I am ritired now for some years and I no longer need substantial income out of my activities for Kragten Design. Therefore I have halved the licence fees for the bigger VIRYA wind turbines for which a licence is required. The new licence fees can be found on the folder “Extended specification VIRYA windmills” which you find at the menu “VIRYA-folders”.
The VIRYA-3.18 with a Chinese axial flux generator and a 2-bladed steel rotor with a design tip speed ratio of 7 is cancelled. This is done because experiences with the 2-bladed steel rotor of the VIRYA-1.65 have shown that too much noise is produced for steel rotors with 7.14 % cambered blades if the design tip speed ratio is that high.
Report KD 532 gives the rotor calculations of a 3.1 m diameter, 2-bladed rotor made out of Roofmate and glass fibre. A new chapter 6 has been added in which it is checked if this rotor matches with the Chinese axial flux generator of Hefei Top Grand type TGET260-0.5KW-350R. As generator characteristics for a 24 V battery load are not available, these characteristics were estimated from the given specification of the manufacturer.
Report KD 595 with the measurements of a Chinese axial flux generator has slightly been reviewed. A reference 4 to the VIRYA-1.5 rotor has been added.
Report KD 634 has been added to the list of free public KD-reports. The title of this report is: Calculations executed for the 3-bladed rotor of the VIRYA-3.4 windmill (lambda design = 4.5, galvanised steel blades) driving a centrifugal pump through a Polycord transmission with i = 2.5 and a vertical shaft in the tower centre. Report KD 623 has been added to the references of report KD 490: Water pumping with a windmill.
The original pdf file of report KD 320 about the Polycord transmission of the VIRYA-2.8B4 was larger than 2 Mb and therefore it could not be added to my website completely. The data sheet of the Polycord transmission in between the rotor shaft and the vertical shaft was therefore removed. This data sheet has be scanned again but now on a lower resolution of 100 dpi and the report is now small enough to present it completely.
Onder het menu VIRYA-folders werd een Nederlandstalige folder toegevoegd van de zeven gratis VIRYA-ontwerpen.
Some recent new reports about small PM-generators have been added to chapter 6 of KD 341. A new chapter 7 has been added to KD 341. In this chapter, the magnet costs of the 26-pole radial flux generator as described in report KD 632 are compared to the magnet costs of the 8-pole axial flux generator as described in report KD 631. In chapter 7 also a simple methode is given to compare the maximum torque levels of both generators.
Reports KD 631 and KD 632 have been added to the list of free public KD-reports. KD 631 describes the 8-pole axial flux generator of the VIRYA-1.81. This generator has eight round neodymium magnets with a diameter of 45 mm and a thickness of 15 mm. It has a synthetic stator sheet which prevents the generation of eddy currents. KD 632 describes a 26-pole PM-generator using the housing of a 4-pole, 3-phase, 0.75 kW asynchronous motor frame size 80 and 26 neodymium magnets size 40 * 7 * 3 mm.
A new chapter 9 has been added to report KD 626 about the axial flux generator of the VIRYA-1.25AF. In this chapter the following measurements and conclusions are given for a steel stator sheet with a thickness of 3 mm. The sticking torque isn’t fluctuating for low rotational speeds. The pulling force in between the armature sheet and the stator sheet is 70 N. The rise of the stator temperature is 6 degrees C after running for 10 minutes at a rotational speed of 735 rpm. The power loss due to eddy currents in the stator sheet is only 8 W at the maximum loaded rotational speed of 650 rpm. The unloaded AC voltage for one coil with a test winding of 110 turns is 1.32 V for a rotational speed of 250 rpm, so the coils of the VIRYA-1 can also be used for the VIRYA-1.25AF.
Report KD 340: Rectification of 3-phase VIRYA windmill generators is reviewed. The curves which give the current I as a fuction of the phase angel have been modified such that the DC current for delta rectification is now lying a factor square root of 3 higher than the curve for star rectification. It was just the opposite and although the curves are relative, this might be confusing.