Diesel Engine with an Induction Generator?

I wish to generate about 1kW of 230v 50HZ electricity, with a grid connected generator, driven by a diesel engine (Biofuel/Transformer Oil??).

An induction generator could be the easiest way to do this, however some form of clutch mechanism will probably be required between the prime mover and the induction motor.

Are there easier ways to do this?

Any assistance with this project would be appreciated.

Ross

Normally, the generator is coupled directly to the engine and there is a goverenor control to regulate the speed (frequency) of the generator. Voltage is a result of how the generator is wired.

For 1 KW you may want to look at a different route as the generator will not be cheap (if you can find one that small) and you need some good control to keep your frequency correct.

Why not just mount several Car 12 volt alternators on a small diesel, have them charging some car batteries and use a converter to make the AC at the voltage and frequency of your choice. I bought a 1 KW 220v 50 Hz converter for €120,- recently........! It works just great.......flattens batteries quickly though!! The diesel engine will help just fine....!

Not a bad idea! I have one set up with a small 2-stroke cycle gasoline engine. It works fine and has been working fine for about 18 years. I'd consider changing the engine to diesel if I could find a small one (3 to 5 hp) for a decent price. But, that would make the entire assembly weigh a lot more than it does now. I use a 12 ah motorcycle style battery (AGM) between the alternator and the inverter. This unit also doubles as a automobile battery charger.

Induction generator is basically a induction motor driven above synchronous speed.If u have a motor at 1500 RPM (4p) then if u couple to an engine and run it above 1500 rpm it will start generating.Pl refer to Fitzerald and Kingsley for theory.It is commonly used on wind mills .u don't need any clutch.

......and that would be at the frequency of the normal supply either 50 or 60 Hz?

I don't think so......!

Thanks for the comment.. Induction generator are commonly used for micro hydro as well as other applications.

I have visions of starting the induction motor electrically and having it running at approx 1500 rpm (4 pole motor at 50 HZ), then start the diesel engine, and speed it up to a point where it is able to mechanically "drive" the induction motor at greater than no load speed and thus generate electricity. I am wondering whether I need a clutch between the engine and induction motor, because at some stage I will have the induction motor sitting unloaded at ~1500rpm less a bit of slip, and the diesel engine at maybe only 1000 rpm, and speeding up.

How do I overcome this problem? I would prefer to do this all at 50Hz 230v, rather than utilise batteries and inverters etc.

Thanks

Raspberry

Or do I just wind up the diesel to about 1600 rpm, and then close in the circuit breaker on an induction motor which just happens to be connected to the output shaft of the diesel?

R

If I understood you correctly, you feel that an induction motor (1PH or 3PH?), when turned by a prime mover (diesel engine) will make electricity for you.

This may or may not produce electricity, but if it does, its only because the motor rotor poles have become magnetised over time, what voltage it will push out is anyones guess and if I remember my lecturer correctly (its a long time ago) the magnetism will eventually die away and you will have no output....also you will have no control over the voltage, which is needed!

An induction motor rotor has no physical windings that you can see, its often called a "squirrel cage", this rotor "follows" the stator as each stator pole is magnetised in turn. There is usually a small amount of "slip", 5 % comes to mind.....

To make AC, you need to have a way of making the Rotor Magnetic, it was usually done with a small DC generator, mounted on the same shaft, that supplied a variable voltage, though the shaft to the rotor windings.

Why variable? simply so that you could control the voltage output of the AC generator as the speed of turning is a non variable, due to the frequency requirements of where you actually live.

Unless the physics of modern AC power generation have made some vast changes to what I have written above, do not expect your idea to work!

There of course, trying it out will a) Give you some important physical knowledge and b) Get you up to speed with the mechanical side, so it is not completely useless.....

What I initially suggested using 12volt generator(s) and an electronic DC to AC converter etc, was I believe the best idea for such a small power requirement, I still think that.......it would be the way I would go. Also, you could add extra converters if ever needed with little problem....

If you want to progress your method, you need to strip down the rotor and change it to either two fields or three depending upon 1 phase output or three. These fields need to be supplied with an auto controllable DC source (either on the same shaft or via slip rings), using the final voltage output of the generator to supply the feedback. Hand control is only workable with a completely static load. Industry generators are built generally speaking with a 45% droop characteristic from no to full load.

Generally AC generators are built with a strong "droop" characteristic for the reasons of control and parallelism, but if you are up to the development, the distance between the rotor and the stator actually sets the droop characteristic if I remember correctly, therefore theoretically, you could build a generator with either a very minor droop or none at all.....I have never done it, so I cannot help you further.....but that would obviate the need for control per se.

I would suggest that you study the way power is generated as what I have written, may be completely out of date, but I still feel most strongly that your induction motor idea will not work as you desire....sorry.

Your wanting to try this, leads me to believe that you have little knowledge in this area, please do not forget that there are many places where you can either get killed or badly injured if you are not FULLY aware of what you are doing. Even professionals are dying every year through some small mistake.....

