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The permanent
magnet motor, also referred to as a "canstack" motor, has,
as the name implies, a permanent magnet rotor. It is a
relatively low speed, low torque device with large step
angles of either 45 or 90 degrees. It's simple construction
and low cost make it an ideal choice for non industrial
applications, such as a line printer print wheel positioner.
Unlike the other stepping
motors, the PM motor rotor has no teeth and is designed to
be magnetized at a right angle to it's axis. The above
illustration shows a simple, 90 degree PM motor with four
phases (A-D). Applying current to each phase in sequence
will cause the rotor to rotate by adjusting to the changing
magnetic fields. Although it operates at fairly low speed
the PM motor has a relatively high torque characteristic. |
