Wind Generator - Star Delta Controller

[Nigel Goodwin]

The field current doesn't take much power and it's required anyway providing it doesn't have a permanent magnet rotor. Therefore it makes a lot of sense to reduce it at high speeds so the voltage doesn't exceed the battery's maximum and increasing it at lower speeds will make the alternator more efficient since it will be producing power that would otherwise be wasted.

I would disagree, the field current takes a fair amount of power - which you can't afford to waste in something like this - any power going to the field coil isn't going in to the battery!. Using a permanent magnet means you get maximum power all the time - when the battery is fully charged you dump the excess to a dummy load. This may sound wasteful, but it's no different to the field coil - where you're still wasting wind energy once it's fully charged.

 

[Hero999]

Why is it that they use field wound machine in cars then?

To get an output at different speeds; isn't that what we want?

Also note that I'm saying you should keep the field carrying current continuously (like I said before) there come a point when it isn't profitable to keep it powered and there should be a switch to disable it.

 

[HarveyH42]

Why is it that they use field wound machine in cars then?

To get an output at different speeds; isn't that what we want?

Also note that I'm saying you should keep the field carrying current continuously (like I said before) there come a point when it isn't profitable to keep it powered and there should be a switch to disable it.

In a car, the alternator is spinning fast enough to be self powered when the engine is idling. Once the car is started, you don't even need the battery.

The wind doesn't blow constantly or consistantly, so you need to store what you can. Field windings instead of permanent magnets would use power, and you would have to wait and measure RPMs until the speed came up enough to produce more energy then the field would consume. So, yes the magnets put drag on the rotor, but that's another design issue.

My wind power experience has gotten past stepper motors and LEDs (no batteries yet). Tomorrow should be our first tropical storm through central Florida, so get to see some bright flashing lights, or maybe searching the yard for pieces...

 

[williB]

There is no field winding on a F&P alt/motor.
it is a permenent magnet three phase motor ,which makes it a very nice three phase windturbine alternator

 

[Pommie]

Wouldn't the most efficient system be a star configuration with a SMPS to convert to 12V. The diode losses at high voltage/low current are reduced considerably and SMPS are very efficient.

Mike.

 

[Nigel Goodwin]

Why is it that they use field wound machine in cars then?

Because you have energy to burn, and it's a VERY easy and effectvie way to control the amount of energy output.

To get an output at different speeds; isn't that what we want?

No, we're wanting the MAXIMUM possible energy from the wind.

Also note that I'm saying you should keep the field carrying current continuously (like I said before) there come a point when it isn't profitable to keep it powered and there should be a switch to disable it.

????? - no field current, no output (well hardly any), what good is that?. And on the other hand, you need maximum field current when the alternator is spinning slowly - energy you can't afford - particularly when it gives no advantages for a wind generator.

 

[HarveyH42]

Well, the savonius didn't make it through the night, top section came off. Will re-glue it when it dries off. The propeller version is still going strong. Funny thing, the storm we had last night wasn't Tropical Storm Barry, late this afternoon I'm guessing.

 

[simoin]

okay so I have my 3 phase Permanent Magnet generator, now how do I switch from star to delta when the wind kicks right up?

Pommie - stupid question for you, what do SMPS do? I was just going to rectify it to 12volt using 50Amp car rectifiers. I have a diagram for there hookup at home somewhere.

Sorry to hear your savonius did not last through the start of the storm.

I have also talked to Ed from: www.windstuffnow.com/main - who says:

The controller I used was from design specialists as you posted on the alternative energy site. I don't believe he is building them or any other kits right now. Really to bad for us, they worked great as well did his tack jr. I don't know of any thing out their comparable to it.

--

So this means no one has a product like this and for some rising entrepunear that there would be a market for a product out there... I think we have also established that a field current generator thing is not going to happen as this is a PMG device...

 

[HarveyH42]

The savonius rotor was more of a toy, first one I threw together to see how steady and how big (wasn't big enough). Will give it another try sometime.

Switching the winding configuration doesn't seem that bad. Might be able to measure the output voltage, and switch when it's much higher then what is needed to charge the battery. Just need to determine at what point you will still get more then 12 volts, when you go to the higher current configuration.

 

[JTECH]

Look at how an automovtive regulator works.

It adjusts the DC rotor current to keep the output voltage the same at different engine speeds. At high speeds the rotor current is reduced lower speeds the current is increased.

Switching from star to delta can be useful for varying the voltage but it isn't as effective as varying the rotor field current.

