Micro linear electromagnetic actuators' definition and principle
Miniature linear solenoid actuators are compact electromechanical devices that make it to convert electrical energy into linear (straight-line) mechanical motion. Unlike larger linear solenoids, they are distinguished by their small size (typically a few millimeters to a few centimeters in length/diameter) and low power consumption, making them ideal for applications where space, weight, and energy efficiency are critical.
- Core Definition
Essentially, a micro linear solenoid actuator is a scaled-down version of a linear solenoid optimized for small-scale linear actuation. It consists of three key components:
Stationary Coil: A thin, insulated copper wire wound on a bobbin (usually made of plastic or ceramic) that generates a magnetic field when electricity is passed through it.
Plunger: A ferromagnetic core (e.g., iron, steel) that slides axially (back and forth) within the magnetic field of the coil.
Return mechanism: A small spring (or in some cases a permanent magnet) that returns the plunger to its original position when the coil is de-energized.
Their primary function is to generate short-stroke linear motion (typically 0.5–10 mm) and moderate forces (typically 1–50 N), depending on design and power input.
- Working Principle
The operation of a micro linear solenoid actuator relies on electromagnetic induction and the interaction between a magnetic field and a ferromagnetic material. This process can be broken down into four key steps:
De-energized state: When no current flows through the coil, the plunger is held in the "rest position" by the return spring (or permanent magnet). At this point, there is no magnetic force acting on the plunger, so it remains stationary.
Power On: When direct current (DC) is applied to the coil, it generates a uniform magnetic field around its axis (according to Ampere's law). This magnetic field magnetizes the ferromagnetic plunger, turning it into a temporary magnet.
Magnetic Attraction and Linear Motion: The magnetized plunger is pulled toward the center of the coil (the area of greatest flux density) to minimize the reluctance (resistance to magnetic flux) of the magnetic circuit. This attractive force forces the plunger to slide axially (linearly) outward or inward (depending on the design) to perform the desired motion (e.g., push a valve, close a switch).
Power-off reset: When the current is cut off, the coil magnetic field disappears. The return spring pushes the plunger back to its initial position, ready for the next cycle.
NOTE: Some designs use a "bipolar" coil (reversing the direction of the current) to achieve bidirectional motion, eliminating the need for a spring.
