Lister Engine Forum
How to / DIY => Generators => Topic started by: Procrustes on August 12, 2006, 07:49:04 AM
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I'd like to understand better how flywheels help start induction motors. I understand that they store inertia and thus are well suited to the peaks that electric motors require. Why then does the SOM have a 2.5kW head? A standard 6/1 ought to be able to output 2.5kW continuous, so I don't see what advantage the oversized flywheels on the SOM confer, other than steadier output.
Also, I've heard that a 6/1 can output 3.8kW at sea level. Is this peak or continuous? If not, what is peak power? How would heavier flywheels affect peak output?
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Flywheels store energy. This energy can be unloaded very quickly as opposed to waiting for a power stroke from a piston. The faster the flywheel is spinning, the greater the rate of energy delivery to the load.
Peak power demands by a large load... Say a big induction motor on an air compressor can be extremely hard to start without a flywheel system. In order to start these kinds of loads, you either need to oversize the engine and the generator head, or you add flywheel mass. From an expense point of view, the cheapest place to add flywheel mass is on the generator head.
It is my view that the Lister orginal equipment, such as the SOM, were underated. These engines were really designed to serve industry. I do not have a 6/1, but it is my understanding that they can output 3.8kW continuous. Peak power on something like that can exceed 5kW for a very short period of time... Initially the load would be served by the flywheel, then the rack would open up.
Heavier flywheels permit higher peak power to be delivered. Faster spinning flywheels permit the power to be delivered at a faster rate.
Continous power is the rated HP output of the piston. Peak power is the rated HP output of the piston, plus the stored energy in the rotating mass: crankshaft, flywheels, generator rotor, and any additional masses such as pulleys or shafts.
I am currently designing a jackshaft for PTO from an engine system. The jackshaft will rotate at 1800 RPM and permit direct coupling of the generator head. The rest of the high speed shaft is available for mounting flywheel mass and for additional PTOs. Because of the higher speed, I am planning on boring and milling out junk steel flywheels from trucks and tractors and stacking them on the keyed jackshaft. This shaft will not increase the total horsepower, but the peak power would be increased dramatically, as well as the peak power delivery rate... Because of the stored energy in the shaft. Hard to start motors and other loads with high torque requirements can be started in many cases before the rack has a chance to respond.
One of the problems with having a generator without a flywheel in the system is with starting big motors and air conditioners, especially capacitor start electric motors. The generator may have a continous output rating sufficient to run this type equipment, and still be unable to start it. This really tears up the motor because they get very hot quickly if they are not brought up to speed rapidly. The commerical equipment that does not use flywheels get around this by running the engines and generators at higher speed, usually 3600 RPM. The increased shaft speed increases the delivery rate and makes starting big loads a little easier... But even at 3600 RPM, most generator set are not going to have a great deal of peak power available because they lack flywheel mass.
Another way to look at this is compare a Lister type engine with a gas or diesel modern engine running at higher speed, but with the same HP rating. The modern engine will have a faster delivery rate, but the Lister type will have greater peak power due to the flywheels. If you look at the SOM you will see the orginal equipment has added flywheel mass on the generator pulley. This provided an increase of peak power, and in delivery rate.
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I'd like to understand better how flywheels help start induction motors. I understand that they store inertia and thus are well suited to the peaks that electric motors require. Why then does the SOM have a 2.5kW head? A standard 6/1 ought to be able to output 2.5kW continuous, so I don't see what advantage the oversized flywheels on the SOM confer, other than steadier output.
Also, I've heard that a 6/1 can output 3.8kW at sea level. Is this peak or continuous? If not, what is peak power? How would heavier flywheels affect peak output?
Procrustes,
On average a 6/1 will carry 3300 watts with a st5 gen head, that represents a loss of 1174 watts in the transmission (belt) and gen head windings. Not taking into consideration the slight loss of the belt drive the st head is approximately 73% efficienct in converting mechanical energy into electricty.
