Basically, three types of magnets are used in PMDC motors: alnico
magnets, ceramic (or ferrite) magnets, and rare-earth magnets (samariumcobalt
magnets, for instance).
From Wikipedia: “Alnico is an acronym referring to a family of iron alloys
that, in addition to iron, are composed primarily of aluminum (Al), nickel (Ni),
and cobalt (Co), hence al-ni-co. They also include copper, and sometimes
titanium. Alnico alloys are ferromagnetic, with a high coercivity (resistance
to loss of magnetism) and are used to make permanent magnets. Before
the development of rare earth magnets in the 1970s, they were the
strongest type of magnet.
The composition of alnico alloys is typically 8–12% Al, 15–26% Ni, 5–24%
Co, up to 6% Cu, up to 1% Ti, and the balance is Fe. The development of
alnico began in 1931, when T. Mishima in Japan discovered that an alloy of
iron, nickel, and aluminum had a coercivity of 400 oersted (Oe; 32 kA/m),
double that of the best magnet steels of the time.
Basically, three types of magnets are used in PMDC motors: alnicomagnets, ceramic (or ferrite) magnets, and rare-earth magnets (samariumcobaltmagnets, for instance).From Wikipedia: “Alnico is an acronym referring to a family of iron alloysthat, in addition to iron, are composed primarily of aluminum (Al), nickel (Ni),and cobalt (Co), hence al-ni-co. They also include copper, and sometimestitanium. Alnico alloys are ferromagnetic, with a high coercivity (resistanceto loss of magnetism) and are used to make permanent magnets. Beforethe development of rare earth magnets in the 1970s, they were thestrongest type of magnet.The composition of alnico alloys is typically 8–12% Al, 15–26% Ni, 5–24%Co, up to 6% Cu, up to 1% Ti, and the balance is Fe. The development ofalnico began in 1931, when T. Mishima in Japan discovered that an alloy ofiron, nickel, and aluminum had a coercivity of 400 oersted (Oe; 32 kA/m),double that of the best magnet steels of the time.
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