Help needed for PWM windmill controller

shortbus

Joined Sep 30, 2009
10,045
I guess I'm really dumb. To me, you shouldn't care about RPM of the turbine. At a certain output voltage the heater should start to turn on. Now I know that it takes a certain blade RPM to make that voltage, but some how you need to figure out what that RPM is. But that RPM is just a number, the voltage is the important thing. Once the voltage reaches your high limit you need a way to slow down or brake the turbine to lower the speed of the blades.

A window comparator circuit will do this for you. Under the low limit and no voltage would go to your heater, the blades would turn with no load. In the "window" (between low and high limits) the heater gets power. Once it goes into the high limit, the heater power shuts down and the gen stator coils are short circuited to each other to put the brakes on the turbine.

All of this done with out knowing any RPMs. Just the safe voltages for certain fan speeds.
 

Thread Starter

jbrols

Joined Jul 29, 2011
18
No you're not dumb :). Everything you wrote makes sense. That way of controlling would be almost the same thing as it was until now, when I was using just mechanical relays to switch the load on at a certain voltage.
But the thing is that it has to be at least three stage switching, it can not just connect a 3kW (at eg. 230V) load at one time, because at lower wind speeds it would act like a short and stall the turbine. Second issue is that this kind of switching creates a rapid braking of the turbine, which too isn't good. I guess, I already have decreased "health" level of my generator by doing that kind of switching and braking.
The PWM controller, I hope, should let me connect just one 3kW load from the start of voltage rise and use it at heavy wind gusts too.
You are right, I don't really care about the RPM of turbine, as long as it doesn't run without a suited load at high winds.
I'll just have to try this controller and see, what it actually will do.
 

Thread Starter

jbrols

Joined Jul 29, 2011
18
Managed to draw a complete schematic for this PWM controller with some modifications:
1. Using LM393N instead of LM339.
Can I do so?
2. Using phase voltage instead of line voltage for 15V linear regulator to reduce voltage drop across transistors.
Will it work in this situation, if both rectifiers have common ground, or should I use separate grounding for power mosfets+heater and another for all the rest circuitry (picture 2)? Can there appear some sort of "conflicts" between these two?
3. Is there all correct in a LM317 voltage regulator part? Why are there these 680 Ohm resistors at the output as from the original PCB drawing?

Please, take a look and criticize, if needed. If it's OK, I'll have to redraw the PCB.

P.S. Finally found out, how to attach pictures correctly :D.
 

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Dodgydave

Joined Jun 22, 2012
11,285
Your 680ohms resistors need to go across pin 1 and pin2 of the LM317 to make it adjustable. It looks like its using the ac signal as the speed source to convert it to a dc voltage using the lm2917, then using an lm393 as a comparator to switch on the heater. The pwm is altered by C12/ R6 combination, also Vr32 on pin 3 lm393.
 
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Thread Starter

jbrols

Joined Jul 29, 2011
18
It looks like its using the ac signal as the speed source to convert it to a dc voltage using the lm2917, then using an lm393 as a comparator to switch on the heater
- that is clear even to me :)

I asked about the LM317 configuration, because it seemed strange for me too, but in the schematic I drew it the way it was in original PCB (pic. 1). So there is an error in the PCB.

But what about my idea of using these two separate rectifiers? Can it be done that way without burning anything? Can't figure it out, until no smoke has come out :confused:

Two versions of possible schematics- which one would make sense?

I really appreciate your helping to the dumbest part of population :D
 

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Dodgydave

Joined Jun 22, 2012
11,285
No probs it s not a dumb question, i would use the first drawing and connect all the grounds together.


PS just what are you trying to achieve from this, hotter or colder heater temp?
 
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