If maximum efficiency is the main priority the most efficient way of producing electircty with the 4474 watts (6hp) available would be IMHO to use a dc permant magnet generator as they can be as efficient as 90% then convert to ac using an inverter as they average around 95% efficient. That would be a total loss of 15% rather than the 27% loss incured by the st head.
Or the totals for the two systems look like this.
ST5 = 3300 watts dc to inverter = 3803 (likely your 3800 #)
Peace&Love :D, Darren
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I'd like to understand better how flywheels help start induction motors. I understand that they store inertia and thus are well suited to the peaks that electric motors require. Why then does the SOM have a 2.5kW head? A standard 6/1 ought to be able to output 2.5kW continuous, so I don't see what advantage the oversized flywheels on the SOM confer, other than steadier output.
Also, I've heard that a 6/1 can output 3.8kW at sea level. Is this peak or continuous? If not, what is peak power? How would heavier flywheels affect peak output?
Procrustes,
On average a 6/1 will carry 3300 watts with a st5 gen head, that represents a loss of 1174 watts in the transmission (belt) and gen head windings. Not taking into consideration the slight loss of the belt drive the st head is approximately 73% efficienct in converting mechanical energy into electricty.
If maximum efficiency is the main priority the most efficient way of producing electircty with the 4474 watts (6hp) available would be IMHO to use a dc permant magnet generator as they can be as efficient as 90% then convert to ac using an inverter as they average around 95% efficient. That would be a total loss of 15% rather than the 27% loss incured by the st head.
Or the totals for the two systems look like this.
ST5 = 3300 watts dc to inverter = 3803 (likely your 3800 #)
Peace&Love :D, Darren
Cut the shit darren, you don't own a 6/1 so you haven't got a fucking clue how efficient they are.
How efficient is my start-o-matic when producing 2 Kw of AC?
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It all goes back to E = M V2. For a flywheel, the amount of energy stored in it is applied to the gen head when you have a demand that is larger than the Listeroid can put out at that instant. Meaning when you have a momentary load (starting a large motor) the gen head draws its energy from the flywheel rather than the engine and then the engine picks up the load. Sorta like a capacitor in electrical loads. The M is the mass of the flywheel itself, the V is the velocity of the flywheel. Velocity is worked out at each distance from the center for what ever mass is at that distance.
Velocity (might as well call it rpm) supplies energy as its square, mass at a straight line. Whatever energy you dump from the flywheel has to be put back into it from the engine.
This is why I'm planning on integrating extra flywheel into my setup. On a jackshaft with its own bearings, setup wwith a clutch to take it out of the drivetrain when necessary.
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Consider a solid disc flywheel of radius 50 cm and mass 140 kg. How fast would it have to spin to have a store the equivalent amount of energy that is stored in just 10 kg of gasoline when burned in an internal combustion engine:
* 10 kg of gasoline = 140 KWH
* Engine has 15% efficiency --> 21 KWH of useable energy
* Flywheel has a conversion efficiency of 80%
* Flywheel must therefore store 21/.8 = 26.25 KWH
* Kinetic Energy goes as 1/2*I*w2. For flywheels I =1/2MR2.
* If we measure w in revolutions per second then the stored energy of a flywheel is approximately 6MR2 x w2 (RPS)
* For M=140 kg and R=50cm this yields a required w of 500 RPS or 30,000 RPM
A CS 6/1 Start-o-matic flywheel *each* weighs approx 136 kg, and has a radius of approx 33 cm
Obviously 650 RPM = 10.83 Revs per second, hell of a lot less than 500, but still... do the math.
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Thanks for the replies everyone. However I still don't understand what good the huge flywheels are on a SOM if it has a 2.5kW head; it should be able to produce that much power continuously. What am I missing?
