cycle and generally remain in an on-state without interruption for periods of approximately 30 minutes or longer. Electrical current is supplied to a coil that is wound tightly enough to limit the current drain and sized large enough to provide for adequate heat dissipation. The resulting magnetic field draws the plunger from its unpowered, extended position to a seated position against a backstop or pole piece. Because the linear force on the plunger is nonlinear with position, the force is relatively high immediately adjacent to the seated position and declines rapidly with increased distance from the seated position. Continuous duty linear solenoids are considerably larger than intermittent devices and often feature a two-coil design that provides greater pull-and-hold strength than single-coil devices of the same design. For linear solenoids that are capable of both continuous and intermittent duty, force ratings vary widely by duty cycle.

Performance specifications for continuous duty linear solenoids include maximum stroke, response time, holding force, power rating, power input, and latching. Maximum stroke is the full linear travel range of the plunger, from the fully extended position to the fully seated position. Typically, maximum stroke is measured in millimeters (mm). Response time is the time required to move the plunger full stroke under no-load conditions. Holding force is the force at zero-stroke, when the plunger is in the fully energized or seated position. Power rating is the input power for a specified winding at a specified voltage. Common DC power inputs are 3 VDC, 6 VDC, 12 VDC and 24 VDC. Common AC power inputs are 24 VAC, 115 VAC and 230 VAC. Some continuous duty linear solenoids use a permanent magnet to hold the plunger in the seated position without applied power. Others use two-way latching.

Continuous duty linear solenoids are available with a variety of features. Many are designed to protect the plunger or control its position. For example, protective boots are elastomeric bellows or sleeves that protect the plunger from harsh or contaminated environments. Hermetically sealed and intrinsically safe (IS) solenoids are also available. Return or compression springs are used to hold the plunger in the extended position when the solenoid is not powered. Variable position solenoids such as proportional devices can be positioned anywhere along the stroke. Integral encoders are used to indicate position. Internal derive electronics are used to regulate power, speed, range or motion. Continuous duty linear solenoids that UL Mark meet published safety standards from Underwriters Laboratories (UL). 

There are several frame styles for continuous duty linear solenoids. Tubular devices are enclosed in a tube-shaped casing and designed for applications with relatively long strokes. C-frame devices are often used in medical instrumentation, power management devices, computer peripherals and security applications. D-frame devices are suitable for small business machines. Open frame solenoids are low-cost solutions for many electromechanical applications, including computer peripheral equipment, business machines, security applications, and general instrumentation. Clappers or flappers are hinged solenoids for low-force, long-life applications. Solenoids with insulated, laminated frames minimize eddy currents.

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