Hi folks! As far as I can understand about wind turbines/generators, is that usually the field cannot be adjusted electrically, because it consists of permanent magnets. One should look at a mechanical means of adjusting the air gap between the magnets and the stator, i.e. reducing the gap proportionally as the speed increases in order to get the most out of the available wind. At low speeds, a bigger air gap means less "cogging" and the machine can speed up easier. Come on, let's hear from the mechanical-inclined people on this forum!
Regards all.

 

[Hero999]

That's a good idea!

A centrifugal governer system could be used to pull the magnets out of the coils as it spins faster.

 

[simoin]

I want a star/delta controller

okay so these are all great idea's but the original questions remains, does anyone know how to setup a star/delta controller that is user adjustable so that the optimum change over point can be found after achieving and holding optimum point for x seconds?

see the picture below for what the magnet block looks like.

**broken link removed**

Please have a browse around of this website to see exactly what it i am doing... www.thebackshed.com

Thanks for the help thus far

 

[Nigel Goodwin]

okay so these are all great idea's but the original questions remains, does anyone know how to setup a star/delta controller that is user adjustable so that the optimum change over point can be found after achieving and holding optimum point for x seconds?

It's easy to do, either using a micro-controller or just opamps etc. Simply measure the speed of the rotation, if it's below a certain level then select it as a high voltage connection, if it's above a certain level then select it as high current. Without a micro a simple frequency to voltage conveter feeding a comparator should be all you need?.

 

[simoin]

so is the sort of op-amp you are referring too? https://en.wikipedia.org/wiki/Operational_amplifier

How would you suggest measuring the speed of shaft rotation?

 

[Nigel Goodwin]

so is the sort of op-amp you are referring too? https://en.wikipedia.org/wiki/Operational_amplifier

Yes, used as a comparator, or you could use a specific comparator chip?.

How would you suggest measuring the speed of shaft rotation?

There's a frequency to voltage IC you can get (I can't remember the number off hand, but someone will probably post it shortly?) - or you can use a 555 in monostable mode.

 

[rippersoftware]

Tachometer circuit

so is the sort of op-amp you are referring too? https://en.wikipedia.org/wiki/Operational_amplifier

How would you suggest measuring the speed of shaft rotation?

Scoraig measures based on the rise of voltage from the AC generated from the 3 phases. Captures this and runs it thru a tachometer circuit.

From there, you can do what you want with the analog information. Scoraig switches heaters onto the output for load based on RPM. See the page:

https://www.scoraigwind.com/circuits/index.htm

RipperSoftware

 

[Hero999]

Thank you and welcome to the forum.

 

[jolino]

Hi Simon,

Considering all what people said, let me suggest one more simple solution in contrast with the circuit that you have posted in first place, and again, considering some cited aspects.

1. The rotation sensing is maded by viewing the wave/signal present in any point of any coil, before rectifiers. No more hall-efect sensor needed.
To make this work, the generator/battery disconnection must be made beetwen the bridge and battery.

2. I suggest 2 relays intead of one by two reasons:
a) When STAR relay is OFF -> STAR position, no battery discharge.
b) When ON / OFF relay is OFF -> generator is desconnected from bat and no bat consumption.
- So, when both relays off, just a few miliamps from battery.

3. With the KEY, you can configure:
a) The speed at wich the system switch from star to delta.
b) The speed at wich the system disconnect the generator.
c) If needed, you can have generator disconections to max and min speed.

4. You have also STAR/DELTA indication througt the Leds.

Notes:
1. Of course you need a little 78L05(+5V) to supply the PIC.
2. The software to do it, is very easy.
3. Sorry for duplicated references in the schematic.

Regards
Jolino

 

[simoin]

anybody else have any thoughts on the new circuit jolino ha put forward, it sounds as if it will be great. I think i can work out a 5volt power supply for it easy enough too.

 

[Klaus]

Adjusting field current in a permagnet magnet rotor??

It appears that many respondends jumped on the bandwagon without bothering to read the links you posted, where it becomes obvious that there is NO field current to adjust with a permanent magnet rotor.
So you are right to ponder the star/delta question.
Nigel's reply gives you a good reason why bothering with that complication.
My practical suggestion is how to accomplish this:
Do the switching bit with a suitable relay.
Control the relay from a centrifugal switch.
You may salvage such a switch from any single pole squirrel cage AC motor, aka ex washing machine (not Fisher Paykel;-).
You may have to tinker with the centrifugal weigths to get the right switching time. To do this rig up the wind generator minus the blades and drive it from a suitable variable RPM source - if I had to do this I would use my lathe for the driving power.
The electronic 32 point switching module seems far too complicated for this application and I can't see why anybody would require so many switching points unless you plan to use variable geometry adjustable blades for your windmill.
Klaus