Low Speed VAWT - Turbine Startup

Mohamed AbouElNaga

Hi,

We are building a low vertical axis wind turbine and we are actually facing a problem which is the high cogging torque in the ac generator which prevent the generator from being a self starter. we are a thinking for a solution for that issue so we thought why wouldn't we drive the generator with an ac voltage coming from an inverter which is driven by the batteries, but actually we are not sure about that solution. Briefly, we have a controller that have some feedback such as RPM, wind speed, voltage, current measurements so I think we can use those variables in order to control whether or not to feed the generator from the inverter through some sort of controllable switching so would anyone please advise us if that is possible or not and if its possible how could we calculate the amount of power needed to overcome that cogging torque and start the generator as a motor.

attached is a simple block diagram describing the system and explaining the concept that we are worried about.

Thanks
Attachment not found.

BB.

Here are some examples on how to decogg an alternator:

http://www.thebackshed.com/Windmill/articles/decoggingFP.asp

Here is an example of a wind turbine made from a pair of brake rotors that has little cogging.

http://www.otherpower.com/davesmill.html

The last thing possible. Alternator are actually three phase motors. You could connect up a vfd to start/drive the alternator (use an external anamometer to measure wind) and then switch over to the rectifier--And technically, there is a good possibility that the VFD can be "driven backwards"--Basically become a synchronous rectifier (if you have DC input to the VFD).

Depends on your hardware and the amount of controller electronics and programability, there are some interesting things possible.

-Bill

waynefromnscanada

Also something else to consider - - if the wind speed is not high enough to start the alternator, is it really high enough to produce any useful power anyway, or would it just be wearing out the bearings to provide something interesting to look at?