Hello Andy

Thanks for the comments. I am registered in New Zealand as an electrician, although this generation is new to me.

I am lead to believe that if a mains connected, squirrel cage induction motor is turned at speeds higher than its normal no load rotational speed, then it will convert from a motor, into an AC generator. The beauty of this concept is that no synchronising is required.

This theory is often used in micro hydro systems. The generator is run up to speed (as a motor) and then the water is turned onto the pelton wheel or similar connected to the rotor, and the force of the water tries to run the motor at speeds higher than sync speed. This will not happen of course, but the net result is electricity generation, at mains voltages and frequency. Really simple apparently..

Assuming it works I need to connect the induction motor to a combustion engine, and I assume the induction motor cannot mechanically rotate the operational diesel. How do we sync them??

R

You do not need to sync them, if you want to try it out, just connect the motor to the engine and start the engine, then check your voltage and frequency.

The frequency will be off completely if you turn it faster than its rated speed.....

What voltage you get and for how long, only you will be able to tell us!!

Best wishes, experimenters must experiment.

I am interested in the results you achieve whatever they are.....as are many others here.

And the plot thickens.......................... Just what is the real goal here? Sounds like you want to sell power back to the power company or buck your current draw. At 1kw, you can't economically produce it from a diesel prime mover unless you are getting your fuel really cheap (almost free). I couldn't do it at the 200kw level a few years ago when I could buy #2 diesel at .28 USD. Now, if you were talking wind or water power as the prime mover, there may be hope. But wait! We haven't addressed the capital expenditure amortization over the life of the equipment. Oh s@!?!!!, This isn't feasible no matter how you look at it.

You are of course right, but a lot of people need to try stuff out for themselves and I have to admit, I am interested in the results.

I was taught the theory about 43 years ago, now someone wants to try the practical way, just let him!

I have access to thousands of litres of used transformer oil that the owner is currently paying to get taken away.

Also want to have a play!

R

Go get 'em!!! Best of luck. I have played with using waste oil for about 30 years. I blend 35% with #2 fuel oil for home heating and 15% with diesel fuel for my 2 diesel autos. In the heart of the winter, I don't run blended fuel in the autos because of the gelling potential. Back to the subject - I too would like to hear how you make out with this project. Cheers!

I have the feeling, that you have little idea, nor the engineering background, for this project, which is why you have come correctly to CR4....(please state your qualifications, so that we do not talk down to you in that area, or at least not so that it shows!!)

But we need exact infos as you understand it....please therefore comment on each of the following points and add anything else that you feel might be relevant.

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1) I am guessing here, but assuming you are in the USA, then you probably need 110 volts at 60 Hz, or if somewhere else, 230 volts at 50 Hz, am I correct, if so, which one is correct?

1a) Or are you after 3 phase power? 230 volts Phase to Phase (USA) 60 Hz or 380 volts phase to phase (the rest) 50 Hz?

2) Some oils (lubrication and hydraulic oils for example) will not burn so easily without heating them first or additives (or both!), you need to get your diesel motor running properly on this oil, before you even think about attaching a generator to it.....the reasons are that some oils are designed NOT to oxidize when in use, which is like saying, not to burn easily.....I feel that it is highly possible (I am no expert on oils for transformers) that it would be designed NOT to burn easily.

3) Have you understood that an induction motor is not an AC Generator, without a lot of fairly major engineering changes, that I find personally, totally impractical?

4) Car or Truck alternators, produce AC, which is usually rectified (internally) to produce about 14.4 volts DC (Trucks about 25 volts DC).

5) Some of these car alternators can be fairly powerful, for example, some VW TD-I Alternators produce about 1.7Kw of power, because of the way the engine has to be quickly warmed up when fully cold......and some truck alternators will produce a lot more than that!!!

.......but what we really need right now are some hard basic facts or statements, from you about what you would like to do.......so that we can help you fully.....or just forget the whole thing please.....

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We need a statement from you like:- (please use my statement with your additions and changes if that helps you to help us!)

I want to use old transformer cooling oil to run a small diesel engine, to produce 230 volts AC 50 Hz at around 1 KW for running my fridge, freezer and the central heating pump if power fails to my house in wintertime. (remember that 1KW will not do very much!!).

Q1) What do I need to attach to my diesel engine (type and BHP) to achieve this aim of mine?

Q2) How must the oil be changed (or not!) to allow it to burn easily in such a motor?

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I actually feel, that to get such oil to burn in a diesel motor may prove to be the worst problem of all!, and that a steam boiler and steam engine (or a large Stirling motor!) might be a better way to go!!! But I could be completely wrong on that score......

Thanks in advance for your full understanding and help in this matter.

In reply to 17:

I am licensed power plant operator and instructor of operational fundamentals. I have followed what you have siad so far to this inquiring individual.

