Tieing Big Bertha to big Bert Generator to Generator

I do not think it a good idea to go to the complexity of trying to synchronise two small generating set.

Can you not divide your load into two parts and run half of each generator.

Rather than to go into the panel and do divide and subdivide, It is much more economical to run Big Bertha at near capacity than at 1/2 capacity, (diesels love to labor) I just need a boost during peak loads when the boss ( read wife ) wants to do the washing, drying, dishwasher, coffiemaker, air conditioner, whilst I am wanting to do some grinding (air compressor) and welding.

seems like I read some where that it was a cinch to sync a inductance motor to another generator.

you have two sources of voltage, both about 60 hertz. You can buy synchronizers, but they depend on a rock steady speed of each generator and you slowly adjust the speed to match. The other way is to make a DC main and run small load sized AC inverters off it. A lot of home power people do this as the inverter is exactly sized to it's load = highest efficiency. They often run on batteries, with solar and backup diesel generators.

The common AC generators, with 5 KW power are very hard to run at a set frequency and to synchronize. A 1 ton flywheel will help as it will be a rotary speed sink you could slowly adjust the other one to. The problem is these generators adapt to changing load with a throttle loop that is 1-2 seconds lone. By that time your generators will have shorted out and popped their breakers. 1/120 sec out of phase = dead short between them

I thought an inductance motor used as a generator will automatically synch with the primary supply on a system. I could be wrong. I know that this is a way to send juice back into the grid. I am pretty sure this is how the hydro-generators work.

chris

In Ac machines lab we used to operate two generators amd connect bulbs between the phases of each machine and slowly adjust the speed until your bulbs went dark, which means no phase difference. If you were one hertz out you would get a bright dark flashing of 1/2 second and you gradually bring them together and connect them together in a dark moment. At that time they tend to run in lockstep, but you must watch the circulating currents as the slower one get run as a motor by the faster one, which is why they synchronize. Too high a circulating current and it falls from synch and all the breakers start banging. These were foot pedal breakers at 500 amps.

This was in 1960 with old machines. Now it is all electronic and much better run

Your second motor is and AC inductance motor and you want to build a generator set with it?

Good luck, it will never work as an inductance motor can't be used as generator.

I think it would be better to plan your electricity usage through a priority system: if you are cooking, the washing does not function,...

What you also can do is couple the heat of the engine to a boiler, not having to use the electricity to heat up your water used in appliances. (combined with the exhaust you could make steam, which can be used in other processes (steam cooking,..) Try to be inventive in this things.

You can easily couple two generators, you only need to synchronize the output. There are specialised firms that can make automated drivers to do this. There has been a blog on this item some weeks ago: http://cr4.globalspec.com/thread/5605

Gwen

I've operated generators in parallel in nuclear power plants and have brought diesel gen sets on line and paralleled with steam turbines in the past. I now own a wind turbine manufacturing plant. One commentator is correct the sycnchronious machine will lock in provided the prime movers are within band. The problem you will have is that both these machines are relatively small. Small gen sets are notoriously unstable (speed control of the prime movers) I agree with several comments I saw.... split the bus or use a rectifier and inverter array. This is how we interface a lot of the small turbines (20 kW and down) that we manufacture. Many systems we design utilize DC storage devices and it makes it much simplier to interface with multi input hybrid supply systems. We can easily use either a phased transformer or PWM inverter to provide regulated outputs. Highly variable outputs can wreak havoc on your loads severly limiting their life span.

Comments posted by many respondents have stated that in priinciple, you can do what you want, but you need to be VERY careful and VERY wary of potential hazards. Aurizon was correct in stating that light bulbs can be used for synchronization before closing the breaker for the "induction" generator. Customarily, a so-called synchroscope is used for the same purpose and is a little less ambiguous than looking for extinguishing of lamp filaments. It is essentially a wound rotor motor, comprised of a three phase rotor and three phase stator, each connected to one generator if your system is three phase (if not, a set of differentially connected 60 Hz selsyns with a shaft pointer on the differential one will serve the same purpose). Either scheme produces shaft and pointer rotation in step with frequency and phase differences between generators. A three phase synchroscope is for sale on ebay, at http://cgi.ebay.com/Vintage-Westinghouse-Synchroscope_W0QQitemZ230104436783QQcategoryZ73159QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

If you REALLY want to do this without resorting to AC-DC-AC conversion, you will need to CRITICALLY obey the following conditions:

1. An induction motor will serve as a generator when run slightly above synchronous speed. However, your 28 HP generator will need to serve as the frequency determination "master".

