# Generator questions..any Tech guy's around.?



## metaltrades01 (Aug 24, 2012)

Hi there,
I'd like to use a Steam engine to drive an electric motor to generate power. 

Ideally I'd like 13/14v (to charge a battery) and 6 to 8 amps @ about 400 rpm. 

What I have learnt online, a permanent magnet electric motor is the way to go.


What size motor should I be looking for? one that has a bit higher amp output than this?

Is a 24 v motor too high?

and what about the motor rpm, what should I look for?

I'd happily rewind the armature if need be.

Any advise or a link to a website would be appreciated,

Thanks in advance,

Martin


----------



## albertorc19 (Aug 24, 2012)

Regarding your question about the 13/14 volts needed I think that 24V is not too high. The generator ouput should be alternating current power (VAC) therefore a diode in line will cut the peak voltage by a half but this is not very efficient since you'd be wasting half the power produced by the generator. You can turn this VAC into VDC using the proper circuitry which can include a 12VDC regulator, it is not 100% efficient but is far better than using a diode. In both cases you must be sure that the components can handle the required current.
The rpm is not big deal,if you can borrow an instrument to measure the frecuency of the VAC generated, some voltmeters have the "Hz" function. Once you know this you can do the math  to calculate the values of the components for the battery charging circuit. Please work safely, batteries have acids and other substances that can be harmful if overheating or other accident occurs.
This may be useful for you: http://www.leaverindustries.com.au/Little_Black_Book.pdf


----------



## MachineTom (Aug 24, 2012)

What you want to do is generate about 100 watts. A brush type motor with permanent magnets for the field will generate DC not AC voltage. You would need a cutout relay in the circuit, this relay would be set above battery voltage, and energized by the generator, when the output of the generator exceeded the setting of the relay, the relay would close and allow power to flow to the battery, if the voltage falls below the hold in voltage the relay opens there by disconnecting the battery from the circuit. This is to prevent the generator from becoming a motor and driving the steam engine. Diodes can be used to preform the function as well. 

For sizing a motor of 300+ watts should be capable of generating 100 watts.


----------



## metaltrades01 (Aug 25, 2012)

albertorc19 said:


> ..... it is not 100% efficient but is far better than using a diode. In both cases you must be sure that the components can handle the required current.
> The rpm is not big deal,if you can borrow an instrument to measure the frecuency of the VAC generated, some voltmeters have the "Hz" function. Once you know this you can do the math  to calculate the values of the components for the battery charging circuit. http://www.leaverindustries.com.au/Little_Black_Book.pdf



Thanks Albertorc19.. I'm a fitter/machinist & I don't know a lot about electricity..if you don't mind..a couple of questions...

From what your saying...do you have any idea how efficient it would be?

If the rpm of the motor is say 3000rpm, would it generate full current at 400rpm? or do I need to find a slow revving motor?..or what would be the ideal motor to find for what I want to do?

Is there somewhere on the net I can find the calc's?

Thanks for the tip about the lead acid battery's and link.

Thanks martin

...in due coarse, I'll post a thread on the steam engine and generator.


----------



## Dan Rowe (Aug 25, 2012)

Martin,
Some of the best places to look for information about DC motors as generators is on wind power sites. I kept an eye on ebay for a while until I found a cheep permanent magnet DC motor which was a tread mill take out.

Here is a link to a Baldor motor pdf that might help. It gives the calculations I think you are looking for.
http://www3.zetatalk.com/docs/Motor...As_Generators_In_Micro-Hydro_Systems_2000.pdf

Dan


----------



## kf2qd (Aug 25, 2012)

You want a motor with the lowest possible RPM at the rated voltage. What I mean - if you get a 24V 3000RPM motor it will put out 12V at approx 1500RPM depending on the load. It might actually put out a lower voltage. The faster the motor is rated , the faster it will have to run to put out any current. Your generator will need to run faster than engine RPM to produce useful current.

I have built some RC Brushless motors, in that field they use the term KV for thousands of RPM per volt. a high KV motor (high speed) will have to be run faster to generate and currnet, a lower KV motor will have to be driven at a slower speed to generate a usable current.


----------



## metaltrades01 (Aug 26, 2012)

MachineTom said:


> What you want to do is generate about 100 watts. A brush type motor with permanent magnets for the field will generate DC not AC voltage. You would need a cutout relay in the circuit, this relay would be set above battery voltage, and energized by the generator, when the output of the generator exceeded the setting of the relay, the relay would close and allow power to flow to the battery, if the voltage falls below the hold in voltage the relay opens there by disconnecting the battery from the circuit. This is to prevent the generator from becoming a motor and driving the steam engine. Diodes can be used to preform the function as well.
> 
> For sizing a motor of 300+ watts should be capable of generating 100 watts.



I'm low getting back to you Machine Tom... I might be wrong, are talking about a voltage regulator?