What is it about automotive alternators that make them inductive in nature? I understand they are manufactured and supplied with voltage regulation and that frequency is of little consequence since the AC is converted to DC. Unlike snchronous machines however they have no slip rings or induced excitation voltage supplied to the rotor. They simply turn and output electrical power which this person is looking to do. What allows them to do this without exciter volage and current? Can this type of alternator be better controled and utilized in our grid based 60/50 hz world? - without the added inefficiencies of lead acid and power conversion?

Generally speaking, automobile alternators have excitation current applied to their rotors through slip rings by a built-in solid state voltage regulator that gets its operating signal voltage using a separate wire attached to the positive pole as close to the vehicle battery as possible. Another signal is provided through the ignition switch to turn the excitation current on or off. The actual excitation current is provided to the regulator from the alternator's output connection which is connected to the positive pole of the battery and isolated internally from the stator windings by diodes.

you may want to read what this fellow has to say about the subject:

http://www.microhydropower.com/staffpubs/staff4.htm

Andy

Thanks for your posts. I am looking for a 230v/400v 50Hz output from a grid connected induction generator, which of course would have to be three phase. I am registered in New Zealand as an electrician and have worked in the electricity supply industry for about 25 years. Currently working as a technician in metering systems, HV protection, and communications.

A standard 3 phase squirrel cage induction will rotate at about sync speed unloaded. If however one "grabs" the rotor and attempts to rotate it at faster than sync speed, then the motor will turn into a generator. No fancy control systems are required. Given that the motor is connected to the grid, it will not rotate faster than grid frequency, but electricity is generated at grid frequency and voltage. This is an asynchronous generator.

My original posting related to the mechanical interconnection between the diesel motor and the generator. I can see there being problems with firing up the diesel and starting the electric motor on the same shaft at the same time, when the motor is at 1500 rpm and the diesel at maybe only 500 rpm and accelerating. I think I need a clutch or torque converter of some sort.

An easier option would be using batteries and a grid tie inverter, but I would prefer to direct connect to the grid, without the losses and costs of alternators, inverters and batteries.

This project is intended to be experimental, but generate a few kWh at the same time, and use some surplus fuel.

Thanks

Raspberry

I'm not an EE, but I am an investor with an idea. I was hoping to add some information in and ask a few questions. I'm growing frustrated trying to find information on grid tied induction generators. Please do not assume that just because this plan is not feasible in your area, it is not in others. Every thread on every forum on the internet I read is absolutely littered with the 'this isnt economically feasible give up now' posts. Is it possible to pass around information instead of nay saying?

My Economic Feasibility:

My cost for WVO = free

grid rate of electricity (this is what they said they'd pay me) = 3 Philippine pesos per kw (0.07USD at current exchange rates)

cost of collection and processing = 10 pesos per gallon (0.25).. (Actually, there is no cost at all since im planning on running pure unprocessed WVO and have 2 guys on bicycles paid minimally to pick up all the WVO, I just thought I would throw this in 10P figure in here just to be safe.)

Fuel consumption for generator = 1.25gph @ 25kw

net income = 62.5P/hour (1.5$/h - 35$/day - 12500$/yr in USD)

Maint. = 60$/mo for full time mechanic/EE (again, its the philippines jobs pay 50-200$/mo on average) + cost of replacement parts, oil changes, fuel/oil filters, 200$/mo or so (Assuming i change fuel/oil filters once every 100-200 hours))

profit = 9250$USD/yr (365,000 philippine pesos per year)

Cost of genset = 500$-1000$

ROI: 1.5-2 Months

My questions, Has anyone actually done this? What kind of protection in the form of power relays/breaks/circuits do I need? How 'dangerous' is this (is there a risk (with a properly installed system) of blowing generators/diodes/fuses, etc?)? What kind of clutch/gear mechanisms are needed if any? (going back to the original posters question)

From what i've been reading here and else where, all I need to do is rip out the capacitors from the back of any AC generator. This 'turns it into an induction generator because it cant create a magnetic field' (or something like that, remember I'm not an EE. I'm just trying to gather the information necessary to take this to a real EE locally). UL Listing does not matter, I'm not in the US. Take the gen set, plug it into a wall outlet, let the generator rev up and sync to grid, kick on the diesel generator with WVO and hope it runs at a slightly faster RPM to produce power? (i know it cant be this easy)

My hope was to start off with a 5kw 'test' generator. After it has proven reliable for a few months, then upgrade to a 100kw or 250kw power plant.

Any information/help is most appreciated

Philippine grid information:

Pole to house is single phase 240v 50hz (they use a single transformer for multiple houses).. I'm unsure of what the grid beyond that is rated at, asking about it before, they said they'd provide me with my own transformer if I purchased it. Unsure if this effects anything at all. I think beyond the transformer its 3 phase 10kv @ 50hz. I didn't inquire a lot about the grid beyond my house... at the time I was speaking to the engineers from the power co... so this is all the real useful info I can provide.

I just checked my meter to be sure and it's actually 240v 60hz single phase.

thanks again for any info that can be provided