Windturbine Alternator Vibration in Absorb & Float

[Halfcrazy]

Yeah unfortunately the PWM doesn't vary to infinite. (I can not remember why, boB said he couldn't do it that way) So the vibration (I liking to the sound of metal in a blender) is usually a sign of to low a resistance. Now that said anytime you PWM a turbine it is going to have some noise.

Maybe a short video of the noise?

[Boondocker]

The video does not capture the vibration with sound to well.  When the vibration starts it will cause tower rigging to rattle.   The dinging sound is the anemometer cable slapping against the tower.   The knocking sound is when the AUX2 kicks on and off completely.  When the wind is strong enough to keep AUX2 on,  the vibration will persist.

I'll take a video with the turbine pulling a good load without AUX2 activated for a comparison.    The turbine runs smoothly with the alternator making a "Geeeering" sound as it produces power.   

https://www.youtube.com/watch?v=OQIrdcfROeo

https://www.youtube.com/watch?v=And-3D4gaak

Boondocker

[Halfcrazy]

Yeah I would try higher resistance. You can play around with the resistors out of the clipper to make it easier. Not sure if 4 ohms will be to much?

[Boondocker]

Lowered the tower today to check the turbine out.   Did find the set screw on the blade hub keyway was loose.   This was a source of play and between the blade hub and alternator shaft.  Replaced the set screw with a bolt, jam nut and lockwasher.

Upon raising the tower, the vibration was less harsh when the Clipper is operating. 

Next, made various adjustment to AUX2 settings. Discovered that the AUX2  voltage setting can be negative.  In the light winds of today,  lowering the AUX2 voltage down to -2.0  made the vibration smoother.

https://www.youtube.com/watch?v=GvJcVf5grDY

The low grumbling noise in the video, is the sound made when the Clipper is active.

It is possible to replace one of the 0.8 ohm resistors with a 2.0 ohm resistors on each of the Clipper phases;  changing the total resistance to 2.8,  instead of 4.0 by relacing both?

Thank you for everyones help and input.

Boondocker

[Halfcrazy]

Yes if you put a 2 ohm and 0.8 ohm in series you get 2.8 that may be perfect.

Ryan

[Halfcrazy]

It is hard to tell in the video but that sounds pretty good. It will make some noise especially in lower winds. If you decide to try the 2.8 ohms just be careful that the turbine doesnt go over voltage on you

Ryan

[Boondocker]

Photo attached

[mike90045]

Photo attached

Ah, a cliff dweller.  Bet that one guy wire takes a heck of a load 

[Boondocker]

Mike,

Not that close to the cliff's edge.

The top guide wire  strength is 5X  above breaking tensile with 100 mph full face on the turbine rotor.  Also at that wind speed, the base of the tower column strength is 7X away from the buckle point.  I have the furling set so it begins to fold at 15 mph and the tail is completely collapses at 20 mph.   

[Boondocker]

I was able to make more improvements in reducing the vibration occurring when "clipping" by changing the wind curve. The new curve lowers the blade TSR.   Originally, I was allowing the turbine speedup, keeping the blades far away from stalling. Estimate TSR running in the 7 to 8 range.  I've since concluded while using the Clipper, allowing the blades to spool-up higher than optimum design TSR is not the best thing to do.

I'm thinking when the Clipper is activated, it slows the blades and decreasing the TSR. The blades  pull harder momentarily as the TSR passes down thru the optimum blade efficiency of TSR 6.  This causes the Clipper  to engage even more to counter act the increase in power created by the higher blade efficiency.

Now when the Clipper is activated there is still some vibration. The vibration is a softer purring sound. 

Boondocker