Which Devices Converts Electrical Energy Into Mechanical Energy?

Converting electrical energy into mechanical energy is an important process utilized in many applications and devices. From small electronics to large industrial equipment, being able to convert electricity into motion allows us to power machines and automate processes. This conversion is made possible through various mechanisms that link electrical inputs to physical outputs.

In this article, we will provide an overview of the main types of devices that can convert electrical energy into mechanical energy. We will look at how electric motors, solenoids, electromagnets, piezoelectric actuators, shape memory alloys, electroactive polymers, electrohydrodynamic actuators, ionic polymer-metal composites and other devices are able to produce motion from electricity through clever engineering and application of physics principles.

Table of Contents

Electric Motors

Electric motors are devices that convert electrical energy into mechanical energy by harnessing electromagnetism. They operate on the interactions between magnetic fields and current carrying conductors.

There are two main types of electric motors – AC (alternating current) motors and DC (direct current) motors. In an AC motor, the rotating magnetic field is produced by alternating currents that are fed into the stator windings. The rotating magnetic field induces a current in the rotor, resulting in a torque that causes the rotor to turn. AC motors include induction motors, synchronous motors, and wound rotor motors.

In a DC motor, direct current flows through the armature coil, generating a magnetic field that interacts with the stationary magnetic field from the permanent magnets or electromagnets in the stator. This produces a torque that rotates the armature. The speed of a DC motor can be easily controlled by varying the voltage fed to the armature. Types of DC motors include brushed DC motors, brushless DC motors, and stepper motors.

So in summary, electric motors utilize the forces created by magnetic fields to continually convert electricity into rotational kinetic energy. Their simplicity and controllability make them an indispensable technology for a wide variety of applications.

Solenoids

A solenoid is an electromagnetic device that converts electrical energy into linear mechanical motion. It consists of a coil wound around a movable iron core. When electric current is passed through the coil, a magnetic field is generated which pulls the iron core into the center of the coil. The key components of a solenoid include:

Coil – Made of insulated copper wire wound around a cylindrical tube. The number of turns determines the strength of the magnetic field.

Iron Core – Typically made of soft iron and slides back and forth in the tube when the coil is energized and de-energized.
Housing – Encloses the coil and provides a mounting point for attachments and linkages.
Return Spring – Pulls the core back to its original position when power is removed.

Solenoids are widely used to convert electric signals into linear mechanical motion and provide push/pull force. Common applications include:

Opening and closing valves in fluid control systems.
Driving mechanical switches and circuit breakers.

Actuating locks, latches, and releases in access control systems.
Operating pneumatic valves to control air cylinders.
Driving mechanical linkages in vending machines.

In summary, solenoids are simple and compact electromagnetic actuators ideal for pushing, pulling, opening and closing applications. Their linear motion allows precise control and quick response.

Electromagnets

Electromagnets utilize electricity flowing through a coil to generate a magnetic field that can be turned on or off as needed. Unlike permanent magnets, electromagnets only produce a magnetic field when electric current is flowing through the coil. The strength of the magnetic field can be easily adjusted by changing the amount of electric current.

Electromagnets consist of a coil of wire wrapped around a ferromagnetic core made of iron or steel. When electric current passes through the coil, it creates a magnetic field oriented along the coil’s axis. The ferromagnetic core serves to concentrate and amplify the magnetic field. More wraps in the coil and higher electric current result in a stronger magnetic field.

A major advantage of electromagnets is that the magnetic field can be quickly changed by controlling the electric current. This allows them to be used in applications where the magnet needs to be turned on and off. For example, electromagnets are used in cranes to pick up and release scrap metal by energizing and de-energizing the magnet. They are also used in relays, which use an electromagnet to actuate a switch and control a high-power circuit.

Overall, electromagnets leverage electricity to generate controllable and adjustable magnetic fields. This allows them to convert electrical energy into mechanical force for applications like lifting, holding, and moving ferromagnetic objects. Their ability to be energized and de-energized makes them uniquely suited for mechanical tasks that require starting and stopping magnetic force.

Piezoelectric Actuators

Piezoelectric actuators convert electrical energy into mechanical energy using the piezoelectric effect. The piezoelectric effect causes certain materials, like crystals and ceramics, to generate an electric charge under mechanical stress. This process can also work in reverse – when an electric field is applied to a piezoelectric material, it induces a mechanical deformation or vibration.

Piezoelectric actuators utilize this reverse piezoelectric effect to generate forces and motion from electrical signals. They are made from materials like lead zirconate titanate (PZT) and polyvinylidene fluoride (PVDF). When a voltage is applied to a piezoelectric actuator, it creates mechanical strain and deformation which can be precisely controlled by the voltage level.

Due to their strong forces, fast response times, and high precision, piezoelectric actuators have many applications. They are commonly used in precision positioning equipment, adaptive optics, printers, and sensors. Ultrasonic piezoelectric transducers are used for medical imaging, industrial nondestructive testing, and generating vibrations in consumer devices.

