Permanent magnet types have some performance advantages over electromagnets, and have become predominant in fractional horsepower applications. They are smaller, lighter, more efficient and reliable.
Originally all large industrial DC motors used wound field or rotor magnets. Permanent magnets have traditionally only been useful on small motors because it was difficult to find a material capable of retaining such ahigh-strength field. Only recently have advances in materials technology allowed the creation of high-intensity permanent magnets, such as neodymium magnets, allowing the development of compact, high-powermotors without any field coils.