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A single cylinder engine only produces 1 power pulse for every 2 revolutions so there needs to be heavy flywheels to carry the engine through the non-power strokes of the cycle without causing significant slowing of the generator that will cause flicker in connected lights. This is a prodlem with ANY single cylinder engine and is more pronounced at slower rated speeds and particularly on 4 stroke cycle engines with the longer 'coast' times between power impulses.
By derating the output the manufacturers could also achieve two goals; the maximun output would appear higher on their 2kw unit and there would less likelyhood that the engine would slow enough to cause the enoying flicker. This was especially important to Lister since they were marketing a high quality light plant. Fairbanks-Morse also employed huge flywheels on their engine and derated them slightly when those engine were to be fitted to a generator for lighting for these same reasons. Kohler was one of the first to offer relatively low hp engines with multiple cylinders for light plants as a way to overcome the need for huge flywheels to minimize flicker.
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Listeroids can cause lights to flicker. The voltage climbs and drops in sync with the combustion stroke. A voltage regulator can help this, as do heavier flywheels.
While Darren has done his math and is correct, he makes one serious error. The 6-1 will make well more than 6HP contin. I have seen better than 4000 watts with black smoke and 3800 with minimal smoke. Any way you look at it the engine makes more HP.
Chris
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Kohler was one of the first to offer relatively low hp engines with multiple cylinders for light plants as a way to overcome the need for huge flywheels to minimize flicker.
This is a good point, considering twin Listers and triple Petters are available. If flicker is an issue....
Doug
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Listeroids can cause lights to flicker. The voltage climbs and drops in sync with the combustion stroke. A voltage regulator can help this, as do heavier flywheels.
While Darren has done his math and is correct, he makes one serious error. The 6-1 will make well more than 6HP contin. I have seen better than 4000 watts with black smoke and 3800 with minimal smoke. Any way you look at it the engine makes more HP.
Chris
The peak horsepower of a 6/1 is not the point I was trying to get accross hense the word average.
The point was that if you are shooting for maximum efficiency of the transfer of mechanical energy to electrical power the st style heads are not the best choice.
If your set will carry 4000 watts with a st then it would carry approx 4480+ with a permant magnet dc genny and efficient inverter.
All the very efficient Honda portable gennys are producing power this way and yall probabally know as well as I do Honda doesnt fuck around.
Peace&Love :D, Darren
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Find me a PM generator that turns slow, a load sencing system that can varry the speed of a stationary engine to match, an inverter with a DC link ( AC-dc-AC ) and do this all under 500 bucks and you will have my attention. Untill then I think the ST head is dollar for dollar the most cost effective way to achieve the desired result.
Yes Darren it would be great to have an inverter generator with a low speed stationary engine. But I don't think anyone could fix it. The failure rate for even the best electronics still leaves you with the probability that the engine will long out live the Inverter and ther guy with an ST Lister combo will have lights on longer even if he burns more fuel.
Last but not least I don't know if the small increase in power is worth the trade off. I still think an ST will more reliably handle a surge than a bank of IGBTs....
Doug
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A single cylinder engine only produces 1 power pulse for every 2 revolutions so there needs to be heavy flywheels to carry the engine through the non-power strokes of the cycle without causing significant slowing of the generator that will cause flicker in connected lights. This is a prodlem with ANY single cylinder engine and is more pronounced at slower rated speeds and particularly on 4 stroke cycle engines with the longer 'coast' times between power impulses.
Exactly.
Now there are other options to keep lights from flickering. The one I prefer is electronic regulation of the output. Of course the frequency will still vary, but for household loads this is not always a problem. There is one bugaboo with electronic regulation: In order to remove the flicker, the electronic regulator has to have a fairly fast response time - faster than the flicker rate of 5 Hz, anyway. This requires that it be able to rapidly change the current through the field winding. I've looked at the inductance of the field winding, and have a design of regulator that should work.
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Do you think a fero-resonat transformer would work? I have no idea of their frequency response.
