Low RPM Generator

Do you mean a car alternator? If so, and as it sounds like you want 120 volt ac, why not take power from the alternator stator 3-ph output (before the rectifier) and then use a transformer up to 120 volt? More efficient than rectifier (in the alternator) + inverter/transformer. You'd need to keep at least part of the rectifier for the alternator field supply, and the voltage regulator. Also don't know how low is low rpm, but car alternator won't put out a lot at much below 1000 rpm.

Cheers......Codey

No codey, here is the link.

http://www.otherpower.com/wardalt.html

This is what I want to feed the 12vdc in to 120 vac out, inverter with.

Thank you.

Just use the diode block of a 80 - 100 Amp truck alternator. these things are already 3 phase to begin with before the rectification stage. Regulation is going to be more of a challenge. I saw the 15 sec clip but it really didn't show anything. Consider using a diverter load to dump excess voltage into. Half to one volt to much will gassify your battery electrolyte beyond recovery. One volt to litte and your battery will never charge.

PM generators have been an engineering challenge for decades.

My friend built one almost 20 years ago. Never got it into production. Seveal prototypes flew apart from centrifugal forces.

He later determined a copper reluctor plate would be the best way to regulate the PM generator.

Ossapower from Glacier Bay CA has in production a 25kW PM genset. They are not very forth coming abou ttechnical details regarding design.

Elnav

http://en.wikipedia.org/wiki/Diode_bridge

found this here

If I'm guessing correctly, your generator will output 3 phases and then you'll rectify and regulate each phase at 12VDC?

Your generator will output AC straight from the coils which could be transformed to higher voltage. However if you are rectifying and regulating all phases to 12VDC I would get diodes, SCRs, banks of diodes, or something similar that can handle upwards of 150-200A for use on each phase output. I think 6000W is probably peak and only good for short periods of time. Install the diodes to your regulator + to ensure each phase is protected against backfeeding each other and connect the outputs of the diodes to the inverter +. Then I would tie the - of the inverter to the - of your regulators as commons.

When u get this done are u gonna post some pics on the web?

Thank you all,

In just starting to build it,getting all the parts,tring to figure out the best material,and what type of "Hub" to build it on.The turbine part will not be a prolbem to make,or making the stator or the feild[with the magneits].Just will need help on the voltage after making,I know that it will have alot to do with how many windings in each coil.

After making it I will post pictures.

tks again'

Johnny

What you are building is an Axial Flux, Permanent Magnet Generator. It has nothing to do with an automotive alternator. The builders use the old disc brake from a Volvo as the rotor to which they mount the permanent magnets. Voltage on this type of generator is a function of the number of windings in the copper coils. The 3ph comes from the number of coils and wiring they together in alternating sequence 120 Deg. apart, ie three groups of three to give you a total of nine coils total. Total output is a function of magnet strength. They use what are call super magnets in this case which are rare earth neodymium. I have built a number of these over the last couple of years. You can buy pre made Chinese generators of this type if you want.

Ferrari Guy wrote:I have built a number of these over the last couple of years. You can buy pre made Chinese generators of this type if you want.

REPLY

how did you handle the regulation?

http://www.nrel.gov/docs/legosti/fy98/24996.pdf

Thanks for the NREL link. Some documents are very hard to find & I was happy to see such a nice link.

The unit indicated in the link has high voltage out put and did not really give any details how the MOSFETs could control the output. At a guess a voltage detection circuit could be designed to switch individual coils in & out of circuit it would give a rather noisy out put and would require a fair bit of design work.

The inverter is not very fussy about frequency but would not like the voltage to exceed max design very much.A 12volt inverter does not have so much latitude for varying voltage input and a wind generator would certainly be all over the place and an electronic control would have to work hard to compensate and presumably have a lower voltage cutout when it could not produce any useful power.

I still think feeding a battery bank via one large regulator is the best option.

garth.You sound right,the wind speed would create up and down voltages,.Another idea.could I take apart a car alt. and use the regulator .

So what I would be doing is from the home built alternator feed the [car] regulator,then feed a set of deep cycle battaries , then feed the 12vdc to 120ac inverter.I belive the car regular will also have the blocking diodes in it already.

But this way it is not grid connected at all.So if i ever wanted to tie this into the grid I couldn't because i think that it would DRAIN out all the storage battaries.

