Several here as well as myself have been looking for a way to hook up low resistance heating elements, (for heating air or water) and not stall their generator in low winds, since the heat elements look mostly like a dead short.
Having not found anything, I decided to make such a controller that could allow the turbine to start up with no load, then once it is running, PWM the load onto the turbine using the turbines variable frequency.
So basically, for those that may not understand, no load at start up, then once running the load will start to be applied, the faster the turbine runs the more load will be put on the turbine until the turbine can handle full load, at which point it gets the full load from set rpm's and higher.
The rpm the load starts to be applied is adjustable with a potentiometer.
The controller is run from the turbine itself so no outside power source is needed. A must I think.
The controller also has an auxiliary voltage regulator, output adjustable up to 37v. (in my case to run 2 small computer fans 12v
on bottom of heater)
I also added a 20 LED bar graph on the right side of board which starts lighting from the bottom up with increasing RPM's.
I designed it in bar mode with flashing full scale but once board was made I decided to change it to dot mode to save
some power. (changes are easily made)
The controller can take an input voltage of up to 250vdc (max for regulator) Fet's can handle 600v and 20 amps each, I used 6
of them giving me a max of 120 amps (plenty overbuilt)
I used a NTE995 frequency to voltage converter, it sends variable voltage according to frequency (RPM's) of turbine to a PWM built using a LM339 which sends its output to a mosfet driver.
Most all components can be obtained through local electronics store's or ebay.
The hardest part I think was finding some type of regulator that would work from such a wide range of input voltage, the regulator does get pretty hot so a good sized heat sink is a must on the transistors (max temp on them is 302 degrees F or 150 degrees C) I checked the heat sink at 150 degrees F and not a big deal since I am using the heat anyhow.
If anyone has a better idea for a wide range voltage regulator feel free to speak up. Something from 30v to 200v at about 1.5A I think would be fine.
I bench tested this controller then hooked up to turbine, it has been in use for about a week and has held up through 50mph winds we had last Tuesday night. I thought I had a problem with it today but it was a human error problem, lol.
My turbine starts powering the controller at about 30 RPM's since I am wound for high voltage output. If someone wanted to use this design for lower voltage turbines they could either use an auxiliary power source or use a boost converter, I did what works for me and it may well work for many others but feel free to change it to suit your needs if you like.
I design pcb's with ExpressPCB a free download, and have the file for anyone that wants it, it shows all the part numbers and part values, ex. resistors, caps etc...
If I have any problems or design updates I will post them and if anyone else has any ideas feel free to chip in.
There is no schematic, I design from data sheets and prototype boards, a schematic could be drawn up but I prefer not to, it would be pencil and paper if I did. I think its pretty simple though some of you may think otherwise by looking at the finished board, it does look busy but its not bad. One could even eliminate over half of the board space if ya threw out the bar graph display and the aux regulator.
Heres some pics, criticism and comments welcome.