Homebrewed Electricity > Wind

Help needed on a Breezy type grid tied induction turbine

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joestue:
no you need a transformer or variac.

you can use any transformer to reduce the voltage by its nominal voltage. so the cheaper modified sine wave UPS usually have a 16 volt center tapped transformer in them. the pure sine wave units that use a 24v battery usually have a 13 volt transformer in them.

two of those 16 volt transformers can be configured to reduce your 120v line voltage by 8,16,24,32 volts and they are usually good to around 20 amps. a reduction of 32 volts is about 25% reduction and that may be enough to reduce the no load power draw by half.

anyhow if you reduce the voltage to reduce the cut in, you're going to get more power out of the turbine. however once you start seeing real power from that motor you need to increase the voltage, and once you get to around 600 watts power output, any reduction in voltage will decrease efficiency and the motor will be operating at higher temperatures. basically there is an ideal voltage for the power output.

Kyle:
I like the idea of the variac, less complicated.

What about changing my blades angle from 5 degrees to 3 degrees and making them longer? Wouldn't that catch more wind and cause them to turn with less effort?

joestue:

--- Quote from: Kyle on February 06, 2018, 11:53:09 AM ---I like the idea of the variac, less complicated.

What about changing my blades angle from 5 degrees to 3 degrees and making them longer? Wouldn't that catch more wind and cause them to turn with less effort?

--- End quote ---
changing the blades changes everything, too many variables. increasing the diameter reduces the rpm for the same windspeed, but changing the angle will compensate for that a little bit.

and what does "turn with less effort" mean to you? torque produced by the blade increases with the diameter cubed for the same blade angle and geometry. the rpm drops linearly with diameter, so power produced follows the square of the diameter, which means you need a higher gear box ratio. this doesn't solve the fundamental problems associated with direct driven induction motors.. which in your case is the low efficiency of a single phase 750 watt motor.

don't most direct grid tie induction motor generators have variable pitch turbine blades? yours seems to be working only across a relatively narrow range of wind speed.

Kyle:
I don't have the capability to make variable pitch blades.

"Turn with less effort"- I guess a low tech way of saying the blades will apply more torque to the motor.

I understand the inherent efficiency limitations of my 750 watt motor. I was just hoping/trying to maximize what is there. I appreciate all your suggestions and information.

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