2. You must modify the governor on your 20 HP engine to produce significant speed droop under load, such that the engine cannot forcibly run the motor at a fixed or nearly fixed speed. Constant torque with a speed limit of perhaps 7% above applicable speed is what you want.

3. Begin with the 28 HP machine in operation. Start the 20 HP engine, and bring the speed up to synchronize the two as described by Aurizon or by means of a synchroscope. Then close the circuit breaker for the 20 HP machine.

3. Meter the 28 HP generator output current, and bring up the 20 HP machine throttle opening to share maybe half the load. Beware that if you reduce the load, the 20 HP machine may "take over" the system for a fraction of a second, raising the frequency and voltage. It will back drive the 28 HP machine and speed up the engine despite the fact that the governor on the 28 HP machine has already closed the throttle. However, the 28 HP generator voltage regulator will reduce its output. In turn, that will cause the 20 HP machine to cease generation, because electrical output from an induction motor cannot be self-sustaining unless connected to another "infinite bus" source of power. You may find the combination to be unstable for that reason, in addition to reasons covered below.

4. Be very careful to not vary the load under conditions where both sources are working. As pointed out in other postings, control dynamics of generators feeding infinite busses (your 28 HP machine) can be complex and potentially unstable under some conditions. If you are familar with control theory, you can consider several factors as causing poles above unity gain when the loop is closed, including interaction between torque stiffness of each machine, response time of each (including angular inertia effects, governor latency of the 28 HP machine, and possible negative resistance of loads with power factor corrected power supplies).

5. If you use light bulbs for synchronization, they may need to be at least 100W each to provide excitation for the induction motor. If you use a synchroscope, use light bulbs in parallel for the same reason. Generating stations often have (had?) both.

Good luck.

BernieK

Thanks, You have beenmost helpful.

a couple of questions.

1. I have not yet assembled the 20 HP baldor 3 ph motor to a gen set . I will be using a 6HP (lister 650 Rpm) DIESEL to drive the Baldor, so I don't beleive I will have a problem of overdriving it too much.

2. How do I make the connection to attch on or more legs of a 3 phase to a single phase primary grid (the 28HP setup is driving a 15kw 110/230V ST15 Head). Can I use only one leg? or am I able to use 2? I really don't want to go through the gyrations of an inverter, synchroniser etc...

3. I have successfully synced a single phase 1/2 HP to it with no difficulties, though I was able to overdrive the 1/2 HP (read SMOKE) with the 6HP diesel setup. I did this by disconnecting the starting circuit and capacitator and using only the run windings. My question is what happens to the other 2 legs of a three phase motor used in the same way?

4. If I am able to only use one leg,l will my sync speed be higher than the original 3600? Then if I am able to use 2 legs , ditto?

thanks,

Steve

This message is in reply to biloxibad, message number 15:

Firstly, all of the parallel connection caveats originally stated remain true.

1. You can connect one leg of the three phase motor to your "grid" if the motor gives you access to the neutral connection internally, on the premise that the motor is WYE wound. If it is WYE, and the neutral is not brought out you can usually disassemble the motor, gain access to the neutral splice, and bring out a lead. That will give you 115V assuming the motor windings are connected for operation on 200/208V between phases.

2. You can attempt to connect another phase of the motor to the other side of your single phase 230V system, but you must remember that the phase angle in a three phase system is 120 degrees, not 180 as in single phase 230V with a neutral supplied for utilization of 115V on each side. That is the reason that phase to phase voltage in a three phase motor is 200-208V, not 230-240V despite the fact that phase to neutral voltage will be 115-120V. Thus, the motor will need to try to generate 230V from each phase connection to the neutral to try to feed your system. The stator iron may saturate before that condition is reached. Moreover, circulating currents will exist between your two systems because of the phase angle difference. It may be possible to have the motor rewound for 120/240V single phase operation (without the starting winding) but that is expensive. You may be able to find a single phase motor of that type, but they are rarely made above 5 to 10 horsepower.