George
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If you want stability in a stationary setup: the simplest and most reliable, longest lived solution is to add high speed flywheel mass to the shaft driving the generator.
http://listerengine.com/smf/index.php?topic=896.msg11668#msg11668
Note: this jackshaft is being designed for 2 PTOs. The shaft would be directly coupled to an ST15kw head on the left side. The clutch engineering I am designing is for a hydraulic pump and would not be needed on a simple shaft designed for frequency & voltage stability and starting difficult loads.
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I was looking for a little patch of land with 12 foot of head and 2 cubic feet of water flow. I also came to the same conclusion that I would need to add at least 500 pounds of rotating mass 20 inches in diameter in order to slow the response to load changes enough to keep lights from flickering.
I still live in a "Burb", not too happy about it.
Doug
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Do you think a fero-resonat transformer would work?
No. Their output voltage varies if the frequency changes. Any ones I've seen also run hot, so they waste some power.
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Forgot about all that heat!! Really bad idea.
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is having excess heat a bad thing? is it really a loss if it is inside your house in the winter? :)
bob g
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You are correct, Bob. It depends on where you stand, doesn't it?
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Thanks for the replies everyone. However I still don't understand what good the huge flywheels are on a SOM if it has a 2.5kW head; it should be able to produce that much power continuously. What am I missing?
I would guess that that 2.5 KW is the continuous rating, and like most any motor or generator peak output can be very much higher depending on the duration of the event.
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Thanks for the replies everyone. However I still don't understand what good the huge flywheels are on a SOM if it has a 2.5kW head; it should be able to produce that much power continuously. What am I missing?
I would guess that that 2.5 KW is the continuous rating, and like most any motor or generator peak output can be very much higher depending on the duration of the event.
Yes it is a continuous rating, as in 24/7 at full rated output, unity power factor.
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SOMs were made with 5/1s correct? So the engine was rated lower. I would assume (I know I know) that a 5/1 is different than a 6/1... And the kW rating of a 5/1 would be lower.
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SOMs were made with 5/1s correct? So the engine was rated lower. I would assume (I know I know) that a 5/1 is different than a 6/1... And the kW rating of a 5/1 would be lower.
My understanding is that it was called a 5/1 for a while after the rated speed changed. So it was 5 HP @ 600 RPM, or 6 HP @650. Same engine. The torque curve, btw, is pretty much a straight line in this range.
http://www.oldengine.org/members/diesel/Technical/51P4data.htm
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Listeroids can cause lights to flicker. The voltage climbs and drops in sync with the combustion stroke.
Speaking of flickering lights, there's another possible cure that some may favor (I'm rapidly learning to avoid using the word 'simple' on this forum - what's simple for some isn't for others).
Some Onan single cylinder Diesel sets had "flicker points" on them. I've heard of it, but haven't looked at how they imlemented it. My guess is that the points (like points on a pre-electronic ignition system) shorted across a field dropping resistor. The points rode on the cam shaft, and were timed to close towards the end of the exhaust stroke, and open just past TDC on the power stroke. That way, the field excitation current would be ramped up just as the engine speed was slowing down the most.
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Listeroids can cause lights to flicker. The voltage climbs and drops in sync with the combustion stroke.
Speaking of flickering lights, there's another possible cure that some may favor (I'm rapidly learning to avoid using the word 'simple' on this forum - what's simple for some isn't for others).
Some Onan single cylinder Diesel sets had "flicker points" on them. I've heard of it, but haven't looked at how they imlemented it. My guess is that the points (like points on a pre-electronic ignition system) shorted across a field dropping resistor. The points rode on the cam shaft, and were timed to close towards the end of the exhaust stroke, and open just past TDC on the power stroke. That way, the field excitation current would be ramped up just as the engine speed was slowing down the most.
Another way that could be implemented would be with an ignition type capacitor instead of a field dropping resistor. When the capacitor closes it would boost the field.