----------



## metaltrades01 (Aug 27, 2012)

Thanks for the advise above... I don't know anything when it comes to power generation.

To clarify a few things, the motor needs to be..
- rated at 3 times the power (watt's) I would like to generate.
- a permanent magnet motor is best.
- turned at the same "powered motor rpm" to get the same voltage.

and which is more efficient? 
1/ brush or brush less? ...which is probably a DC (brush motor) and AC (brush less motor)
2/Diodes or a voltage regulator?

Martin


----------



## albertorc19 (Aug 27, 2012)

I think that a DC motor is best suited for power generation in a small scale. I've seen great advice in this thread, the addition of a relay seems like a very wise thing to do. The relationship between rpm and voltage output makes perfect sense to me, it's Faraday's law in practice . A voltage regulator is better for VDC. Once you set up the steam engine at fixed rpm's the voltage should be a few volts higher than the desired voltage, this is the "in" voltage for the regulator, the voltage at the regulator output is the specified for it. A voltage regulator will compensate the variations of the supply to deliver a constant voltage.
VAC is more efficient than VDC for power transmission but this applies with really large amounts of electric power that must by carried long distances, that's why the electric grid is VAC. There was a huge argument when Mr. Edison said that VDC was the way to go and Mr. Tesla said that VAC was far better than VDC. Time, economics and sound science proved Mr. Tesla right.
I think I'll make my own small experiment these days with a small brushed DC motor, I'll turn it manually in order to see what can be seen in the oscilloscope and report my findings here.


----------



## Ed T (Aug 27, 2012)

You might also want to take a look at a small alternator like those found on small tractors. I have a KUBOTA lawn tractor and it has 10AMP 12v alternator that is about the size of a large tuna fish can. I don't know if the regulator and rectifier is internal or not, but it's a cute package. Alternators work better than generators at low RPM. WRT efficiency, the overall efficiency of your steam power plant will be lucky to get out of the single digits. Also, assuming you're not planning on high pressure steam, you're going to need a pretty big engine and boiler. Using the three to one ratio suggested above, it will need to be a 1.5 ish hp engine which is bigger than you might guess. Cut lots of sticks for the boiler. It will eat them fast.


----------



## metaltrades01 (Aug 27, 2012)

albertorc19 said:


> I think that a DC motor is best suited for power generation in a small scale. I've seen great advice in this thread, the addition of a relay seems like a very wise thing to do. The relationship between rpm and voltage output makes perfect sense to me, it's Faraday's law in practice . A voltage regulator is better for VDC. Once you set up the steam engine at fixed rpm's the voltage should be a few volts higher than the desired voltage, this is the "in" voltage for the regulator, the voltage at the regulator output is the specified for it. A voltage regulator will compensate the variations of the supply to deliver a constant voltage.
> 
> I think I'll make my own small experiment these days with a small brushed DC motor, I'll turn it manually in order to see what can be seen in the oscilloscope and report my findings here.



Thanks for the advise Albertorc19, I don't know a lot about electricity generation. I'll go with the regulator.
I'd be keen to see the results that you get.

Martin


----------



## MachineTom (Aug 27, 2012)

MT, What I was describing is a cutout relay, it only cuts the generator in and out of the circuit, The next step up from that is a regulator, which in the case of a permenent mag genertor dumps the overvoltage to a resistor.

A brushless type DC motor would work but you need some fancy electronics to make that happen, as well as an external power source. Unless it was a purpose built brushless generator, then its big$$$. 

Have you figured out the HP of the steam engine, is it enough to run a 100W generator, about 1/2hp or so would be needed.


----------



## metaltrades01 (Aug 27, 2012)

Ed T said:


> You might also want to take a look at a small alternator like those found on small tractors. I have a KUBOTA lawn tractor and it has 10AMP 12v alternator that is about the size of a large tuna fish can. I don't know if the regulator and rectifier is internal or not, but it's a cute package. Alternators work better than generators at low RPM. WRT efficiency, the overall efficiency of your steam power plant will be lucky to get out of the single digits. Also, assuming you're not planning on high pressure steam, you're going to need a pretty big engine and boiler. Using the three to one ratio suggested above, it will need to be a 1.5 ish hp engine which is bigger than you might guess. Cut lots of sticks for the boiler. It will eat them fast.



Hi Ed,
I looked at what is labelled as a Suzuki Seira here in Oz (small 4WD) and it had a 20 amp alternator which was about 4" dia x 4" long and could be disguised with a  dummy cover to look like a generator.
What put me off was the 20amp output-too high, and it would have to be geared up + drive belt efficiency loss's.
 I planned on building a 1 1/2 x 1 1/2" single to drive it and the steam pressure was going to be around 175/200psi + condensing.

