Hi guys, am after a little - or a lot of - help...
Have found myself quite stuck with a project currently. Wind turbine (VAWT), using an old washing machine motor as a generator. Produces an output up to 300V 3phase AC, 2-3A unloaded, when used as a gen.
The ultimate goal is to build a circuit that will output either 12 or 24V constant from this turbine. Problem is, how do I do that when (depending on wind speed) the voltage generated is going to vary dramatically anyway.
Rectification of 3ph AC to DC is fine, I can deal with that, it's the regulation that's killing me. I've been told, and from the limited knowledge I've got it seems logical, that a PWM circuit for regulation is the way to go. If so, how do I go about building one? If not, then is there a better option over PWM?
I'm quite stumped and any help would be greatly appreciated. I've been a muppet and left it until the last minute, only a few weeks until the final product is due.
Help!

 

If you are going to draw 2-3 amps then a linear voltage regulator will be fine. Of course, PWM is more efficient but a linear voltage regulator is easier build because you buy a ready chip and a few capacitors. Search in google for 5 amps voltage regulator or visit www.national.com to find one.

 

I had considered the linear regulator, although I've been advised that a linear regulator will not be enough to count as my project, apparently not enouogh work involved. Hence the need for PWM, apparently that's "enough work" to pass for this project... Unfortunately.

 

Some points to think about.

I presume this is an industrial washing machine moter if it produces 3 phase. To output 300 volts it must be spinning at a fair old lick (spin cycle?). Even an industrial machine will not last long run continuously at this speed.

Wind speed varies considerably. Thus spin speed and thus output voltage also varies considerably.

In this situation the aim of the game is to store the energy produced and then represent or reconstitute it in some more consistent form. This is not to regulate it, for a regulator will simply throw away the difference between your 24 volt ouput and the 300 volts plu input.

If you were to operate a scheme whereby the energy was stored in a capacitor and then drained off to use through, say a pwm invertor, you would encounter problems because of the range of voltages generated. When the moter ouput was low the capacitor would discharge through it, rather than the other way around.

So ypou will be looking to store the energy inductively (in a magnetic field) and transfer it that way.

Your first and most important step is to determine (measure) the range of voltage output from the turbine.

 

Here is an outline scheme for you to talk over with your project supervisor. Remember these voltages can very quickly destroy components, and even kill humans.

The variable AC input from the turbine is rectified by rectifier R.
This rectified voltage charges capacitor C to say 30 volts.
When the control amplifier senses that the capacitor has reached say 35 volts it opens (electronic) switch SW, disconnecting the supply from the turbine.

All the time the load L draws current through the regulator R from the capacitor, reducing the voltage on the capacitor.

When the capacitor voltage has fallen to say 25 volts amplifier A recloses the switch and allows more juice into the capacitor from the turbine.

This cycle is happy so long as there is a load drawing current.

 

Hey cheesy,
When you reach cut-in speed, you usually regulate the voltage to produce more current to charge a battery bank, then take the constant power off the bank. Excess goes to a heater or light load. Try otherpower.com. I'd like to know why a PWM would be used, if your output is DC, unless you are running a motor, which would be a waste of power. Always willing to learn.
Dan