3. The driving speed of the motor will be a little above synchronous. If the stator iron does not saturate, you will need to drive it a percent or two faster than if the motor were single phase. A big single phase motor is a much better alternative, although as previously stated, you really need to know what you are doing, and you must be aware of the possibility of instabilities arising.

BernieK

Just remember, instabilty can be extreme

http://rhysy.plexersoft.com/Explosion%20test%202e.jpg

:)

This reply is to message 19 posted by Aurizon:

You are absolutely right about instabilities. Having spent the first 20 years of a 42 year career in process and energies instrumentation, I've been at several large power plant startups, watching with a fast beating heart as the operator closes the breaker to put a multi-hundred megawatt unit on line. You watch with anticipation as the synchroscope revolves about one revolution in 2-4 seconds in the "faster" direction, and when the breaker closes, you watch the "phase rock" which dies out in about 5 cycles, each lasting about 1 second in period. The first excursions of the underdamped phase rock are each hundreds of megawatts, drawn from and contributing to the grid, all arising from combination of the spring-mass-like effect of incredible torque stiffness and monsterously high angular inertia of the unit coming on line to the grid (at that time the governor is out of the picture and steam chest valving was controlled manually, at least back then). Only after that is the governor brought into play, configured with load resetting speed. It is quite a sight to watch.

Feeding a less stable "infinite bus" which constitutes a considerable fraction of the load coming on line will be frought with more problems due to interaction. To complicate matters further, an induction motor is not self generating. It will add to power already fed to it so as mentioned in my previous postings, instabilites are compounded yet further. The probably worst scenario is the induction motor tending to take over the system, power contribution from the "master" falling away as its voltage regulator cuts output followed by collapse of the armature magnetic field remnant in the motor rotor. Thereafter the cycle repeats.

The original poster's intent CAN be implmemented, but only with the utmost of care an attention to the most subtle of beginnings of instability as previously stated.

BernieK

Hi we are running a 150kW (201hp) diesel generator on straight vegetable oil parallel to the grid. We would like to add a second but I know I wouldn't want to just rig that myself as I have never done such a thing and am also not insured for such a case if a mishap happens ! 150kW might just be enough juice to kill a person and ruin someones day.

But I sure would be interested in the wood gas you are using. Do you produce it your self. If so could you provide some details of your operation.

Good luck with your project.

Man, that's gotta be one heck of a lot of Mazola you feed that monster!

I'm very interested in this setup as well, as we'd like to go off-the-grid at some point within the next few years.

-e

The wood/gas dual fuel system characteristics determine the recommendation. Perhaps you can be more elaborate with the available fuel supply and control thereof. For certain, wood gas dual fuel is not a quickly responding combustion system as compared to the load of an arc welder, hair dryer, 240 v cooker, or coffee pot. A full time operator is apparently not available for the generator and combustor and, if so, his professional attention is divided elsewhere.

Reasonably, as always, designate the load of each specific circuit to prevent overload of available supply. Depending on available funds as compared to convenience, use a three way breaker or manual throw switch to switch select circuits to the redundant or backup supply.

If you gotta ask how to synchronize supplies, drop the idea. Do not attempt to duplicate or replicate this at home. Synchronization of two small power supplies will not safely happen with acceptable reliability. If it were to happen, those involved will regret that it did or die trying. No pun intended.

The controls are all to simple..

Start it on Diesel, Stabilize it on diesel to the RPM (HZ) required, takes about 1/2 hour running to allow genset to heat up whicn on the ST head means I need to filddle with the AVR rheostat to keep voltage at 230 as the windings heat up we lose some capacity.

Once ready, apply woodgas to the intake, You will hear no difference, but will be able to see the injector rack backing down, injecting less and less diesel as more and more woodgas is input to the intake.. The RPM and HZ , voltage, remain constant, as the diesel takes the role of ignition source for the woodgas and takes up any slack in woodgas delivery to keep the operation constant.

