visual effect of capacitors


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GWatPE

Senior Member

Joined: 01/09/2006
Location: Australia
Posts: 2127
Posted: 12:02pm 01 Sep 2008      

Hi Gizmo,

This has been only a prelim investigation. This is the only way possible to do realistic testing on a mill in operation, ie add caps to mill at bottom of the tower before rectification. There is probably an LwC interaction. An engineer may have an explanation. The LC combination appears to prevent current flow above a certain frequency. The current returned to the battery load increased and then decreased as the mill slowed down. Very strange to see the currrent increase as the rpm decreased. When the caps were removed at the high rpm, the mill loaded normally to the full amps, so the load was not a problem. The emf diminished above a certain rpm. The cap effectively loaded the coil to a point that the output emf was below the battery voltage. I cannot explain why the mill rpm increased. maybe the current developed an emf in the wiring and this effectively unloaded the mill, like placing resistance in the line.

I want to test this stator in delta again with caps. I am sure the pole twisting has changed the output waveform from a pure sine wave. This will probably mean independent rectification of each phase and a cap across the winding, effectively across the rectifier. This will have to be on the mill head. Luckily there is plenty of room inside the yaw box.

I will not be able to use the chinese mill controller to do this. I will have to use a normal diversion load controller as mill and battery protection.

I have a heap of 470uF 180WV electro caps that I will back to back configure to be non polarised, approx 235uF. I will make some quick connects with flex to the stator. Solder or blue point connections will have to wait. I have zero loss type connects that will save me a heap of time doing mods with the mill lowered.

I was unable to do much today. Rain, and strong winds not much fun with live windmill testing.

High pressure system will kill the wind for a while, so OK to leave as is for a while.

I am still in 2 minds re caps. I will need to talk to Dennis about a series 80 to rewire, to allow me to direct compare previous testing he has done. I have seen an increase in power with caps. The test rig had much shorter wiring runs. It may be that the wiring and component placement may be critical aspects of a successful use of capacitors on a windmill.

This is likely the tip of an iceburg, so I will press on.

Gordon.
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