Flicker is going to be seen as a result of both a drop in frequency and voltage... This is not going to help the frequency sag, but with a small voltage boost at the right time most of the flicker could be eliminated so that it would not fatigue the eyes.
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Ignition type capacitor? You mean the little .1 uF caps used in distributors? That would not be large enough to boost the field supply significantly.
The field draws around 2A, and it needs to be boosted for 1/2 of an engine revolution - about 1/40 s at 600 rpm, That will require many 1000's of uF's.
If we keep the voltage constant, how would a drop in frequency cause visible flicker in an incandescent light?
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Ignition type capacitor? You mean the little .1 uF caps used in distributors? That would not be large enough to boost the field supply significantly.
The field draws around 2A, and it needs to be boosted for 1/2 of an engine revolution - about 1/40 s at 600 rpm, That will require many 1000's of uF's.
If we keep the voltage constant, how would a drop in frequency cause visible flicker in an incandescent light?
I said type, I did not specify size really... And it will work and it won't require many 1000's of uF's. The capacitance cancels some inductance in the field winding, it does not make much difference how long it stays in the circuit it's job here is not to deliver a pulse of energy but to continiously cancel winding inductance and increase current flow. As far as size goes, you might need something between a standard ignition capacitor and a motor start capacitor... But it's not going to take something huge. I have seen big ignition type capacitors for aftermarket/performance/race coils back in the 60's and 70's that I think would work fine. Same type, same construction, same voltage rating would work here... You would have to play with the size because too big of one will cause surges in place of your drops.
As for voltage/frequency drops in lighting applications: When you have flicker you are seeing the voltage drop because the frequency is lagging during portions of the engine cycle. If you engineer a solution to boost the field voltage during this portion of the cycle, as we have been discussing, the visible flicker is resolved, what remains unresolved is the frequency sag... The energy looks smooth to the eye, and the eye will not resolve the frequency lag in lighting applications... Good enough for government work, but in a power processing research application such as I intend to run, frequency sagging is unacceptable.
I intend to put high energy physics loads on my equipment. Some drift is acceptable (such as rack changes to accomodate loads), but sagging during engine cycles, every cycle, is going to give me headaches. The other problem with the type equipment I run is that it is even harder to load up than say dropping an air compressor motor and an arc welder on at the same time... Huge inductor masses (in fact I have loaded shorted out arc welders on as ballast)...
I need clean, stiff, energy out of a system that would want to drag the engine around by the nose.
I will post some pics, then you will understand better.
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http://listerengine.com/coppermine/displayimage.php?album=101&pos=2
^^^ Preamp
If you are processing raw power into a power amplifier, frequency sags are propagated thru the system and are amplified as well... The result is distorted output, exactly like the distortion seen/heard in audio amps when either the input signal is not clean, or the amp is clipping. In this instance, you could actually document frequency sagging with the naked eye if you used a one second exposure of the test arc... And as you amplify the pre-amp output, the distortion just gets more pronounced.
http://listerengine.com/coppermine/displayimage.php?album=101&pos=3
^^^ Hard starting load - This is another preamp configuration... Energizing the cores on these loads stalls the engine on a 5 HP gas generator when you throw the switch.
http://listerengine.com/coppermine/displayimage.php?album=96&pos=1
^^^ Frequency stability and load starting. This is my working design for an 1800 RPM jackshaft with steel flywheels. The shaft would be belt driven from the engine, and the generator would be direct coupled to one shaft end. The flywheel mass and higher rate of rotation should really improve the "flicker" quality of the input signal and provide torque on demand at a high rate of delivery to energize my physics loads.
http://listerengine.com/smf/index.php?topic=634.msg8830#msg8830
^^^ Interesting post noting the effect of poor waveform on microwave ovens...
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I don't remeber anything like this on the CK CCK or the 3600 rpm engines....
I think you just turned on your lights and smiled. They were good plants.
Doug
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Right, akaik, they only showed up on early the DJA sets (single cylinder Diesel, 1800 rpm.)