If woodgas delivery slows as in the wee hours of the morning when the fuel charge in the hopper becomes depleted , the diesel rack adances to take up the slack so that the power remains constant.

It is WAY too simple..

I am taking some pictures to post so ya can see it!

Best regards

Steve

Those of us in the power generation business will tell you "we" could parallel these with minimum instruments, and in short order, electrically. But without sophisticated engine governors with droop adjustments they will not equally share load in proportion to each engine size. So, to avoid a mishap, don't try it even if you catch the 'how to' from posts here. You must understand the concept and what to 'listen' for when trying this. The most complex part of synchronising can be explained with a rather long instruction, but then you will have a double long post regarding engine governor response and load sharing and how to adjust the governors only to find out the governors cannot be adjusted and each engine's load response so different that one will be at 50% load and another 120%. You can hire a local generator set company to advise you, preferably from an internationally known company.

George

The mini wind generators beloved by the 'greens' are supposed to feed power back to the grid when you don't need it, I believe they do this by converting to DC and the using an electronic converter to convert to grid frequency with the appropriate phase lead.

A ridiculously complex, expensive and inefficient process all with the hope of 'saving the planet'

Here is how it is done.. Bertha is a 28 hp 2200RPM chinese diesel motor head. It is the prime mover for the system belt driving a ST15 genhead. This system is capable of a constant 56 amp 230 volt load with starting capacity to 88 amp. It is extremely stable under load.

The gasgen set is a home brew setup converting chips and small wood blocks via pyrolisis in a controlled air inled system through a downdraft gassifier. The gas (smoke) is sent through a cyclonic cleaner which removes the solid particles , (again home brewed from a 55 gallon drum) from there it is cooled and vapor condensed, and dry fiberglass filtered before going to the going through the air filter intake of the prime mover.. A butter fly mixing valve staticaly mixes the intake air with the woodgas in an approximate 50/50 ratio. Note the intake vacuum pulls the woodgas through the entire woodgas gen system.

In Operation I bring the diesel online and set the frequency under load at 60hz 230V with straight diesel. Once stabilized with diesel, the wood gas is introduced, this increased fuel load causes the engine to attempt to speed resulting in the the diesel injection rack to close, keeping the constant RPM and current stable. The diesel injection is only acting as a pilot to begin combustion of the wood gas, and as a govenor to keep the current steady.

Economies are: diesel is reduced to about 10-15% of normal consumption, wood is burned at a rate of about 26 Lbs/ hr under full load, meaning a hopper of 100+ Lbs lasts from 4 - 8 hours.

Very Stable curent, very reliable operation,

Down side is that I have to keep physically fit chopping wood, running it through the chipper and chunking it to usable size.. It takes about 20 minutes a day to clean out the ash, refill the hopper. The coals rarely go out so it self starts once the new fuel is loaded. This all happend while the diesel is chugging along as it does'nt care if it's air is from out side or has been channeled through the woodgas gen.

Now back to my original question, I need about 8kw additional power during peaks..

To do this I have a Metro 6/1 (Lister clone) 650 rpm diesel, with 300 lbs flywhel weight to drive a second generator head.. In the scrap pile is a 360 RPM baldor 20HP, 3 phase motor.. How do I connect it in times of peak to my primary set-up. Can I use one or 2 legs to make 230 by overdriving the Baldor so that it begins generating, I read somewher that it will sync and follow "the lead" of my prime system. Just need to know the theory of the process..

Thanks again, and I will go take some pictures and share what I am doing.

Steve

Don't weld while washing :-)

But if you wash a big part of your electricity consumption (usually about 4kW) is used for heating the water. Why not heat the water from the washing machine with the cooling system of the diesel generator?

Think of installing a big tank that you use for hot water storage (for showering, washing, washing the dishes, heating your house in the winter etc) eventually complemented with a heat pump.

Cooking: the same picture : use the 90°C cooling water temperature to heat your water in which you cook the vegetables. Use a high pressure cooking pan and the boiling of the vegetables will only take 8-10 minutes and cost you little extra energy. Do not heat more than needed. It is not the amount of vapor that you produce that will cook your vegetables but the temperature of the steam)

Drying : use the exhaust heat of the diesel engine. Extend the exhaust (you can do that by welding some additional tubes together) and put that extension in a ventilated room. Your laundry will dry in a few minutes for free and without putting load on your generator.

