Comparative Study Between Mechanical and Magnetic Planetary Gears

Abstract

The paper deals with the possibility of replacing a mechanical planetary gear system by a magnetic planetary gearbox. The magnetic planetary gearbox has many advantages such as contact-free, no gear lubrication, high-speed-reduction ratio and high durability. Firstly, the principle of operation, design equations and Willis relation for the magnetic and the mechanical planetary gears are given. A comparative study between the two systems in terms of torque transmission capabilities is presented.Index Terms-Gearbox, high torque density, magnetic planetary gears, mechanical planetary gears, Willis equation. NOMENCLATURERelated to sun, planet, ring, and planet carrier gears respectively (mechanical gear).Related to inner rotor, steel pole pieces, outer rotor, and carrier steel pole pieces respectively (magnetic gear). Rotational velocity of the inner rotor and the sun gear.Rotational velocity of the planet gear.Rotational velocity of the outer rotor and the ring gear.Rotational velocity of the carrier steel pole pieces and the planet carrier.Basic train gear ratio.Number of teeth of the sun, the planet and the ring.Diameter of the sun, the planet and the ring.Outer diameter of the ring gear.Pitch circle diameter, base circle diameter.Input torque at the sun gear or at the inner rotor.Output torque at the ring gear or at the outer rotor.Torque at gear one (the sun gear).Gear ratio.Tangential force.Tangential force exerted by the planet on the sun teeth.

Gear ratio optimization of a full magnetic indirect drive chain for wind turbine applications

“…A hybrid excitation synchronous generator developed by Jeumont Electric [11]- [12] is integrated in the conversion chain after the last stage of gear (Fig.1). This topology potentially offers high performance and must be strongly optimized to give a hope of competitiveness compared to indirect drive with mechanical gears and even for high torque applications (offshore wind turbine for instance) [13]. Some magnetic gear drive optimization work has already been done on the magnetic parts masses of the magnetic gear [14]- [15].…”

“…the tangential flux (13). Comparison can then be drawn between the magnetic torque of the internal and external rings obtained with the analytical model and finite element model with a rotation of the internal ring while keeping the pole-piece ring and the external ring fixed (Fig.5).…”

Field-Oriented Control for an Induction-Machine-Based Electrical Variable Transmission

“…2a. Such a magnetic gear was proposed in [13], and can have a comparable power density as its mechanical counterpart according to [14]. Moreover, it has the advantage of high efficiency, absence of mechanical friction and wear, lower maintenance and inherent overload protection [15].…”

Analysis and Design Optimization of a Coaxial Surface-Mounted Permanent-Magnet Magnetic Gear

“…By adopting a coaxial arrangement of two PM rings, all of the PMs could contribute to the torque transmission simultaneously, hence a torque density exceeding 100 kNm/m 3 could be achieved [8]. A detailed comparison between the planetary mechanical and coaxial magnetic gears has been provided in [10], showing that coaxial magnetic gears could have comparable or better performance than their mechanical counterparts while avoiding many mechanical drawbacks. Some other comparisons in [7] and [11] indicate that the coaxial magnetic gears exhibit a remarkably improved efficiency with a comparable or smaller volume than some classical commercial mechanical gearboxes.…”