Interesting you mention the CCK sets. I have an old one here, and the engine has a lot of blow-by. Probably not worth fixing. But I'd been thinking that its 1800 rpm alternator might make a nice mate for a listeroid. Biggest problem would be adding a 2nd bearing. The nice thing is that on this set, the alternator has a 12V DC starting motor built in.
I have a schematic showing the flicker point scheme, but it's a pdf. What's the best way to post it ?
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The capacitance cancels some inductance in the field winding, it does not make much difference how long it stays in the circuit it's job here is not to deliver a pulse of energy but to continiously cancel winding inductance and increase current flow.
Kindly show us how that works. I can't fathom it. There's a heck of a lot of things I don't understand in this world. But with 23 years' experience designing electronics for a living I ought be able to get this!
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Jim: the reason the onan at 3600 does not have the issue of flicker is one of resolution
the lower the rpm of the engine and the larger the step up in gearing the resolution works against you
a small change in engine rpm relates to a relatively larger change in frequency compared to a direct drive 3600 rpm genset
if you drop 30 rpm on a 650 engine, that might equate to a 5 hz drop,
the same 30 rpm drop on a 3600 rpm engine is likely less than a hz.
i dunno without doing the math,,, but i have experienced this phenomenon on
home built light plants
the best results i ever got was running the engine at 3600 and gearing down to 1800 or in some cases 1200, thus increasing the resolution and giving a much more stable frequency.
make sense?
bob g
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I dunno but I want to see that print, I don't remeber this flicker crap at all.
The CCK head was if I remember something on the order of 4 or 5 kw. These heads also could motorise and start the engine. Pitty about the engine.
I'll say this again for like the umpteenth time. Indian heads could be adapted to start an engine of somebody over thre would just add a com.....
Doug
Jim I think he;s talking about something that would look like series resonance for a split second...
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...something that would look like series resonance for a split second...
Still doesn't make sense to me. Series resonance involving what inductance - the field???
The pdf I have is my own design, not Onan's. I don't have a manual that covers the DJA sets, but I'd like to see it myself.
Yes, Bob that makes sense. The flicker problem gets worse with slower speed engines, single cyliner engines, and with Diesels since the energy required to get past TDC on the compression stroke is greater than with a gas engine.
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The capacitance cancels some inductance in the field winding, it does not make much difference how long it stays in the circuit it's job here is not to deliver a pulse of energy but to continiously cancel winding inductance and increase current flow.
Kindly show us how that works. I can't fathom it. There's a heck of a lot of things I don't understand in this world. But with 23 years' experience designing electronics for a living I ought be able to get this!
No problemo 8)
Let's start with a review of capacitance and inductance. These two values cancel each other out. If the value of the capacitor exactly cancels the inductance of a coil... As far as the resulting circuit is concerned, only resistance remains. This is the basic principal of the LC oscillator.
http://www.electronixandmore.com/articles/oscillators.html
http://en.wikipedia.org/wiki/LC_circuit <- Da math
Now, if you put a capacitor value across the rotor that canceled the inductance completely, you would end up with a resonate circuit that would increase the harmonic distortion of the generated energy. This would be the result of using the large capacitor you described on an ST head, and on an iron cored coil such as an ST rotor you are probably correct in that it would take a huge capacitor value to cancel the inductance completly. Yet... This is not what we want.
The lightbulb in my head went off when you mentioned that with a cam driven set of points, the capacitor would only be in the circuit for a fraction of the engine rotation period, and it would be closed in the circuit only when a voltage boost was required to overcome flicker. During the period of time when the capacitor would be in the circuit a complete canceling of the inductance is not required, we would only need to cancel enough inductance to boost the current flow thru the rotor and preventing voltage from dropping.
