Branch 68

Mt Noble wind generator details.

The picture of the present day generator is driven by a eight bladed multi-wing prop and hub, the blade angle is set at 45°. The prop will start rotating in a breeze of 20kph, (because of permanent magnet resistance) giving .25 amps, the diameter of the assembled prop 640 mm, it will produce 6 amps at 110 kph windspeed. The wind blows, 90% of the time from the north-west so the generator is fixed in this position, which gets round the problem associated with noise produced by using slip rings on a 360° swivelling generator, interfering with the repeaters receivers.

The motor was manufactured by General Electric and the New Zealand manufacturer has installed them into their gentle annie washing machines. The motor was designed as a stepper motor for direct drive agitation purposes,. The rotor is permanent magnet, which means there is no noise from brushes. I have used three of the windings, because the fourth winding was used as a breaking system on shutdown from spin mode having a different number of turns. Each phase is fed separately through a bridge rectifier and finally an in-line fuse. The whole thing is housed in 6 inch PVC tubing with end caps this helps keep it dry from high winds with rain. There is a small air scoop at the bottom front of the generator and several 12 mm holes at the rear bottom, giving ventilation. The generator is mounted inside the PVC tubing, with two 2 x1/8 inch copperplate helping to conduct away the heat and giving good mount points for the bridge rectifies.

Performance of the generator was measured by bolting it to a plank and mounting it on top of a van roof and selecting the appropriate road in a rural area. Different prop diameters and blade angles were tried from four blades through to eight also blade angles from 30° to 45°. Six blades, at 45° gave a start rotation speed of 30 kph, with better top end performance, but I decided to stay with the eight which gave start rotation of 20 kph.

The testing of this generator was done by the late Bill Whitley ZL3AHN and, myself, Mark Chilton ZL3AIC.