Martin


----------



## metaltrades01 (Aug 27, 2012)

MachineTom said:


> MT, What I was describing is a cutout relay, it only cuts the generator in and out of the circuit, The next step up from that is a regulator, which in the case of a permenent mag genertor dumps the overvoltage to a resistor.
> 
> A brushless type DC motor would work but you need some fancy electronics to make that happen, as well as an external power source. Unless it was a purpose built brushless generator, then its big$$$.
> 
> Have you figured out the HP of the steam engine, is it enough to run a 100W generator, about 1/2hp or so would be needed.



Hi Tom,
After what I have learnt here...I'm thinking I'd use a  standard car regulator, and a brushed DC motor.

I wasn't expecting to need 1/2 HP for 100 watt's, I was hoping for 3/8 to 1/4 HP or less?

my calc's are as follow's (correct me if I'm wrong)...
(1 1/2" x 1/1/2" single cylinder, boiler pressure 175psi + vacuum. guessing 100psi in the steam chest (thinking I can better this), but not sure how much to allow for "valve cut off")

P x L x A x N   =   100psi x 0.125 x (.75squ x Pi) x 500rpm  =  8283   
___________          ______________________________               _____
..........................................all over 33,000                                                                          

= 0.25  Indicated HP

Martin


----------



## Ed T (Aug 29, 2012)

I sent this back through the website e-mail, but it didn't find its way to this thread. Don't know why.
Since it sounds like you're well set up to study electrical stuff, it would be pretty simple to set up your generating device hooked up to an electric drive motor preferably variable speed of some kind. Perhaps you could run it off your lathe. Anyhow, in the simplest embodiment it's some kind of variable speed electric drive connected to the generator. It would then be a simple matter to read the volts and amps into the drive and compare that to the volts and amps out of the generator. I think for this to work properly you will have to load the generator side with something. Say a car head light so it has something to "work" against. Load bank if you have one. From that info you could work backwards from Watts to HP and see where you end up. I'm pretty sure that, in any case, with a separate generator you will need to gear the speed of the generator up from the engine especially if it's a low speed engine. As I recall, chain is the most efficient, but it has some other problems, noise, lube, stretch.


----------



## Maryak (Aug 30, 2012)

I calculate it at 0.33hp (top line = 11044.66)

If it's double acting your result is 2x i.e.0.66hp. Cut off won't significantly effect the result as the steam should continue to do work whilst it expands for the rest of the stroke.

Best Regards
Bob


----------



## metaltrades01 (Aug 30, 2012)

Ed T said:


> That's a good idea Ed, no point in making the engine and its not big enough- could always turn it into a twin or compound I guess.
> 
> Btw, I have searched for Kubota alternators and the smallest I can come up with is 14amp, which is a V belt drive (might be able to mount a coupling on the front) & I'm guessing it needs to be turned at 3000+rpm.
> 
> ...


----------



## Ed T (Aug 30, 2012)

This site has a lot of info on generators vs. alternators. First one on a google search. http://www.venselenterprises.com/techtipsfromdick_files/alternators.pdf. Looks like 2400 RPM is the sweet spot. I don't know if different alternators have different curves, but the point is made in the article that alternators have the advantage of making current at low RPM. If you decide to go with the brushed DC permanent magnet motor for your source, you can gain some advantage by messing with the "timing" of the motor. Basically you rotate the location of the brushes relative to the axis of rotation of the motor. In the simplest case of a round motor housing with a round end cap to which the brush assembly is attached, you can rotate the end cap with little modification and, using your instrumentation, find the optimum timing for max output at the RPM you want to work with. Be sure you keep track of the rotation direction because it becomes a directional device and will not work well at all if turned the other way. What kind of batteries are you charging? I'm not much of an electrical guy, but I'm not sure I understand the concern about too much current. If properly regulated, the system will charge the battery 'til it's "full" and then stop charging. Higher current will take less time to fill it up. We're not talking about putting a million amps into a motorcycle battery, but modern automobile alternators are capable of 90 amps or more and they probably dump that into a severely discharged battery until it's full. The same battery can be charged with a 10 amp charger, it just take a lot longer. A 300 AMP hour battery is going to take 3 hours at 100 amps and 30 hours at ten amps (well not actually, but that's the general idea).


----------



## Noitoen (Aug 30, 2012)

You should look for the amateur wind generators sites. Usually the build all kinds of alternators/generators to work on slow rpm's.


----------



## old-and-broken (Aug 30, 2012)

Alternators in todays cars and other equipment charge the battery even with wide variations in the engine RPM.

The 'regulator' also controls the voltage applied to the magnets in the alternator and increases or deceases the field strength to maintain the needed voltage level for battery charging.  Higher RPMs allow higher current flows into the battery of course.

all this meaning - you will probably need to use the corresponding regulator for whichever alternator brand (chevy,Kubota, etc.) for it to operate in this fashion.  It would solve most of your problem with needing 3500 rpms for a DC motor used as a generator.  

just some advice from an overly talkative stranger,   Good luck with this project.


