A permanent magnet rotor arrangement comprising: a rotor drum having a radially outer surface ; a circumferential array of magnet carriers (8; 104) secured to the rotor drum for rotation therewith, each magnet carrier (8; 104) having a radially outer surface and a laminated construction; and at least one pole piece (10; 106) made of permanent magnet material located on the radially outer surface of each magnet carrier (8; 104); wherein the magnet carriers (8; 104) are mounted in abutment with each other in the circumferential direction to form a continuous, annular, magnet carrier assembly; wherein each magnet carrier (8; 104) extends axially along the rotor drum ; wherein each magnet carrier (8; 104) is releasably affixed to the rotor drum by at least one non-magnetic fixing member (16; 112); wherein each magnet carrier (8; 104) is supported at both of its circumferential edges by one of: at least one non-magnetic support member , at least one magnetic support member integrally formed with the magnet carrier and wherein a non-magnetic spacer is positioned between each support member and the rotor drum to prevent magnetic flux from entering the rotor drum , and at least one magnetic support member integrally formed with the rotor drum and wherein a non-magnetic spacer is positioned between each support member and the magnet carrier to prevent magnetic flux from entering the rotor drum; wherein the non-magnetic fixing members (16; 112) and the support members (18; 114) space the magnet carriers (8; 104) apart from the radially outer surface of the rotor drum in the radial direction to define a space or void therebetween. a rotor drum having a radially outer surface ; a circumferential array of magnet carriers (8; 104) secured to the rotor drum for rotation therewith, each magnet carrier (8; 104) having a radially outer surface and a laminated construction; and at least one pole piece (10; 106) made of permanent magnet material located on the radially outer surface of each magnet carrier (8; 104); wherein the magnet carriers (8; 104) are mounted in abutment with each other in the circumferential direction to form a continuous, annular, magnet carrier assembly; wherein each magnet carrier (8; 104) extends axially along the rotor drum ; wherein each magnet carrier (8; 104) is releasably affixed to the rotor drum by at least one non-magnetic fixing member (16; 112); wherein each magnet carrier (8; 104) is supported at both of its circumferential edges by one of: at least one non-magnetic support member , at least one magnetic support member integrally formed with the magnet carrier and wherein a non-magnetic spacer is positioned between each support member and the rotor drum to prevent magnetic flux from entering the rotor drum , and at least one magnetic support member integrally formed with the rotor drum and wherein a non-magnetic spacer is positioned between each support member and the magnet carrier to prevent magnetic flux from entering the rotor drum; at least one non-magnetic support member , at least one magnetic support member integrally formed with the magnet carrier and wherein a non-magnetic spacer is positioned between each support member and the rotor drum to prevent magnetic flux from entering the rotor drum , and at least one magnetic support member integrally formed with the rotor drum and wherein a non-magnetic spacer is positioned between each support member and the magnet carrier to prevent magnetic flux from entering the rotor drum; wherein the non-magnetic fixing members (16; 112) and the support members (18; 114) space the magnet carriers (8; 104) apart from the radially outer surface of the rotor drum in the radial direction to define a space or void therebetween. <EOS>