Description of Testrig

The tubular machine was mounted horizontally and powered by a 225 mm length crank arm coupled to a 1:40 step down gearbox driven by a two pole induction machine. Varying the length of crank and motor speed allows the generator to be tested for different peak speeds and oscillation amplitudes.

The presence of exceptionally large strong magnets caused many problems when handling and manufacturing the translator. It was constructed in-situ on the 20 mm diameter stainless steel support rod, with the magnets and steel spacers mounted alternatively, Figure 5.28. Care was required when adding the steel components, because the large attractive magnetic force in combination with the brittle Nd-Fe-B was conducive to damaging the magnets. A metal jig was manufactured, capable of lowering the parts together, but again the brittle nature of the magnets prevented its successful use. A series of wooden spacers was settled on as the most reliable method of drawing the components close to each other whilst preventing a high speed collision.

Figure 5.28: Tubular machine translator

An interesting effect was observed when the magnetic pieces were lowered onto the translator. At gaps of greater than 20 mm a strong repulsive force was observed, yet at a gap length of less than 20 mm this was rapidly replaced with a strong attractive force. At the larger gap lengths the new magnet was being repelled by the presence of like flux driven through the end mounted steel piece by the previously mounted magnet. At close proximity, however, the attractive force between the new magnet and the non saturated steel starts to dominate. This has a particularly significant consequence for disassembly.

Figure 5.29: Mechanical excitation of translator

The stator body is a 15 mm wall thickness plastic tube with the stator coils suspended on the inside. Each individual coil consists of 230 turns of 1 mm diameter copper wire bound together by glass tape. Every third coil has a 6 mm nylon spacer mounted to the inside of the tube. The mounting points of the spacer serve to react force from the coils and ensure that the three coils represent exactly one translator pole width to ensure a three phase output. Great care was taken not to have any supporting metal closer to the translator then the coils. The tube was secured to an aluminium frame by in-house manufactured brass bolts, Figure 5.30.

The rigid connection between driving motor and driven translator, Figure 5.29, allows for the derivation of a simple model to describe the machine's motion. Figure 5.31 shows a schematic diagram of the crank rod arrangement.

Figure 5.30: Photograph of prototype

Figure 5.31: Geometric picture of crank arrangement It is a simple geometric problem to describe the resulting motion, Equation (5.19). Analytical differentiation of this relationship gives a term for velocity, (5.23), thus avoiding the need for numerical differentiation routines in the performance model.

Figure 5.31: Geometric picture of crank arrangement It is a simple geometric problem to describe the resulting motion, Equation (5.19). Analytical differentiation of this relationship gives a term for velocity, (5.23), thus avoiding the need for numerical differentiation routines in the performance model.

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