----------



## ninefinger (Aug 30, 2012)

Look at the system and break it down to deal with each part in its own right then combine the pieces together to get your steam-drive-electric-generating-battery-charging goal.

Using a  (BLDC) is probably the most robust and one of the easiest to set up as a generator.  

The electric generating is easily accomplished with a Brushless DC motor (BLDC) driven by something - in your case a steam engine.  As mentioned these motors are rated by KV and as your steam engine is likely to be low rpm you want to find ther lowest KV motor you can get.  

The output of the BLDC when driven by something is an 3-phase alternating current.  Your application calls for DC to charge a battery.  Simple - a bridge rectifier will change the 3 phase - make it yourself from some diodes 






For a source of inexpensive (relatively speaking) BLDC motors look at on-line far east hobby stores - here is an example http://www.hobbyking.com/hobbyking/store/__4652__KD_63_24L_Brushless_Outrunner_193Kv.html  $55 isn't very bad at all (plus shipping).  So using that one as an example you'll probably need to spin it at ~ 2500rpm to get your desired voltage output.

2500 rpm too fast for your steam engine?  No problem - just use gearing or a belt drive to step up the rpm from the engine to the generator.  A 2.5:1 step up would let your steam engine run at a more comfortable 1000rpm.

After all of that then you can look at adding voltage regulators and such to keep the output voltage constant so you don't cook your battery.

My 2 cents..


----------



## tomrux (Aug 31, 2012)

sorry to burst ya bubble here but there is no such thing as a "brushless" DC motor.

they are sychrnous ac motors driven by an inverter able to convert a dc input voltage into a rotating ac voltgage. normaly three phase.

a sychronous motor, when driven by a mechanical source, will output a basially stable ac voltage level that changes frequency with speed.

a brushed motor when driven will output a DC  voltage that changes level with speed.

losses through rectifiers and regulators are going to more than double you input power requirments.
Keep it simple

pick a few brushed motors and try running them at different speeds till ya get what you need

Tom R


----------



## jpeter (Sep 10, 2012)

I'll add my 2 cents. It was suggested to use an automobile regulator with a permanent magnet motor. Well, auto generators and alternators use a field coil for creating the field. The current through the field coil, thus the strength of the field, is controlled by the regulator so the output of the alternator is controlled by controlling the strength of the field magnitism. A perminent magnet field provides no way to control the output. Permanent magnet generators were sometimes used but controlling the output was problemmatic. One solution was to build the generator with extra brushes on the commutator which then could be selected by relays in the regulator. The cutout relay would today be replaced by a diode. Back in the day there was no good diode to be had.


----------



## Don1966 (Sep 10, 2012)

I guess I need to put my 2C in to. I haven't seen any calculations on power. It takes 746 watts for one HP of mechanic motion. The rule of thumb is to size your engine 1.5 x larger then generator. Of coarse you are using it as a demo and can get by with 1.2 x the generator. This is not an exact figure but I am just keeping it simple here. So if you use an alternator of 12volts and 30 amps you have 360 watts, which is equal to about .5 hp of electrical power multiply that times 1.2 equals to about  .6 HP of mechanical power. Just keep it simple. If you use gears to drive it then figure the ratio for HP.

Don


----------



## gus (Sep 11, 2012)

tomrux said:


> sorry to burst ya bubble here but there is no such thing as a "brushless" DC motor.
> 
> they are sychrnous ac motors driven by an inverter able to convert a dc input voltage into a rotating ac voltgage. normaly three phase.
> 
> ...



Hi Tom ,

Thanks for the enlightment. Was into aeromodelling.Been using DC motors to power model planes.Then came along the "Brushless DC motors". This came with red yelloe blue.I got suspicious. The controls and drive that came along
had three wire connections to motor.Then it dawned on me.Its got to be a three phase motor with inverters.

Gus from faraway Singapore.


----------



## tomol409 (Sep 12, 2012)

All you need can be found on an old car (before alternator era) which would have a proper 12v dynamo with the correct output and an AVC unit with cut-out to control things. This would give the sort of output you need .  The voltage would be regulated - that is high when battery voltage is low and cutting down to low as battery voltage rises.   Try some car breakers yards.


----------



## gus (Sep 13, 2012)

tomol409 said:


> All you need can be found on an old car (before alternator era) which would have a proper 12v dynamo with the correct output and an AVC unit with cut-out to control things. This would give the sort of output you need .  The voltage would be regulated - that is high when battery voltage is low and cutting down to low as battery voltage rises.   Try some car breakers yards.



Hi Tom,

Years back I came across a small slide valve steam engine coupled to a car alternator to generate power at a very remote outback station in Queensland,Australia.Took some fotos.Will post if I can find it.Must be Kakadu??? Crocodile country.

