The sealing of the VHM translator is troublesome because of its toothed cross section. In order to use a conventional contact seal it is necessary to have a uniform cross section, which could be achieved by encasing the translator in a magnetically inert material as shown in Figure 6.10. The rotor slots would be filled to the same height as the teeth thus providing a flat surface for the seal to contact against, without influencing the overall magnetic properties.

Figure 6.10: Filling the translator slots

As drawn, the translator has a rectangular cross section with sharp edges, still representing problems in terms of sealing. It may be possible to avoid this by giving the outer surface of the fill material a smooth profile. A ceramic material would have the correct magnetic properties whilst being sufficiently hard and smooth to be used as a sealing surface. In this configuration, there is scope for flexibility with the endstops as large amplitude oscillation will break the seal of the stator case, but should not permanently damage the machine itself.

To avoid the use of a filler material, and utilise traditional cylindrical seals like those used in a hydraulic ram, it is necessary to transfer the motion of the translator to a cylindrical shaft. The electrical machine would need mounting in an oversized chamber which extended to the extremities of the motion, as shown in Figure 6.11.

Figure 6.11: Cylindrical sealing for the VHM

An inherent feature of this design is the need for stringent endstops, as allowing the translator to extend too far would likely cause catastrophic damage to the outer case. Furthermore, the size of the entire stator must now be equal to that of the active area plus the maximum permissible amplitude. One possibility is that the entire air filled chamber incorporating the stator could be used to house the power electronic equipment necessary for VHM machines. Alternatively it could just be used for buoyancy and help offset the likely weight penalty of using direct drive.

Renewable Energy Eco Friendly

Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

Get My Free Ebook

Post a comment