With an inductance meter measurement of the rotor inductance, and a scope measurement of the voltage drop causing the flicker, you can calculate the value of the capacitor required to boost the rotor current by a given percentage... Let's say a 10% voltage drop is resulting in flicker, you cancel 10% of the rotor inductance (a reasonble sized capacitor) and switch that in with cam operated points...
Now, with that in the can... Let me qualify this by saying I have never done something exactly like this... I have done my fair share of PFC math in order to completely cancel inductance in power processing applications (the BIG capacitors you described)... And the exact same principal is applied to the primary coil of the old style point driven spark ignition systems... It is also the basis for LC oscillators... All of these applications I am very familiar with. In this particular application you don't want or need enough capacitance in the circuit to create a completely canceled condition of the inductance (aka PFC correction in a power circuit or LC oscillator functions) you just want enough capacitance switched in to correct the voltage drop resulting in flicker.
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Still doesn’t add up in my head, Rtqii. You describe a parallel LC circuit, like PFC caps, right? Whenever I’ve used PFC caps, the load current (the current through the inductive element) doesn’t change for the addition of the caps. Of course the line current (the sum of the load and capacitor current) drops, but the inductor current remains the same.
PFC caps aside, here’s the way I look at it, and the reason I think caps won’t work: The fundamental 60 Hz AC output from the stator (which is what we want to boost, right?) is a function of the DC flowing through the field. The caps are an open circuit at DC, and therefore have no effect on the DC component. Therefore, I can not see a mechanism by which adding capacitance across the field will change the DC component of field current. If you can’t change the DC component of the field current, you won’t boost the 60 Hz AC output.
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Jim I don't know now....
I need to see a print, and my manuals for the Onans are at camp ( where the Onans are... ). I thought I gasped what he was trying to explain and it seemed to make sence to me but I was also enjoying some cool refreshing beer.
Doug
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Still doesn’t add up in my head, Rtqii. You describe a parallel LC circuit, like PFC caps, right? Whenever I’ve used PFC caps, the load current (the current through the inductive element) doesn’t change for the addition of the caps. Of course the line current (the sum of the load and capacitor current) drops, but the inductor current remains the same.
PFC caps aside, here’s the way I look at it, and the reason I think caps won’t work: The fundamental 60 Hz AC output from the stator (which is what we want to boost, right?) is a function of the DC flowing through the field. The caps are an open circuit at DC, and therefore have no effect on the DC component. Therefore, I can not see a mechanism by which adding capacitance across the field will change the DC component of field current. If you can’t change the DC component of the field current, you won’t boost the 60 Hz AC output.
Well... Let's table this discussion until I get my engine and generator and can properly document an experiment. My meters and scope are in storage waiting until the new building goes up, and I just ponied up for the engine and generator today. This is something that won't take a great deal of effort to prove or disprove, once I get my infrastructure in place.
The thing I am looking at in the circuit function I see, is that the DC is not steady state... Not like a battery output. The rotor coil is not acting like a pure permanent magnet... There is magnetic flux in the rotor because voltage is rising and falling with the frequency lags during portions of the engine cycle. I honestly think some capacitance switched in during these lags will result in smoothing the output.
The proof of course is in the pudding... It will take me a few months before I can come back to this with the proper equipment and run some tests, but I don't mind looking into it further then.
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^^^ Frequency stability and load starting. This is my working design for an 1800 RPM jackshaft with steel flywheels. The shaft would be belt driven from the engine, and the generator would be direct coupled to one shaft end. The flywheel mass and higher rate of rotation should really improve the "flicker" quality of the input signal and provide torque on demand at a high rate of delivery to energize my physics loads.
Rtqii,
The high speed flywheel pack directly coupled to the shaft of the alternator is a very good idea. In addition I would highly recommend oversizing the kVA rating of your alternator by a factor of 2X, 3X or more, i.e. use a minimum 40 kW unit if the diesel engine can only produce 20 kW continuous electrical output. The lower Z will really stiffen your supply.
