Electric machine

Abstract

An electric machine comprising a first carrier having an array of electromagnetic elements and a second carrier having electromagnetic elements defining magnetic poles, the second carrier being arranged to move relative to the first carrier. An airgap is provided between the first carrier and the second carrier. The electromagnetic elements of the first carrier include posts, with slots between the posts, one or more electric conductors in each slot, the posts of the first carrier having a post height in mm. The first carrier and the second carrier together define a size of the electric machine. The magnetic poles having a pole pitch in mm. The size of the motor, pole pitch and post height are selected to fall within a region in a space defined by size, pole pitch and post height that provides a benefit in terms of force or torque per weight per excitation level.

1 . A radial flux electric machine, comprising:
 a first carrier having an array of electromagnetic elements;   a second carrier comprising electromagnetic elements, the second carrier being arranged to move relative to the first carrier and having an outer edge;   an airgap between the first carrier and the second carrier, the machine having an airgap diameter; wherein the size of the electric machine is the airgap diameter;   the electromagnetic elements of the first carrier including posts, with slots between the posts, the slots having one or more electric conductors in each slot;   the second carrier comprising a rigid element and posts, with slots between the posts, the slots having at least one permanent magnet in each slot and wherein the posts comprise extensions of the rigid element; and   wherein the posts of the second carrier comprise a relief at the outer edge to retain the permanent magnets.   
     
     
         2 . The electric machine of  claim 1 , in which the electric conductors comprise either a concentrated winding, or a distributed winding. 
     
     
         3 . The electric machine of  claim 1 , in which the first carrier comprises a stator formed of a unitary piece of magnetically susceptible material, each post comprising a portion of the stator, and preferably in which the stator comprises a material with no measurable creep below 1.378951*10 8  Pascals. 
     
     
         4 . The electrical machine of  claim 3  in which the posts each have a tangential width and the stator comprises a backiron portion, the backiron portion having a thickness equal to or less than the tangential width of the posts. 
     
     
         5 . The electrical machine of either of  claim 3  or  4  in which the posts each have a tangential width and the stator comprises a backiron portion, the backiron portion having a thickness equal to or less than half the tangential width of the posts. 
     
     
         6 . The electric machine of  claim 1  in which the airgap diameter is from 25.4 micrometers to 254 micrometers. 
     
     
         7 . The electric machine of  claim 1  in which the electric machine is a frameless electric machine. 
     
     
         8 . The electric machine of  claim 1 , in which the second carrier comprises motor laminations. 
     
     
         9 . The electric machine of  claim 8 , in which each of the motor laminations has a thickness between about 0.015″ and about 0.025″. 
     
     
         10 . The electric machine of  claim 1 , in which the second carrier has a slot density between about 0.16 and about 0.5. 
     
     
         11 . The electric machine of  claim 1  having a cooling channel adjacent the first carrier. 
     
     
         12 . A radial flux electric machine, comprising:
 a first carrier having an array of electromagnetic elements;   a second carrier comprising electromagnetic elements, the second carrier being arranged to move relative to the first carrier and having an outer edge;   an airgap between the first carrier and the second carrier, the machine having an airgap diameter; wherein the size of the electric machine is the airgap diameter;   the electromagnetic elements of the first carrier including posts, with slots between the posts, the slots having one or more electric conductors in each slot;   the second carrier comprising a rigid element and posts, with slots between the posts, the slots having at least one permanent magnet in each slot and wherein the posts comprise extensions of the rigid element, wherein the posts of the second carrier comprise a relief at the outer edge to retain the permanent magnets; and   wherein the electromagnetic elements of the first carrier and the second carrier are arranged so that a greater portion of magnetic flux flows through the rigid element than flows through the air gap.