In an extreme way you can also cook on your exhaust manifold system. There is enough temperature and some guy from America even published a book about it called "Manifold destiny".

Some very simple tricks that increase the total efficiency of your energy system. And I guess it must be fun to install and test all that.

These are all great ideas, and I will be doing some or all of them over the next couple of years, But as we all know the number one priority is to keep the BOSS happy.. If she ain't happy , no one is happy.

That being said, she freaked when I said that< enough was enough > and then withoug ceremony pulled the plug on the power utility..

I have to maintain HER status Quo, whilst beginning the economies of a CHP system. I am disabled and move very slowly so take much longer to do things than most.

while I can do these things, The one thing I can do the quickest is to add generating capacity, which i intend to drive with my 6/1 6HP lister until the changfa 1110 comes in, I aLready have all the components, just need to be able to hook up a leg of the 20 hp Baldor setup to my existing Prime Generating system..The most I will be able to drive from the 6hp Lister type will be about 5KW so I don't beleive that it will be driving the "mini GRID" with it's small output, only augmenting it..

SOme of my future plans are:

1. Using the exhaust of the Prime Mover through a "gas water heater" to make hot water. (maybe get a Hot tub and heat it too? )

2. DIverting the engine cooling through a heat exchanger/radiator in the Central heat system for capturing engine heat to warm the house..

3. I myself am ready to go to alternate cooking methods, But the BOSS ain;t going to give up her electric stove and oven.. sooo

1. I have not yet assembled the 20 HP baldor 3 ph motor to a gen set . I will be using a 6HP (lister 650 Rpm) DIESEL to drive the Baldor, until my changfa 1110 comes in, so I don't beleive I will have a problem of overdriving it too much.

2. How do I make the connection to attch on or more legs of a 3 phase to a single phase primary grid (the 28HP setup is driving a 15kw 110/230V ST15 Head). Can I use only one leg? or am I able to use 2? I really don't want to go through the gyrations of an inverter, synchroniser etc...

3. I have successfully synced a single phase 1/2 HP to it with no difficulties, though I was able to overdrive the 1/2 HP (read SMOKE) with the 6HP diesel setup. I did this by disconnecting the starting circuit and capacitator and using only the run windings. My question is what happens to the other 2 legs of a three phase motor used in the same way?

4. If I am able to only use one leg,l will my sync speed be higher than the original 3600? Then if I am able to use 2 legs fom the 3 phase Baldor, ditto?

BTW this community is great, all seem ready to help without criticism.. You don't know how much that is appreciated.

steve

Mother Earth News had a really good article on the system you are developing. They used a 2300cc Pinto motor as the prime mover, a used motor as the generator, the engine cooling water heated the hot water system, and the exhaust system transfered heat into the heating ducts. You might go into their archives for the article. About 10 years back, I think.

Found it , Thanks!

I do not think you are getting it! Running (rather trying to run) 2 small generator in parallel on a home electrical grid is suicidal!! The load shifts significantly instantaneously. The engine governors are very slow in comparison, and the two different gen-sets will have vastly different control characteristics.

As example--say running at 130% of the larger unit, with fuel rates adjusted such that the larger unit is now @ 80% capacity, smaller unit will have 26% of total load, which is say 80% of its capacity. (somehow got there) Now a big load (electric water heater @5KW, 30% of total load) drops off. The gen-sets will accelerate until the individual governors reduce fuel rate. Without careful analysis of the inertia and torque characteristics, it is not possible to predict which unit will try to accelerate faster. The units will try and stay synchronized--and very large currents flowing between the generators can (WILL) develop almost instantly to provide the 'accelerating/restraining' torque. The magnitude of this current is limited only by the current carrying capacity of the wiring connecting them--as a DIRECT SHORT @300V EQUIVALENT results just at the 'break synchronization' point.

As you describe the proposed system, the smaller driver has a very heavy flywheel, which will probably cause that unit to lag the other in speed changes (either up or down). This GUARANTEES you will have major instability and cross current flows during any load change.

