One of the most significant discoveries in the field of electricity is the discovery of electromagnetism. The primary uses of electromagnetism are in motors and the generation of electrical power, which have proven to be great enablers for other innovations.

An electromagnet is a magnet whose magnetic energy is generated by the electric current flow. Some electromagnets are so large and powerful that they can lift tons of scrap metal at one time. Other electromagnets used in some electrical and electronic circuits, such as those located in relays and solenoids, are small.

Electromagnetic brake

Electromagnets are often used in conjunction with an electric motor, especially a lifting motor as used on a crane. When the lifting motor is engaged, a solenoid releases a brake, allowing the lifting drum to rotate and wind up the load.

Disconnecting the motor, even if through power failure, releases the solenoid and automatically applies the brake. Thus, the system is considered failsafe as loss of power does not permit the load to fall.

Electromagnetic brakes can also be made to operate when power is applied, either when a control circuit applies energy or the operator presses a button or footswitch.

Electro-dynamic braking, which will also be discussed later in this text, involves an electric motor connected in such a manner as to make its operating speed zero, so when the motor is energized, it attempts to stop whatever load it is connected to.

Electromagnetic clutch engages a flywheel in electric motors to the cutting blade for one revolution of the flywheel. Source: AdobeStock Electromagnetic clutch engages a flywheel in electric motors to the cutting blade for one revolution of the flywheel. Source: AdobeStock

Electromagnetic clutch

At times, an electric motor cannot speed up or slow down fast enough for a given load. A typical situation is a large metal-working guillotine. The electric motor runs a large flywheel up to speed, and when the press is operated, an electromagnetic clutch engages the flywheel to the cutting blade for one revolution of the flywheel. The flywheel provides most of the energy for the cut, and when completed, the motor drives the flywheel back up to its idling speed.

Many other machines use an electric clutch to engage or disengage various functions of the machine, often multiple functions from a single driving motor.

Electromagnetic chuck

An electromagnetic chuck is an electrically operated device for holding work on a machine. On a grinding machine, for example, an iron part might be held in place by placing it on the surface of the chuck and applying power to the magnet. A disadvantage is that the power supply must be very reliable as loss of magnetism can result in major damage to the machine. The system is, therefore, mostly used to add security to a holding mechanism where the job is unlikely to move anyway. Often the machine is a computer numerical controlled (CNC) machine.

Lifting electromagnet

Scrap metal dealers often need to move large amounts of jagged and dangerous iron and steel. To manually handle the material would be dangerous, and even ropes and lifting straps might be damaged by the scrap. The answer is to use electromagnets to pick up all sorts of metal scrap in all sizes.

The magnet is lowered onto the scrap, energized and lifted away to wherever the scrap is intended to be placed, and then de-energized to drop the scrap. Some electromagnets can lift many tons of iron in one lift, including large automobiles.

Electromagnetic separator

Electromagnets only work on magnetic materials; therefore, the effect can be used to separate magnetic materials from non-magnetic materials. Typically, a conveyor belt carries materials to a dumping bin, but the end drum is magnetized, so magnetic materials fold around to the underside of the drum, where they drop off into a separate bin. Other methods exist, depending on the type of materials being separated.

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