Slotless construction for small synchronous motors using samarium cobalt magnets

Rare-earth magnet materials offer the possibility of slotless designs for miniature motors. Comparative analyses of slotted and slotless designs are presented for 2-pole permanent-magnet synchronous motors where the magnet has a linear demagnetisation characteristic. Experimental results are given for the magnet field of the slotless design in which the magnet end effect is considered. Results from an experimental slotless motor having a plastics-bonded rare-earth magnet rotor are included.