The ONLY way to try it is to MECHANICALLY lock the 2 generator shafts together, guaranteeing 'in-phase' operation.

Please do not try and make it work--you can't, nor can anyone. Elephants just can't fly. If you have ever witnessed a high current short and resulting explosion-you would understand the danger. When the conductor melts, it vaporizes with explosive force, usually destroying the industrial switch cabinet enclosure. Just like a bomb.

the answer to your prob is way to simple.... remove/isolate the garage load ,except for the overhead lighting from the house panel and the use your second gen set to power the garage as needed..... the boss is happy with all her toys and conveniences in the house and you are happy in the shop And most importantly you get to reap the benefits of happy wife.... lol

Keith is correct.

Mechanically tie the two shafts together ie a flexible universal joint. When there is need for extra power cut to no fuel with the second in mode "free wheel"

Get a microwave for cooking. Ditch the 240V cooker.

Youse see what we have here is a social concern rather than a technical problem. When either you or the wife are "home alone", only the primary power is needed. Electrical circuits for that use go on the breakers fed by the primary generator.

When you are home alone, alls you need to run is the circuit with the cooker, washer, and dryer.

When the wife is home alone, alls on the circuit in use is the welder.

Use the big generator to drive the circuits for the wife to use.

Use the redundant generator for circuits when both are home together and alls running simultaneously.

The flywheel governor controls the 60 Hz for the primary circuit. The mechanical flexible universal controls the second generator and keeps both in sync at 60 Hz. When the speed drops below 60Hz, the governor of the redundant backup generator feeds fuel to the backup power ONLY if the first or primary generator is at full throttle.

To make the boss happy, I would begin to add a solar panel ($500) and battery ($100) with inverter ($40) and backup battery charger ($50). Predictable small energy usage could gradually be transferred to that circuit. On the solar circuit, use microwave to cook (6 amps/ 60 secs), refig (6 amps/ 1hr/da), HP LED lighting (5-10 watts per light continuous) and corn stove heat (100 watts continuous) from the solar system. With solar circuits in service, there may be days when you feel like staying late between the sheets. Use the light from corn stove flames to keep the solar panels energized 24/7 globally use low cost locally renewable whole kernel shelled corn energy functions properly and predictably when the sun doesn't shine, the grid fails, and the joints are frail. PS: A corn fed "T" bone grill cooked on open air corn flames has a unique sweet corn flavour. USE ONLY cast iron grille or 316L SS materials with corn flames. To share & read similiar experiences worldwide, send messages to www.groups.yahoo.com/group/cornstoves

WOOHOO!, it works like a champ! the Lister diesel cranks the 20 Hp Baldor insync with the ST15.. have 78 amps total showing right now at 230 v 60 HZ . Both motors blowing black smoke..

The trick is to set the "slave" (smaller engine/gen combo) at a maximum setting overdriving the electric motor, In this case I limited it's output at 2700 watts. This de-throttles the main mover while allowing them to remain in sync..Basically I am producing a set amount of current with the smaller engine, while the Prime Mover does the balancing. I can apply different loads with no change to the small engine/Gen output , The output of the Prime Mover varies. I get just a bit of harmonic between the 2 of them when I decrease the load to near zero. This settles out in 2-3 seconds. This only shows up below 3kw. Above that the smaller one keeps cranking while the prime mover loafs. when the load is increased to 4kw+ the prime mover begins to kick in producing more and more of the current.

to reiterate the setup

Bertha=28Hp 220rpm diesel powering a 15kw single phase

Bert=6 HP lister powering a 20Hp 3600rpm 20 Hp 3 phase Baldor. One leg attached.

Now to build a manifold to supply woodgas to both of them simultaneous.

Cheers and thanks to all who contributed.

This can work well until the 'event' occurs.

Why do you only have one leg attached on Bert?

Rewire the main panel in your house, to a full 3f system and have the full capacity of Bert, which triples the power you have from one generator.

Normally welders have the possibility to go for 3f. So have other big consumers. At least on this side of the ocean it is like that.

Gwen, I could do that.. but my primary genset Bertha is a single phase.. HMMM mebe I could change over the GenHeads and let Bertha drive the 3ph Baldor., How would I excite it to start current flowing?