Hello, i am in the process of building a small wind turbine using an 240/415v induction motor to grid tie. I understand i can grid tie phase to neutral and polyphase the other 2, what i am pondering is using 2 phases with a power resistor in series to drop the excess voltage, this would then enable me to switch the windings to delta (with also a series power resistor) at higher wind speeds. Can anybody advise if this would become problematic.
many thanks

 

First, using a power resistor to drop the voltage is not a good idea. If the power output was 1000 watts, and you dropped the voltage in half, then the resistor would be disipating 500 watts, think 500 watt light bulb. Which would be a tremendous waste. Using a properly sized transformer would be much better.
Second, you cannot simply tie a wind driven generator directly to the power grid. If the generator is not running at exactly 60hertz, then things will explode. It should be ran through a properly size converter which can make sure the power is running at 60 hertz and that the power is running from the generator and not the power grid trying to turn the generator as if it were a motor. This is not a easy or cheap thing to do.

 

First, using a power resistor to drop the voltage is not a good idea. If the power output was 1000 watts, and you dropped the voltage in half, then the resistor would be disipating 500 watts, think 500 watt light bulb. Which would be a tremendous waste. Using a properly sized transformer would be much better.
Second, you cannot simply tie a wind driven generator directly to the power grid. If the generator is not running at exactly 60hertz, then things will explode. It should be ran through a properly size converter which can make sure the power is running at 60 hertz and that the power is running from the generator and not the power grid trying to turn the generator as if it were a motor. This is not a easy or cheap thing to do.

The power dissipated by the power resistor would be low and used for water heating.
You can simply grid tie a wind driven asynchronous generator to the grid by rotating it faster than its given nameplate rpm, its how all the big turbines work

 

A sheepdog noted, an overdriven induction motor will act as a generator with the output voltage synchronized to the line voltage. You just need some sort of cutout to disconnect the motor when there isn't enough wind to overdrive it, otherwise it will start drawing power from the line, acting as a motor to drive the turbine.