I could live with being not grid tied,because I was going to put in a switch and another breaker pannel and just feed 1 room at a time to see how it would work out.

Being tied to the grid,would give you the advantage of making the meter go backward.

Thank you.

Johnny

Ps.A bunch of nice guys here.

Your generator is not really producing that much power about 750Watt max and that is going to average out much lower, being tied into the mains would discharge your batteries if the generator stopped .Only way to utilise the variable output is to invest in the largest storage system you can afford so you have excess power available,but the cost of doing this is high.you will have to do your sums to see if it is justified ie cost profit time and life expectation of your equipment.

Now if you build a 500Amp generator it would be worthwhile fitting an automatic voltage detection system to switch your inverter into the mains to cut in when the generator was producing power this would have to be carefully calibrated to operate properly.

Unfortunately you are into a whole new design project which is easier said than done , I suggest you do some carefull project planning before you decide on a course of action.

Sorry should have mentioned a car alternator regulator would only be good for the rectification diodes it would not regulate the output of this style of generator.You need a specially designed regulator which would cut in when the battery voltage was below a set point and if the generator was producing voltage higher than this it would charge the batteries, also you would have to have some hysteresis built into it to stop it constantly switching on and off until your batteries attained there fully charged potential . This could be done with half wave rectification and SCR switching There are basic circuits floating around on the net do some googling.

I had a good look at the report from the link. The paper focusses on the permanent magnets and coil stator. Only one sentence refers to the regulator mechanism. Its a special solid state inverter/controller. These kind of system have proven problematic in the past. I see mention of open circuit voltages of 70 + and on load voltages reaching more than 24V volts but also going below 12V in light winds.

This is not suitable for directly connecting to a battery or even a car alternator regulator which requires a field coil to adjust the magnetic flux field in the generator.

Xantex who took over Trace, has a number of Grid Tie systems all of which deal with the problem of draining the battery bank if charging is light and regulating the charging of the battery bank.

They also have controllers intended to handle both solar panels and wind charger sources.

There are other companies on the market with similar products. I have to ask. Is this effort to design/build your own stemming from a desire to innovate the technology concept, or simply a desire to avoid paying retail prices for equipment already on the market with plenty of R&D expended to pefect the system and get rid of the gremlins.

Elnav

The easiest way to generate own power whether wind or water or engine driven is to utilise the srepper motor from Fisher & Paykel washing machines- they are abundant in tips in Australia & N.Z.(made in N.Z.)- they only last about 3 years in the wm, & the stepper driving electronics fail- nobody seems to be able to fix them- a good source of advice is The Back Shed(google it).

Johnny,

If you already have a 6000 watt inverter designed to work from a 12V battery system I would assume you expect the Permanent magnet generator to feed this battery bank.

Have you got a design (circuit schematic) for a regulator suitable for working with a PM generator and capable of handling the wide range input voltages you will see under varying wind speeds? The report in the URL link only deals with a proof of concept. It omits the entire isssue of how to regulate it.

Secondly, a 6000 watt inverter will have a measureable idling current . From everything I have read about this proposed unit, you are only going to get around 700 watts or so. Not exactly a good match with a 6000 wat inverter. You are going to see unacceptable losses in the system.

You will have to build a wind generator suitable for charging a 12V battery bank directly. Otherwise it will not be compatible with your inverter. If your inverter is a commercial design, then it wil have a high voltage alarm circuit set around 15V to protect itself and the battery from damage. If your wind generator output voltage exceeds 15V then the inverter will shut down as a protective measure. Did you take this into consideration in your planning?

elnav. I just checked the inverter I have ,its a coleman 2000 watt got it last year. Sorry.not 6000 watt

oh boy,more problems to over come.On the net,were they build these with a break rotor from cars and the Neodymium magnets, it sounds like they put out from about 12 vac and above.It depends on the feild,[how many windings each coil has.]Then they put in a diode block,then into the battaries.This is where the regulator comes in, inbetween the turbine and the battaries.At first I plan just to use 1 or 2 deep cycle,like for a boat with a small electric motor. If it works then I will get the large battary that they use in forklifts.

