Electromagnets use electric current to generate a magnetic field which can be turned on or off as needed. They are made from a softer iron which quickly dissipates the induced magnetism after the current is switched off.

Electromagnetic strength is dependent on a variety of factors, such as the number of coils in the electrical wire that generates the power, the applied current, and the core material’s magnetic permeability.

Categories of electromagnets include:

• Flat-faced
• Parallel pole
• Standard lifting
• Suspension
• Laboratory
• Permanent

Flat and Parallel Pole Magnets

Flat-faced electromagnets and parallel-pole magnets are two common types of electromagnets.

• Flat-faced magnets are used when the entire face of the magnet is in direct contact with a smooth, flat surface.
• Parallel-pole electromagnets or bi-polar magnets have two widely-spaced poles which allow the magnetic field to have a greater reach.

These electromagnets are used when the magnet has only partial contact with the surface. They are also used to handle irregular shapes, or to work through an air gap.

Lifting or Suspension Magnets

Standard lifting magnets and suspension magnets are commonly available:

• Standard electromagnets are designed to lift sold, compact materials instead of scraps or small parts. Compact materials for standard lifting magnets include billets, steel plates, bars, and forgings.

• Suspension magnets are powerful electromagnets that are used for heavy or odd-shaped magnetic materials. These electromagnets are often used in process manufacturing, material handling, or scrap-yard use.

Laboratory and Permanent Magnets

Other types of electromagnets include laboratory electromagnets and permanent or electromagnet combinations:

• Laboratory electromagnets are used in research labs. Common configurations for these electromagnets are dipole, quadrupole, and sextuple electromagnets.

• Permanent or electromagnet combination magnets provide safe load-handling, even when power is accidentally removed from the target.

Applications

Electromagnets are used to lift and suspend objects in various applications, typically large amounts of ferrous materials such as scrap iron. Electromagnets are also used in the design of industrial and consumer products such as:

• Electric generators
• Electric motors
• Doorbells
• Circuit breakers
• Televisions
• Loudspeakers
• Brakes

• Clutches

Superconducting Electromagnets

Special superconducting electromagnets generate powerful magnetic fields with little energy waste. Consequently, superconductor electromagnets are used in transportation applications, including space travel and maglev trains. Specialized electromagnets are also available from some electromagnet suppliers.

Standards

A-A-55143/1 - Relays, electromagnetic, general purpose 10 amperes, 1-3pdt, ac and dc coils, socket mount.

GMW3091 - General specification for vehicles, electromagnetic compatibility.

SAE ARP1267 - Electromagnetic interference measurement impulse generators; standard calibration requirements and techniques.

Image Credits:

Dexter Magnetic Technologies, Inc. | Industrial Magnetics, Inc. | SG Transmission