In the workshop, my repairman used an electric motor to drive alternator to charge batteries when our charger packed shop.


----------



## skyline1 (Sep 14, 2012)

Hi Martin,

An old type car dynamo and it's regulator box would probably work for this but a more modern alternator would be an even better solution. 

Although they are alternators they usually have all the rectifying diodes and regulating electronics built in and are designed for just this sort of job, battery charging.

there are a couple of disadvantages though, they need to run at quite high speed 3000 to 5000 R.P.M. and they can be quite large and don't exactly look the part.

D.C. permanent magnet motors of about 180 Watts (about the size you require) are very common in industry for variable speed drives. I have used them myself professionally. They are usually high voltage ones though driven through small thyristor drives. Lower voltage and speed ones are available and are often used for wind turbines.

Small P.M. motors can make excellent generators though. I have two of them. These are the types used for tape decks and V.C.Rs and have very powerful rare earth magnets.There is one of them in the second picture (bottom left, didn't realise it was there actually)

They are powered by small steam turbines so I don't have a problem with speed they run at 30,000 R.P.M.+ in fact they need to run fast to produce sufficient torque. Very strange characteristics little steam turbines !

The larger of the two (couple of pics below) Produces 10-12 Volts at about 250mA (about 4 Watts) which is much less than you are proposing but is a usable amount of power from such a small motor.

I have designed a regulator for them which could be scaled up for your application based around LM317 Regulator chips. It is built into the switchboard you can see in the pictures. The switchboard although not quite finished yet is a real working one.

P.M. Me if you would like details about the regulator. as I have all the schematics and P.C.B. layouts and I may be able to make a P.C.B. for anyone interested.


----------



## metaltrades01 (Oct 15, 2012)

Hi There,
I have been away working out west in a remote location and haven't been able to access to the internet, so its time to catch up.

Thanks for all the advise and info, its much appreciated, up to the last reply i made, I came to the conclusion that I had several options, to use a... alternator, an old car generator, brushed DC motor with integral gearbox similar to what is used on bicycles etc (and available on ebay) and i think there a couple of other options mentioned.

Just before I left I spoke to a tech guy involved in renewable power generation, who said that any method that I planned to use to gear up an alternator or generator is inefficient and would soak up a lot of power, and advised me to use a permanent magnet DC motor and direct couple it to the steam engine.

He went on to say "Motors and generators like this are rated at xxx volts per rpm, or xxx rpm per volt, so this motor is rated at around 1800/72 or 25 rpm/volt and 0.04 volt/rpm.  This means that at 300rpm it will produce 12 volts open circuit, so it is pretty much in your required rev range. To charge a battery you would need it outputting around 15 volts, which would take 375rpm."

After the conversation I bid and won a brushed dc motor on Ebay from the US. 

(As a side note...firstly I direct coupled the DC motor to a 12v 5amp fan, and then secondly to a car ventilation/air conditioning fan (amperage unknown) and to my amazement on both occasions the fans turned as i turned the DC motor by hand- so the motor must have a reasonable output).

So the question is now, how to regulate it...


----------



## gus (Oct 15, 2012)

Your DC Gen. looks like the real A.C. Genset I worked on.

Wow ! Mini Street Lights too.


----------



## Ken I (Oct 16, 2012)

A.C. servos used on NC & robotic aplications also make good generators - being permanent magnet rotors with three phase windings for vector driving to position - quite often these motors are scrapped because of encoder failure even though the motor is still good.

Typically 200V = 3000 rpm and whatever Horsepower its rated at it will do as a generator.

These things come in sizes from watts to kilowatts.

Try any local NC or robotic supplier and see if they have any scrap motors.

Ken


----------



## skyline1 (Oct 16, 2012)

Hi Fellas

Gus,

Glad you like It . I've worked on full size ones myself too so I tried to make it look like one of the little private sets of the early 1900s when electrical power was pretty new and there was no grid as such. They were all different some A.C. some D.C. and used all sorts of different Voltages and Frequencies.Typical outputs were in the 25 - 50KW range.

A little imagination is required here, This one has been upgraded to one of those new fangled "turbine" engines but we've kept the old boiler. the "Electric Mechanic" loves it, but the Boilerman hates it says it's too noisy.

This sort of thing was often the case in full size with these things evolving and being upgraded as technology progressed.

Little turbines are ideal for this sort of thing and they make a super sound, real high pitched turbine whistle, at full speed it must actually be ultrasonic 'cos it sometimes makes the local dogs howl.

Martin,

Here's a pic of my LED regulator and I've P.M.ed An Idea for a battery charging circuit to you. Should be fairly simple to build on a piece of Veroboard or a little P.C.B.




Glad to learn about your motor now you know it actually works it's just a question of getting it to charge a battery. This might interest you. more little Permags in action.




