Jonathan Z. Bird

Analysis of a magnetically geared lead screw

Linear magnetic gearboxes (LMG) and magnetic lead screws (MLS) have been shown to be capable of operating at significantly higher volumetric force densities than traditional electromagnetic linear actuators (ELA). However in both such devices the linear translator must be made of magnet material and therefore if the stroke length of the translator is long the cost of the MLS and LMG will become prohibitively high. In this paper a magnetically geared lead screw (MGLS) is investigated and its performance capability is compared with the LMG and MLS. The advantage of the MGLS is that the translator does not contain magnets.

Designing the first stage of a series connected multistage coaxial magnetic gearbox for a wind turbine demonstrator

The design of the first stage of a 59:1 multistage magnetic gearbox for a wind turbine demonstrator is presented. The multistage magnetic gearbox (MSMG) is composed of a two stage magnetic gearbox (MG). The first stage of the MSMG has a gear ratio of 6.45. A spoke type MG rotor typology is used with a unique segmented fully laminated rotor structure. Axially segmented magnets and a unique set of radial deflection rotor support rings are utilized.

Ideal Radial Permanent Magnet Coupling Torque Density Analysis

This paper derives the closed form 3-D analytical torque equations for an ideal radial Halbach rotor magnetic coupling. The performance of the radial Halbach coupling is then compared with an ideal axial Halbach rotor coupling. The closed form equations and comparison gives insight into the upper torque density limits of Nd-Fe-B based magnetic devices.

Analysis and Testing of a Coaxial Magnetic Gearbox With Flux Concentration Halbach Rotors

Halbach array magnetic gearboxes have been discussed as being able to create high torque density. However, Halbach arrays are difficult to mechanically assemble, and often the effective air gap must be made larger to provide space for a retaining sleeve. This paper investigates the benefits of using an additional ferromagnetic retaining pole within the Halbach array structure. It is shown that utilizing this flux concentration ferromagnetic pole improves the torque density and can also help retain the magnets in place.

A 3-D analytical model of a Halbach axial magnetic coupling

A 3-D analytical model is presented for a Halbach axial magnetic coupling. The field and torque are determined by first solving a 2-D field problem at the radial location in which the radial flux density is assumed zero. The solution to the 2-D problem is then incorporated into a 3-D magnetic charge sheet model so as to enable the complete 3-D fields and torque to be accurately computed. The presented model is compared with a 3-D finite element analysis model. The new 3-D field and torque analysis approach can be extended to model other 3-D axial magnetic devices.

A low assembly cost coaxial magnetic gearbox

This paper presents the design investigation and experimental testing of a flux-focusing magnetic gearbox with a three piece laminated rotor structure. Each rotor is made of a single lamination stack held together via thin lamination bridges. It is calculated that mechanical bridges reduces the torque density from 156Nm/L to 139Nm/L (a reduction of 11%). The experimentally measured torque density is shown to be only 95Nm/L because the magnets were demagnetized during testing.

A Magnetic Gearbox With an Active Region Torque Density of 239 N·m/L

In this paper, a 1:4.25 ratio ferrite magnet and Nd-Fe-B magnet flux-focusing magnetic gearbox with a high pole count is analyzed. A simple parameter sweep analysis is used to show that higher than previously published torque density values are achievable. Experimental results are then presented for the Nd-Fe-B design that confirm the calculations and also demonstrate that the proposed magnetic gearbox can operate with a low torque ripple.

Analysis and testing of a hybrid Halbach magnetic gearbox

Magnetic gearboxes (MG) utilize magnetic field heterodyning to create speed change without physical contact [1, 2].

Design and experimental testing of a magnetically geared lead screw

Linear actuation can be achieved using the magnetic gearing concept.

A low cost magnetically geared lead screw

Electromagnetic linear actuator (ELAs) have the advantage over hydraulic and mechanical mechanisms of being able to operate with higher efficiencies and are potentially more reliable.