Author Topic: 5 m diameter wind turbine with 34-pole PM-generator for water pumping  (Read 4367 times)

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Adriaan Kragten

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My new report KD 614 has been added to the list of free KD-reports on my website: www.kdwindturbines.nl. This report gives the design calculations for the rotor of the VIRYA-5 wind turbine with 5 m rotor diameter, two wooden blades with constant chord and blade angle and a design tip speed ratio of 7. The rotor is used in combination with a 34-pole PM-generator made from the housing of a 6-pole asynchronous motor frame size 132. The generator is coupled to the 3-phase, 1.1 kW asynchronous motor of a centrifugal pump. The 34-pole generator is described in chapter 7 of KD 614. This is a wind turbine with a so called electrical shaft which may be coupled to any load if it is provided with a 3-phase, 1.1 kW asynchronous motor.

It might also be possible to drive the 34-pole PM-generator by a slow running water turbine to create a small 3-phase grid if the rotational speed of the water turbine can be kept constant at 176.5 rpm. Report KD 614 only decribes the idea. I have no plans to build a prototype or to start commercial activities with this idea but everyone can use it.

Ungrounded Lightning Rod

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Re: 5 m diameter wind turbine with 34-pole PM-generator for water pumping
« Reply #1 on: August 03, 2016, 09:26:08 PM »
TSR of 7 strikes me as a bit dicey.  At 68 degees F that means, even fully loaded, the tips are supersonic in a wind over about 110 MPH.
« Last Edit: August 03, 2016, 10:03:34 PM by Ungrounded Lightning Rod »

Adriaan Kragten

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Re: 5 m diameter wind turbine with 34-pole PM-generator for water pumping
« Reply #2 on: August 04, 2016, 09:45:19 AM »
A design tip speed ratio of 7 means that the tip speed is seven times the undisturbed wind speed V if the rotor is loaded such that it turns at the optimum Cp. The VIRYA-5 windmill is equipped with the hinged side vane safety system which turns the rotor out of the wind at high wind speeds. So this limits the maximum tip speed and it will therefore never come in the region of the sound speed.

kitestrings

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Re: 5 m diameter wind turbine with 34-pole PM-generator for water pumping
« Reply #3 on: August 04, 2016, 11:55:21 AM »
Adriaan,

Do you have any photos of the turbines built from your designs?  It would be great to see some of them.  One I recall in your reports had a interesting pivoting-tail design that I'd like to see.  Regards, ~ks

Ungrounded Lightning Rod

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Re: 5 m diameter wind turbine with 34-pole PM-generator for water pumping
« Reply #4 on: August 04, 2016, 09:44:24 PM »
A design tip speed ratio of 7 means that the tip speed is seven times the undisturbed wind speed V if the rotor is loaded such that it turns at the optimum Cp. The VIRYA-5 windmill is equipped with the hinged side vane safety system which turns the rotor out of the wind at high wind speeds. So this limits the maximum tip speed and it will therefore never come in the region of the sound speed.

Understood.  That's what it's intended to do.

But there have been a lot of discussions here about circumstances where such systems didn't work fast enough in a gusty wind, or failed due to various factors (such as wind-seeking, vertical wind vector components on a slope, turbulence throwing a gust into the face of a fully-furled rotor, misadjusted furling, stuck bearings, bent vanes, etc. - not to mention the old standbys:  accidental load disconnection and/or runaway due to current limiting becoming a limit to spin-resisting torque.)  So I'd still worry.

joestue

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Re: 5 m diameter wind turbine with 34-pole PM-generator for water pumping
« Reply #5 on: August 05, 2016, 12:06:39 AM »
you can drop to a tsr of 4 to 5 if you switch to a 5 blade prop.

It has a lower efficiency because the prop exerts more torque on the wind, and because of that the rpm is less, and the gear box must be made larger, or the alternator larger. neither of which is cheap.

but an efficient 5 blade prop would have thinner blades as well, so it would make little difference.

if you want to make a turbine that can survive 110kph winds, hardly matters if it has one blade or 5.
My wife says I'm not just a different colored rubik's cube, i am a rubik's knot in a cage.