This is my little model showman's engine with it's mini dynamo.




And the little Chair - o - Plane ride that it drives just like full size, I've got a video clip of it somewhere doing it, if I can find it I will upload it and put it on the forum

Regards Mark


----------



## jpeter (Oct 16, 2012)

Here's and ebay link to what you need. http://www.ebay.com/itm/DC4-5-32V-t...754?pt=LH_DefaultDomain_0&hash=item3f1d9240ca

It's a dc to dc converter. You input most any dc voltage and it'll output whatever dc voltage for which you've set it.


----------



## jpeter (Oct 16, 2012)

Just a little history:
Back in the day cheap charging systems, motorcycles, 3-wheelers, etc, often used permanent magnet alternators. Diodes were used for rectification. Your motor, most likely, uses brushes to rectify the AC. Anyway, these PM units generally had two charging rates, controlled by switching between a full wave or half wave rectifier. Which to use was often determined by whether or not the lights were on. The light switch was often double pole having a seperate set of contacts to do the switching. Sometimes a regulator did the switching. 

An interesting tidbit:  Motor volts/rpm is commonly referred to as KV.

Automotive generators/alternators use regulators to control the strength of the field magnets. They do this by modulating the current through the field coils. More current means stronger magnets thus higher output. A PM generator, of course, has no field coil to control so controlling the output requires some type of work around. That's why, in an earlier post, I recommended a DC to DC converter. BTW, I've never used one in that service but it seems like it outta work well and ebay has them for pretty reasonable prices.


----------



## albertorc19 (Oct 16, 2012)

You may take a look at www.jameco.com. Those guys have a lot of electronic kits at reasonable prices. Look for Jameco part No. 2161369, it isn't a regulator but may be useful for your project. You can also look for a kit based on the UC3906 which is an integrated circuit (IC) specifically designed to control the charging of acid lead batteries, this IC's data sheet provides schematics for a complete circuit but you need some experience on assembling electronic circuits. Altronics sells a basic kit that seems to be based on the manufacturer's data sheet.


----------



## metaltrades01 (Oct 17, 2012)

Thanks for the info, I'm thinking that i will use a basic regulator to start with and at a later date get a high tech regulator like this one...   http://secure.oatleyelectronics.com//product_info.php?cPath=21&products_id=832    ..which the Tech guy I recommended it to me yesterday, 

& he goes on to say...
 "you could also look at a maximum power point tracking unit, these will take a variable input voltage considerably higher than the battery voltage and step it down to the correct voltage while boosting the current, so if you have 5 amps coming out of the generator at, say 20 volt, you might have 6 amps or more going into the battery."   ....something I didn't know existed.


----------



## metaltrades01 (Oct 17, 2012)

In the next few weeks (or more - as the boiler I plan on using is out of commission at atm) I'll couple the generator to a 2 1/4 x 2 3/8" steam engine I have, and give it a test run, the engine is considerably bigger than the 1 1/2 x 1 1/2" engine i plan on driving the generator with, but it will give an indication of output etc.

I presume that it is possible to post short video's here.?  ...if so, i'll post a vid of it running


----------



## jpeter (Oct 18, 2012)

In recommending the dc to dc converter I'd missed the point about battery charging. I thought the goal was to have a constant voltage output from a variable voltage input even if the generator was turned so slow the generated voltage was below the needs of the load. The buck/boost dc to dc converter provides a constant voltage output for lighting lights and such even if the input voltage is too low. With the mppt controller I'm curious what happens when the input voltage drops below the desired output voltage. Is the controller able to boost the voltage to the desired output voltage? Interesting discussion here.


----------



## gus (Oct 18, 2012)

metaltrades01 said:


> Thanks for the advise Albertorc19, I don't know a lot about electricity generation. I'll go with the regulator.
> I'd be keen to see the results that you get.
> 
> Martin



Hi Martin.

Been using AVR with AC gensets.Therefore know nuts about DC Voltage regulator. As a young kid saw my uncles replacement them on their cars in the 1950s when dynamos were used and alternators yet to be born.


Please advise source of DC Regulators.


----------



## skyline1 (Oct 19, 2012)

Hi Jim

I may be wrong here but I think these MPPT regulators are a form of HF Buck/Boost regulator but with added feedback to monitor the battery voltage and current and hence it's charge state. So they probably can boost the voltage to a degree but naturally at the expense of current.

Being High Frequency switchmode units they can be made quite efficient without the need for bulky transformers..

Regards Mark


----------



## skyline1 (Oct 19, 2012)

Hi Gus

An AVR is a D.C. Regulator of sorts as it controls the field of the alternator and hence it's voltage output.