I guess if I have to I can buy a regulator from a Solar store on the web.

here is a link of what I plan to build http://www.otherpower.com/20page1.html

But my rotor with the magnets will be about 14 inches in dia. with 12 magnets and 9 coils.

Here is what it should look like but with 6 vanies.

http://www.pacwind.net/#sea

Thanks for all the help and info.and all the thoughts to keep in mind.

I always say,you have to know the end result before you build it.

TKS.

Johnny

Johnny (guest) wrote: On the net,were they build these with a break rotor from cars and the Neodymium magnets, it sounds like they put out from about 12 vac and above.It depends on the feild,[how many windings each coil has.]Then they put in a diode block,then into the battaries.This is where the regulator comes in<<< snip >>>

REPLY: Yeah they say the target is 33.6V at 60 RPM. I could not find any mention of what wind speed was required to produce that 60 RPM. 33.6V is neither here nor there as far as battery systems are concerned. Way too much for a 24V ( 12V X2 batteries in series) and not enough for a 36 or 48V sysem.

I used to build controls for a 12kW wind gen with a 37 foot diameter prop. Coarse regulation was accomplished by adjusting the tail fin to trim the prop into or out of the wind. At full gale force winds, the prop was pulled at right angles to the wind flow direction. At 60 MPH and above, a shaft brake was applied.

Fine adjustment of the output voltage was accomplished by adjusting the field current. This unit was of swiss design going back to the mid sixties and resembled a big automotive alternator more than anything else. For direct grid-tie we used a 5kW Gemini converter tied to the variable output and converted it to frequency and phase matched AC for feeding the grid or simply feeding the house power sysem. As I recall, the 5kW converter cost around a dollar per watt or $5,000.

Admittedly this was back in the seventies, before permanent magnets were widely available.

A few years ago, I designed an inverter system to replace a system that worked much like your proposed PM generator.

The input voltage and frequency varied all over the place. A custom designed converter took this input and regulated it to produce 60Hz 120V AC that was supposedly rock steady. That system was ripped out after 10 years in use, due to numerous bearing failures several electrical fires and generally being out of service for too long and happening too frequently. I mention these problems not to discourage you but to let you know what problems have gone before and which you will also have to contend with.

Your Coleman inverter sounds like a normal off-the-shelf 12V Dc to 120V Ac inverter of about 200W capacity. If it is similar to all the others on the market, it will cut off at a low 10.5 V or close to it; and also cut off at around 15.0V DC at the high end

In other words the inverter is only going to work within a very narrow band of supply voltage between 10.5V and 15.0V DC

You will have to devise some kind of regulation for your PM alternator generator to limit your voltage to stay within that band. Otherwise you will not have 120V AC coming out of the inverter.

There are any number of marine and RV wind generators on the market with outputs in the 400 - 700 Watt range. These units typically charge a 12V battery bank in boats or RVs staying put in one place for days or months on end. They may not be the latest and greatest in technology innovation but they have proven to be reliable on multi year service. A 700 watt wind gen delivers 50 amps charging power to a battery. Even at half speed/capacity this is 590 amp hours every 24 hours or as much as three times the energy most luxury yachts with two people on board use in a 24 hour period to run lights, freezers, water makers, plus home entertainemnt and cooking equiment. The systems I design for usually consume 250 - 300 amp hours per 24 hour period.

Unlike land based houses, mobile applications like boats and RV tend to calculate power in terms of so many amps over so many hours going into or being taken out of the battery.

Land based houses tend to calculate power in terms of watts delivered to house hold appliances for so many hours. After the math is done, it amounts to the same thing. Work done over time.

Before you spend a lot of time, materials, and dollars, better figure out exactly how the various pieces comprising the whole system is going to work together.

If you pump 16V into a 12V battery it's going to fry in short order. If you deliver less than 13.2V to the battery, it will never charge properly. You have a 1.5 v window of regulation for battery charging and a 4V window if you attempt to drive the inverter directly from the PM alternator without benefit of a battery. This latter approach is not recommended.

Elnav

Thanks elnav.Your right on ALL you said.Im thinking hook up on these lines.

wind turbine /regular [controler] /battary bank /dc to ac inverter /pannel box.

I guess what is important is the "DUMP" circuit.That has to be used.

Thanks alot,and it was nice reading all that you had said.

Johnny