Adriaan Kragten

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Re: 5 m diameter wind turbine with 34-pole PM-generator for water pumping
« Reply #6 on: August 05, 2016, 03:50:21 AM »
I have tested the VIRYA-4.2 windmill for some years on the test site near my house in The Netherlands. This windmill has a 2-bladed wooden rotor with a design tip speed ratio of 8 and a rotor diameter of 4.2 m. It was equipped with the hinged side vane safety system like I use in all my VIRYA windmills and it worked nicely. I now have more than 30 years experience with this safety system. Technically it is very simple and the delta-V characteristic is almost ideal. You find a photo of this windmill on my website www.kdwindturbines.nl at the menu VIRYA-folders and chose the folder of the VIRYA-4.2. The hinged side vane safety system is described in general in free report KD 485 and in detail in free report KD 213. At the menu home there is a 14 minutes film (in Dutch) where I am interviewed near my windmills and there you see two smaller VIRYA-windmills turning which also have this safety system. The effect of turning the rotor out of the wind on the rotor characteristics is explained in chapter 7 of free report KD 35.

Adriaan Kragten

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Re: 5 m diameter wind turbine with 34-pole PM-generator for water pumping
« Reply #7 on: August 06, 2016, 04:10:59 AM »
Arguments for the choice of the number of blades B are given in chapter 4.3.2 and chapter 5.2 of my report KD 35. The higher the design tip speed ratio, the lower the number of blades has to be chosen. To my opinion, for a fast running rotor and a direct drive generator one has to make a choice in between two or three blades. Both options have certain advantages and disadvantages. I have chosen for two massive wooden blades for the VIRYA-5 rotor connected to each other by a flexible steel twisted strip. No welding is required as it would be the case for the spoke assembly of a 3-bladed rotor. The rotor has a constant chord of 240 mm and a Go 711 airfoil with a maximum thickness of about 34 mm. It has a constant blade angle of 6 degrees and so the blade isn't twisted. Manufacture of a blade is therefore rather easy.

If I would have chosen for three blades, the chord and thickness would be only 2/3 of the chord and thickness for a 2-bladed rotor of the same diameter and design tip speed ratio. So the chord would become 160 mm and the thickness would become 22.7 mm. The bending and torsion stiffness goes down with the power of four of the scale factor so it goes down with a factor 0.198. These blades will be much too weak and too flexible and will be very sensitive to flutter. Another disdadvantage of the smaller chord is that the Reynolds value for a certain wind speed goes down with a factor 2/3 and this results in increase of the airfoil drag coefficient. The slightly higher maximum theoretical Cp of a 3-bladed rotor above a 2-bladed rotor (see KD 35 figure 4.3) will be neutralised by the higher Cd/Cl value (see KD 35 figure 4.6 and 4.7). For a 3-bladed rotor with constant chord blades, one has to chose a lower design tip speed ratio in between 5 and 6. However, this would result in a too high design wind speed in combination with a 34-pole generator running at 50 Hz (see KD 614 figure 5).

The main disadvantage of a 2-bladed rotor is that the gyroscopic moment in the rotor shaft is fluctuating; it is maximal for the blades vertical and zero for the blades horizontal. The gyroscopic moment is proportional by the product of the angular velocity of the rotor, the angular velocity of the yaw movement and the moment of inertia of the rotor. The hinged side vane safety system has a large moment of inertia of the head and this limits the maximum yawing speed and so it limits the gyroscopic moment. The fluctuation of the gyroscopic moment is decreased if the blade connection of the blades to the hub is made flexible. This is the reason why the connecting strip is rather thin (10 mm).

gsw999

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Re: 5 m diameter wind turbine with 34-pole PM-generator for water pumping
« Reply #8 on: November 30, 2016, 05:50:42 PM »
Adriaan I am having a look at your website,very interesting, do you have a youtube account?

Thanks

Gavin
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Adriaan Kragten

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Re: 5 m diameter wind turbine with 34-pole PM-generator for water pumping
« Reply #9 on: December 05, 2016, 03:07:00 PM »
I have no website account on You Tube but there is a 14 minutes long film on You Tube where I am interviewed (in Dutch) about my windmills. You find this film if you type "kleine windmolens" in You Tube. The same film is also on my website at the menu home.

I am just back as PUM-specialist from Dar es Salaam in Tanzania where I have helped a local company for two weeks with their production of wind turbines. They have built six wind turbines (three times 3 m + three times 3.6 m) according to the book of Hugh Piggott but faced a lot of problems with the rotor blades, the generator, the head bearings, the tower and understanding of the drawings in the manual. Finally the windmills are functioning acceptable but the design is clearly not optimised for serial production in developing countries.


Adriaan Kragten

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Re: 5 m diameter wind turbine with 34-pole PM-generator for water pumping
« Reply #10 on: February 14, 2022, 03:18:13 AM »
A new chapter 12 has been added to report KD 614 about the VIRYA-5 wind turbine. The title of this chapter is: "Use of a generator of Hefei Top Grand type TGET450-5KW-300R for grid connection". This generator is the same as the generator which is used for the 3-bladed VIRYA-5B3 as described in report KD 710.