I was involved with testing some motors for the Canadian Navy which required a locked rotor test for 30 Seconds at full voltage We had to hire a 2MVA containerised genset to do it. The AVR on it couldn't cope with sudden high loads like this so we had a manual one, me ! I though I had met my maker when they put the load on, the noise and vibration inside there was incredible and it nearly stalled the genset. 16 cylinders 2 Turbos and heaven only knows how many litres (about 20 I think maybe more).

Regards Mark


----------



## charlesfitton (Oct 19, 2012)

..still not sure why you don't go to a single terminal, self regulating alternator... apparently it doesn't even matter which way it turns..


----------



## mu38&Bg# (Oct 19, 2012)

Most MPPT solar regulator will not boost voltage. This is because a solar panel making low voltage will also make very little current. The panel is most efficient at 17-19V on a 12V system so the MPPT need only buck mode operation.

Alternators are not very efficient. There is also the need for greater efficiency loss( gears or belts) to get the alternator to a speed at which it makes power. If it's necessary to speed the generator up use gears or light timing belt.

I would use a brushless DC motor wound to generate the appropriate voltage. Assuming the steam engine has a governor, the generated voltage, after rectification, would peak at the battery float voltage. As the system load increases and battery voltage drops, the governor would increase the steam engine torque output to supply current. This of course depends on how sensitive the governor could be. At 400 RPM this would have to be a large diameter short stack motor with a large number of poles.

Another option, I think, is to generate ~110VAC connected to a ac/dc power supply set to the battery float voltage. In general power supplies will operate over a fairly wide range of power input /frequency and are already regulated on the output. Possibly some form of current control ( even as simple as a resistor) would be needed if the system was connected to a battery with a very low voltage to prevent the power supply's over current protection from tripping. Efficiency is quite good. This would be a plug and play solution after the appropriate single phase generator motor was sourced or rewound. Getting ~60Hz from 400RPM would require 18 poles.

There will be losses no matter what generator system you choose. There are many ways to skin this cat, and if efficiency is the goal it can get complicated. Efficiency is important because the more efficient the generator is it's compounded by the steam systems efficiency. So a small change in generator efficiency can result in a large change in the amount of energy required in wood to feed the boiler.

BTW, what is the scenario where steam is the only form of power generation?


----------



## jpeter (Oct 19, 2012)

Someone used the word dynamo. From what I remember, back in the day converting dc voltage from low to high was quite an involved project. High voltage was needed too because electron tubes needed high voltages for plate voltage. One solution was to use a thing called a vibrator which, simply discribed, worked like a buzzer to make and break a low voltage circuit at a prescribed frequency, determined by the mechanics of the thing. That stop and start  flow of current was used as a quasi AC which could then be transformed in the normal way, transformer, to high voltage and then recitified to DC for high voltage DC applications. When more current was needed a different approach was used. A motor was attached to a high voltage DC generator to create high voltage. These units were generally packaged in a tube like configuration with the motor on one end and the generator on the other on a common arbor. These were referred to as dynamos.
  To my knowledge DC generators that used commutators and brushes to  commute the voltage to DC were always called generators. 
  Interestingly, most dictionaries refer to any dc generator as a dynamo. So go figure.

Bottom line is, I  think maintaining adaquate control of the output voltage generated by a permanent magnet dc generator turned by a steam engine is going to require some type of complex electronic switching regulator, dc to dc or mppt, etc., or a really good governor on the engine. Without such you're going to not light lights, burn out lights, boil out batteries or drain batteries back into the generator. (The governor idea might not be a bad one.)

I may be wrong but I love this discussion.


----------



## charlesfitton (Oct 19, 2012)

So somehow this:

"I would use a brushless DC motor wound to generate the appropriate voltage. Assuming the steam engine has a governor, the generated voltage, after rectification, would peak at the battery float voltage. As the system load increases and battery voltage drops, the governor would increase the steam engine torque output to supply current. This of course depends on how sensitive the governor could be. At 400 RPM this would have to be a large diameter short stack motor with a large number of poles.

Another option, I think, is to generate ~110VAC connected to a ac/dc power supply set to the battery float voltage. In general power supplies will operate over a fairly wide range of power input /frequency and are already regulated on the output. Possibly some form of current control ( even as simple as a resistor) would be needed if the system was connected to a battery with a very low voltage to prevent the power supply's over current protection from tripping. Efficiency is quite good. This would be a plug and play solution after the appropriate single phase generator motor was sourced or rewound. Getting ~60Hz from 400RPM would require 18 poles."

is somehow simpler than a couple of pulleys and a self regulating device that is intended to charge batteries (which, when all is said and done, is what the gent wants to do...)


----------



## mu38&Bg# (Oct 19, 2012)

charlesfitton said:


> is somehow simpler than a couple of pulleys and a self regulating device that is intended to charge batteries (which, when all is said and done, is what the gent wants to do...)



If you have any concern about the efficiency of the system, it matters. For simplicity sake do whatever you feel works.

