Method of construction for permanent magnet generator
A generator comprises as a first part a stack of disc-like annular rotors spaced one from the other and coaxially located upon and rotating with an elongate central member each rotor having an inner annular portion and an outer annular portion, the outer annular portion bearing and/or comprising a magnetic annulus, one or more spacers being coaxially mounted around the central member in between the inner annular portions of each rotor and abutting against them in such manner such as to brace them to remain orthogonal to the longitudinal axis of the assembly as well as providing the required spacing therebetween, and as a second part, a stack of annular stators interposed between the rotors and mounted over the spacers but having an inner clearance diameter greater than that of the outer diameter of the portion of spacer over which they are located.
1. A wind turbine generator comprises as a first part a stack of disc-like annular rotors spaced one from the other and rotating with an elongate central member each rotor having an inner annular portion coaxial with and spaced apart from the elongate central member and an outer annular portion, the outer annular portion bearing and/or comprising a magnetic annulus, one or more spacers being coaxially mounted around the elongate central member in between the inner annular portions of each rotor and abutting against them in such manner such as to brace them to remain orthogonal to the longitudinal axis of the assembly as well as providing the required spacing therebetween, and the first part further comprising outer discs sandwiching the rotors and the spacers and a plurality of bolts passing through the first part and holding the spacers in contact with the rotors, the outer discs connected to the central axis, the outer discs and the bolts transferring all of the torque from the rotors to the elongate central member, and as a second part, a stack of annular stators interposed between the rotors and mounted over the spacers but having an inner clearance diameter greater than that of the outer diameter of the portion of spacer over which they are located, wherein the diameter of the cross section of the spacers at a longitudinal position corresponding to a stator is less than the diameter of portions of spacers pressing against sides of the rotors.
2. A generator according to claim 1 wherein the spacers comprise one of more tubular members.
3. A generator according to claim 1 wherein the elongate central member upon which the rotors are mounted is in the form of a cylinder.
4. A generator according to claim 1 wherein permanent magnets of the magnetic annulus abut against the spacer.
5. A generator according to claim 1 , wherein the outer diameter of the spacers is at least half, preferably at least two thirds of the outer diameter of the magnetic annulus.
6. A generator according to claim 1 , wherein the spacers and/or rotors are radially spaced from the elongate central member.
7. A generator according to claim 1 , wherein a distance between the central longitudinal axis of the first part and an inner diameter of the rotors and/or spacers is at least ½ of the outer radius of the rotors.