Machine Design

Low-cost alternative to ironless-core motors

New 22-mm iron-core motors use smaller, more powerful neodymium magnets, allowing for a larger, heavier iron armature than typically used in ironless-core motors.

A new 22-mm iron-core motor features a brush end bell that incorporates a printed-circuit board as well as RFI-suppression components. The RFI-suppression components are placed inside next to the noise source — the brushes — which greatly reduces RFI emissions. Because the motors use powerful neodymium magnets, as opposed to conventional ceramic magnets, less magnet material is needed. This let designers allocate more space for the iron armature that is larger and heavier than typical armatures in ironless-core motors. The larger rotor in the motor puts more power in a smaller package.

Another design feature increases brush life. Typical ironless-core motors use cantilevered springs which can place excessive forces on brushes, and cause wear. The redesigned cartridge brush uses spring loading that optimizes brush force throughout the life of the motor. The assembly varies the force on the brushes, from the beginning of the motor's life to the end of brush life, providing just enough push on any remaining brush material until it is completely gone.

The motors and gearmotors are available in two lengths — 1.256 and 1.556 in. — and provide peak torques up to 5.3 oz-in. with speeds of more than 8,000 rpm. They can be customized with rear-exiting leads or terminals, optical encoders, and other options.

Portions of this article were contributed by John Marks, Pittman Engineering, 343 Godshall Dr., Harleysville, PA 19438-0003, (877) 748-8626, fax: (215) 256-1338,

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