PWM Heating load controller based on frequency

[methanolcat]

zvizdic,

     Don't worry about the transformer, were not going to need it for the lower voltage circuit, I only used it to drop my incoming voltage to something more reasonable, I didn't pull any noticeable current from it anyhow, its only there to give a zero crossing signal to the frequency-to-voltage converter chip. The chip has a max input voltage of like 28 volts, I think. In your case we will just use a simple zener clipper to keep the signal to a respectable level, since we need almost no current I think this will be a good place to use a zener clipper.


       Most likely winter heat, more, more, more, and I have a couple other things up my sleeve as well, never buy a grid tie inverter though, it would just cost way too much for those kind of power levels.  Yes it will be a huge undertaking.  The old tower (experimental tower and trubine) was made using 2" angle 1/8" thick for the legs and 1/2" round bar cross braces, 40 feet tall at the platform, 50 feet at the center of the blade hub. The new tower, legs will be 4" square tubing 3/16" thick and cross braces will either be angle iron or 1" square tubing. also 40 feet tall at the platform, 55-58 feet at the center of the blade hub, depending on blade diameter.

      Probably go with wood blades again, mine have held up great and at scary fast speeds (too fast actually), a jacobs type hub will be used to keep the rpm's down on the bigger one I make.

      I will start a new post once I get something going and take pictures to post.

    Matt

[methanolcat]

zvizdic,

         read your mail, sent you a message.

[zvizdic]

Hi Matt

What is your motor rated as a original tag was shoving?
You maintained  gearing up and using a bigger blades, just wondering if you considered case strength and bearings with bigger load.

Darko

[methanolcat]

zvizdic,


      The motor I used was a 7.5 hp baldor motor with a steel case and iron end caps, the bearings and case are plenty strong enough. One thing that helps motor conversions when it comes to the bearings is that the bearings are set a large distance apart, with the very large front bearing carrying the majority of the load, much as it would if used as a motor with double or even triple pulley and belts.

      These large motors are designed very robust in the first place. My conversion thread with pic's. http://fieldlines.com/board/index.php?PHPSESSID=97e89149bb8c1782a5b6894325d6c8b3&topic=138101.0
 
      I have not used a gear box yet, I am swinging my 15 foot prop directly on the 1.5 inch output shaft of the motor conversion with no problems.

      I'm not sure I'm gonna gear up the small 7.5hp motor conversion, if I'm gonna be making 10, 15 or even 20kw I don't think this small motor conversion is what I want to be using. I have 60 more magnets and several candidates for converting the smallest being a 25hp motor.


        Matt

[zvizdic]

Matt

I would tray to use that motor first(nothing to louse)of course if you used H class magnet wire.
Since you think it is plenty overbuild it should be safe to 10KW maybe 15KW.

Your progress is going to capture many observers ,cant wait.

If you need something like this you are welcome .

[ghurd]

and several candidates for converting the smallest being a 25hp motor.

Go with something larger.   
25hp conversion would hardly power a small town.   

I agree with zvizdic, "Your progress is going to capture many observers ,cant wait."

That takes spheres composed of a copper and zinc alloy.
G-

[Volvo farmer]

If you need something like this you are welcome .

What is that?

[TomW]

If you need something like this you are welcome .om

What is that?

I have $3 that says it is a large size bridge rectifier of the 3 phase type.

Tom

[zvizdic]

At my work I build moulds (with everting else) for insulators that are used for  commercial windmils.
My gees is a insulator for oil cooled transformer.
I keep some samples, maybe I need them sametime .

Like this

[Janne]

Hi Matt,

I was wondering, since you're feeding the raw PWM waveform to the heating elements, has this been causing any noise problems. I've been planning to start working on a new attempt with the heating PWM controler, and was wondering if you have had any electrical or audible noise problems with the raw PWM wavefrom being fed to the resistors?
In my first attempt, I had a damping choke to limit the slope on the PWM, but I'm wondering if it's possible to get away without such extra parts .

[methanolcat]

Hey Janne,

       I'm switching at 18Khz which is near the top of the audible range for human hearing, 20Khz being the top. A teenager might be able to hear it but I sure can't, my hearing isn't so good anymore since I have always worked around machinery without protection. My wife has pretty good hearing, although she doesn't hear me most of the time.....hmmm, and she hasn't heard any noise from it.

      We have had younger family visit and they have not said they could hear anything so I don't think its a problem, if it was you could always bump up the pwm frequency to just over 20Khz and I don't think there would be any problem with it either.

      High frequency isn't a problem as long as you can turn the switches on and off very fast and for that I use mosfet drivers, cheap solution and thats what they are designed for. I use TC4422 9amp drivers in most switching projects, $5 and no problems, overkill for this as they have lower amp rated drivers as well but the cost is about the same. I have driven 22 mosfets in parallel with a single driver without any problems.
 
      I do use the 5 pin to-220's so I can easily put a heat sink on the driver but they do have 8 pin dip's as well, they are harder to heat sink and their ratings are lower but I think would most likely be fine for 4 or 5 mosfets in parallel.


           Matt

[methanolcat]

zvizdic,

        Thanks for your offer on what looks like a 3 phase bridge but I think I have all I need. I use the big stud mount diodes on an aluminum heat sink. Thanks anyways.

        Matt