There is also this concept which does away with the need for steam altogether.

http://en.wikipedia.org/wiki/Thermoelectric_generator
http://tegpower.com/products.html

Greg


----------



## skyline1 (Oct 20, 2012)

I think Greg's solution would work but I agree about it being a little complicated and whilst 110VAC is not considered a dangerous voltage it could give you a bit of a shock if you touched it especially if it was single ended not centre tapped to earth as is the common practice, granted you would have to touch both poles at the same time if it was  fully floating, and as power supplies tend to have about an 85% efficiency or lower at the extremes of their voltage range  nothing much would be gained here as the efficiency of the MTTP regulators Martin mentioned is similar. This idea would reduce I squared R losses, which is why mains power is transmitted this way, but as we are talking about smallish currents anyway I don't think the gains would be that great.

He is right about the number of poles I'm talking about European here but at 50Hz synchronous speed for a 2 pole A.C motor is 3000 R.P.M. so for 375 R.P.M.  ( 3000 / 8 ) you would need 2 * 8  = 16 poles  A 110V 16 pole permag alternator. would be a pretty complex expensive machine and probably hard to find.

As Martin already has a usable D.C. generator his best bet is probably to stick with it and accept that it's not going to be wonderfully efficient. I have found that in small scale frictional and thermodynamic losses tend to be much more of a problem that electrical ones anyway.

Regards Mark


----------



## metaltrades01 (Oct 22, 2012)

charlesfitton said:


> ..still not sure why you don't go to a single terminal, self regulating alternator... apparently it doesn't even matter which way it turns..



An alternator need to be turn at about 2000rpm + to start to develop a current, so it would have to be geared up via a chain or belt etc, which introduces loss's that I can't afford.


----------



## metaltrades01 (Oct 22, 2012)

I thought i'd already posted these test result from a few days ago...

On the advice of a previous post on this thread, I have just load tested the generator on a small lathe that is fitted with a digital rpm indicator.

At 460 rpm it produces about 13 volts, which is what I was after. I had a small 12v car driving light as the load and it drew 4.6 amps.

I increased the load to 2 driving lights and the the overload tripped on the small lathe that I was using at about 240 rpm.

I held the shaft in the chuck and held the generator by hand, considering the load with one light, I'm confident that the engine will be able to turn the generator at full load.

I'll fit a coupling to the generator and bolting it down to test it on a steam engine, and see what the max output is at around 13.5 volts .


----------



## gus (Oct 23, 2012)

skyline1 said:


> Hi Gus
> 
> An AVR is a D.C. Regulator of sorts as it controls the field of the alternator and hence it's voltage output.
> 
> ...



Hi Mark,
Were you testing an alternator or synchronous motor? Sounds scary.Am glad ,I was never involved with locked rotor testing.

The biggest Synchronous motors I started up in 1975,were two EM 1500hp motors coupled to Ingersoll-Rand Centacs Centrifugal Compressors. MG(motor generators) were used to provide D.C. for the exciter rings. Starters were reactor type which made lots of noise on starting.We had the HT starter supplier/builder to help us with startup. Auto Trans starter is practically noisless except for the humming.The reactor trans starter had 100 cats screaming away on starting.

During startup,the shipyard engineers quietly disappeared leaving us alone.


----------



## skyline1 (Oct 24, 2012)

Hi Gus

They were 50KW synchronous motors for starting up the gas turbines on Naval frigates  so they had a very high spec on them. In use they have a very high starting load so they need to be able to withstand being stalled for a couple of seconds. With the rotor locked there is very little back E.M.F. so the supply "sees" a near dead short. hence the huge genset. For this reason locked rotor tests are usually done at much reduced supply voltage and the results extrapolated.But not so in this case. It certainly tested the motors and also the genset, and me !. According to my colleagues it made the ground shake and the set emitted a huge cloud of black smoke every time we did it.

We used reactor starters on some rotary frequency converters we made at the same company they were so noisy that they were mounted in soundproofed enclosures. After having had two of them catch fire on test it was discovered that the manufacturers had got one winding out of phase. That made them even noisier and prone to overheating and bursting into flames.

Very strange machines they were used to power the I.T. gear in a big  datacentre for a bank. and the output frequency was 440Hz (Middle A on a  piano) deliberately designed that way so they could check the speed  with an old fashioned tuning fork.

Working on the test bed at that place could be pretty "Interesting", minor fires and flashes and bangs were a regular occurrence. We even caused the complete evacuation of the factory once. It was an "authorised admittance only" area for obvious reasons, but even people with a legitimate reason to be there had a sudden desire to be absent if we had a "big 'un" on test. Half a ton of armature has a lot of inertial energy at 1000 R.P.M. and doesn't like being brought to an instant stop. It complains very spectacularly and dangerously !

Regards Mark


----------