In a multi kVA and larger Tesla coil oscillator with rotary break the use of a break synchronous with the supply frequency really pounds on the alternator and requires an alternator well oversixed for the load. You can get by with a more conservative power source if you stay with higher PPS bang rates (than the mains frequency) like 400-600 PPS and non synchronous operation. High rep rates are much harder on pulse capacitors however and shorten their lifetimes. Engineering is full of tradeoffs. Of course it all depends on what you are trying to achieve.
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Of course it all depends on what you are trying to achieve.
Maximum peak power of course!!! ;D
I tend, based on experience, to think you are very much correct about oversizing the generator set. I know for a fact how hard these circuits are on everything. No sooner do you beef up the weakest component in the system (because the previously engineered component failed in serivce), then the next weakest component in the system fails... When the step up transformer, tank circuit and gaps are all pretty much bullet proofed, the next place to look for a failure would logically reside in the control cabinet & power supply.
I am hoping to keep the actual design, research, and prototyping power levels in the range between 3-6 kW, and figured on installing an ST15kW generator head for the mains supply. I could do an ST20, I held back at the last second on the genhead purchase because I have no place to store it until the shop/lab building is roofed and that is a few weeks away yet. There is a lead time in importing the engine, so I paid for that and held the check for the ST15 back.
There is the inevitable temptation in this line of research to match a larger engine to a larger generator and anybody familiar with this equipment knows there is an infinity quotient directly associated with Tesla's resonance patent... There is no limit to how large and powerful this equipment can be scaled up to. It can lead to bankruptcy.
I have designed, built, and operated Tesla oscillators and resonators in the 10-15 kW range, and having done this I am of the opinion that this is 2-3x above the power levels needed in order to produce viable prototypes and demonstrations of the new applications I have patented. Most of the time I think 3 kW of input power should do the trick, and if it doesn't then 6 kW surely will make my points.
I have liquidated, or am in the process of liquidating, practically all my assets to put this project together... I have the money required to do the job right, but the sky is not the limit. With this in mind, I sized the power plant for dual use... It will run the ranch most of the time, and it will power the research for a small fraction of the time. Giving the balancing act required whenever a project like this is designed, engineered, and paid for... I opted to go with a 20 HP prime mover to turn the generator, and a 15kW ST. I would not consider spending a few hundred extra on an ST20 to be extravagant.
The goal here with the Tesla research is to design, engineer, and prototype patent models for commerical development... Not the commerical applications themselves. Admittedly, I could probably do this work on a much smaller scale, and could even use solid state oscillators... But it would not give people the picture of what a commerical type installation and application would look like... In other words, the proofs can be done on apparatus you can probably hold in your hand and plug into a wall outlet... But in my experience people have limited imagination and are not able to see that scaled up equipment operates on exactly the same fundamental physics, only everything is larger.
So in effect what I am doing is developing a research facility as a scaled down mini-plant... Fuel will come in, drive the prime mover, spin the jackshaft with flywheels and turn the generator.... It will have all of the basic components of a stand alone commerical enterprise, just on an R&D scale.
Good capacitance is expensive... I have some good capacitance with low minutes, and it has never been excited at anywhere near its rated voltage and capacity... They were designed to be tough enough to process 20 kW all day, and should have 72 hours of life in them at 40,000 volts AC rapidly pulsed. I should be able to get many, many research hours out of them at much lower voltages and power levels.
If I were to decide to go with a much larger generator, I would end up moving to higher power levels. If I were to do this I would convert the main oscillators over to 3 phase and pick up a used commerical 3-phase generator to drive it. I suppose this is possible eventually, I have thought about it, but it is not in the cards at this point. I think perhaps what I may do is put some extra floor space in the engine room, leave a blank spot in the floor where a mounting block for this upgrade could be placed in the future... Then, if I see a steal deal on a big 3 phase generator...
But I would not remove the Listeroid and ST genset from service... I still need a primary power supply for the ranch.
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