Shape Memory Alloys

Shape memory alloys (SMAs) are metals that have the ability to return to their original “remembered” shape when heated. This shape changing effect occurs due to temperature and stress-induced phase transformations in the material’s crystal structure.

The most common SMA is an alloy of nickel and titanium called Nitinol. Below its transformation temperature, Nitinol is martensitic and can be easily deformed. When heated above its transformation temperature, it reverts to its austenitic structure and recovers its original shape.

When an electric current is passed through Nitinol wire, resistive heating causes the wire to contract and do work. This ability to convert electrical energy into mechanical energy makes SMAs useful for many applications:

Actuators – SMA wires provide simple, quiet and lightweight actuators for opening/closing valves or moving robotic joints.

Artificial Muscles – SMA actuators can simulate natural muscle movements for biomimetic robots and prosthetic limbs.
Microgrippers – Miniature Nitinol grippers open and close when heated, enabling precise picking-and-placing of small objects.
Self-Expanding Stents – Nitinol’s ability to expand and stiffen at body temperature makes it ideal for minimally invasive medical devices.

With their solid-state design and silent operation, SMA actuators are ideal for applications where electrical energy needs to be converted into smooth, controlled mechanical motion.

Electroactive Polymers

Electroactive polymers (EAPs) are a class of smart materials that produce mechanical displacement and motion when stimulated electrically. They essentially act as artificial muscles that can push, pull, bend, and rotate in response to voltage changes. EAP materials consist of two thin layers of conductive electrode layers sandwiching an active polymer film. When an electric field is applied across the electrodes, the polymer film is distorted and deformed due to electrostatic interactions between the polymer chains. This deformation can create expansion, contraction, bending or rotation.

Some common types of electroactive polymers include:

Dielectric elastomer actuators – made of elastomeric polymers that stretch and deform when stimulated.
Ionic polymer metal composites – contain ionic polymer gels that bend when electrically activated due to ion migration.
Conductive polymers – change size and shape when electrochemically oxidized or reduced.

Key advantages of EAPs include their soft, flexible structure that mimics natural muscle movements, low density, and ability to operate quietly with no gears or motors. Potential applications include artificial muscles for robots and prosthetics, pumps, sensors, speakers, haptic interfaces and biomimetic devices. Overall, electroactive polymers provide a versatile way to create mechanical motion directly from electrical inputs.

Electrohydrodynamic Actuators

Electrohydrodynamic actuators utilize electrostatic forces to manipulate fluids and induce motion. They operate based on the principle that an electric field applied to a dielectric fluid will induce a flow in the fluid through a phenomenon known as electrohydrodynamic thrust. This allows them to convert electrical energy into kinetic energy.

One common example is the electrohydrodynamic thrustor or ionocraft. This consists of two asymmetric electrodes, one thin wire and one plate. When a high voltage is applied between the electrodes, it ionizes the surrounding air and creates an ionic wind. The force created by this wind can produce thrust and cause the device to lift off the ground.

Other examples include electrohydrodynamic pumps, which can pump fluids without any moving parts, and electrohydrodynamic speakers, which induce vibrations and sound waves in liquids by applying an electric field. Electrohydrodynamic actuators have advantages of no moving parts, high responsiveness, and the ability to manipulate fluids on very small scales.

Research is ongoing into maximizing their force output and efficiency for applications ranging from propulsion to microfluidics. They represent a novel way of inducing motion directly from electrical input.

Ionic Polymer-Metal Composites

Ionic polymer-metal composites (IPMCs) are an emerging class of electroactive polymers that can generate a mechanical bending motion in response to an applied voltage. They are composed of an ionic polymer membrane, typically Nafion or Flemion, that is coated or plated with conductive metal electrodes on both sides, usually gold or platinum.

When an electric field is applied across the IPMC, the cations within the polymer membrane migrate towards the cathode, causing that region to expand. This creates a bending motion towards the anode. Reversing the voltage polarity causes the IPMC to flex in the opposite direction. The response time is very fast, on the order of milliseconds, allowing for high-frequency actuation.

IPMCs require low voltages (1-5V) and exhibit large bending deformations. Their flexibility, low mass density, and ability to operate in wet environments make them well-suited for bioinspired robotic applications. Some example uses include artificial muscles, grippers, swimmers, valves, and sensors. Ongoing research aims to improve their durability and performance for real-world applications.

Conclusion

This article covered various devices that are able to convert electrical energy into mechanical force and motion. From electric motors and solenoids to more advanced technologies like electroactive polymers, we explored the different ways electricity can be harnessed to create movement.

The ability to convert electricity into kinetic energy is extremely important in numerous applications. Electric motors power a wide range of devices we use every day, from home appliances to industrial machinery. More specialized actuators like piezoelectrics and shape memory alloys enable advanced robotics and other automated systems. New smart materials like ionic polymer-metal composites continue to push the boundaries of what’s possible.

Overall, the ingenious ability to translate electrons into real-world motion and mechanics has been essential to technological progress. As researchers uncover new properties of materials and engineers creatively apply these discoveries, the future will surely hold even more innovative methods of electric-to-mechanical energy conversion.