Generating experiments

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domy
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Generating experiments




by domy » 09/08/17, 18:32

Hello
I found this on the internet "alternator conversion of a small engine" and would like
The experienced but I miss some details.
Electrolytic capacitors are needed but in 12v I did not find what to replace them with?
And must it be polarized or not?
With regard to capacitors in parallel paper or oil, I suppose that they are capacitors
Permanent? And must it be polarized or not? They too, if someone could inform me it will be nice
Thank you in advance for your answers and clarifications
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izentrop
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Re: generating experimentation




by izentrop » 09/08/17, 22:00

Hello,
It must dated your scheme because the paper capacitors date it.
Not all engines can run as a generator and those that are compatible make very bad generators. What is the engine you want to convert?
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Re: generating experimentation




by domy » 10/08/17, 11:01

Thank you for your answer
here is the motor plate concerned
IMG_9602.JPG
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Re: generating experimentation




by chatelot16 » 10/08/17, 15:26

the electrochemical capacitor priming system is doubtful ... there is more simple: connect the engine to a battery 12v stopped and it must be magnetized enough to start alone when it turns

the capacitor plays the role of exitation: if the capacitor is too weak it does not start, if the capacitor is too big the voltage goes up to saturation, with waste of energy ... if we are lucky it saturates at about 220v and we are happy ... if the engine is of high quality it saturates at a voltage too strong

to do well it would take a variable capacitor controlled by a regulator

in three-phase it is not essential to use a real capacitor: a three-phase inverter can become equivalent to a capacitor, and even a variable capacitor, so make a good voltage regulation without loss of energy by saturation: there are big alternator working according to this principle

there is a small generator whose alternator looks like a single-phase motor, with an aluminum-molded rotor like a single-phase motor: it works well but I imagine that the design of the engine is special: saturantion of the rotor before saturation of the stator: in case of saturation of the rotor it does not waste energy because it is of the very low frequency ... in case of saturation of the stator it is catastrophic for the yield
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Re: generating experimentation




by izentrop » 11/08/17, 00:38

domy wrote:Thank you for your answer
here is the motor plate concerned
IMG_9602.JPG
It is a three-phase asynchronous motor (it shows at its rotation speed). Due to its principle of operation, it can not be converted into an alternator unless the squirrel cage rotor is replaced by a permanent magnet inductor or by a wound and powered inductor like the synchronous motor. :frown:
http://sti.discip.ac-caen.fr/sites/sti. ... iphase.pdf

Only the synchronous motor can operate alternator and vice versa, but they are really effective in the function they were designed http://olivier.dehaupas.free.fr/upload/ ... NATEUR.pdf
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Re: Generating Experimentation




by Forhorse » 12/08/17, 09:07

It is quite possible to transform an asynchronous cage motor, three-phase alternator, it is very simple, just connect a capacitor bank in parallel to it.
The value of these should be roughly equivalent to the value it would take to bring the cos-phi to 1 in motor use.
To have the right frequency and approximately the correct voltage, the motor must be driven at its speed of synchronism + slip.
It may be necessary to adjust the value of the capacitors.

No need for a battery or anything to prime the generator so formed, the remnant magnetism and the capacitors do the rest.
On the other hand, the stability of this generator depends on the balance between the reactive energy of the motor and that of the capacitor.
If we connect an inductive load (or capacitive ...) on such a generator, it is necessary that the cos-phi is fully compensated if it is désamorce.

EDIT: I already did it in my younger days, just to experiment, so do not come and tell me it's impossible.
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Re: Generating Experimentation




by chatelot16 » 12/08/17, 10:39

note on asynchronous motor alternator that I saw on certain generator: there is 2 winding as a single-phase motor: one of the winding is the output of 220v ... the other phase winding of 90 ° is connected only on a capacitor ... it makes a voltage more stable than if the capacitor was on the main winding

in the case of a tri motor, one can take the single-phase voltage between 2 phase, and put 2 capacitor on 2 other phase
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Re: Generating Experimentation




by izentrop » 12/08/17, 11:00

Forhorse wrote:It is quite possible to transform an asynchronous cage motor, three-phase alternator, it is very simple, just connect a capacitor bank in parallel to it.
An example is necessary, because the operating principle of the electric generator is the current induced in a conductor moving in a magnetic field, Lenz-Faraday law.

The capacitors across the windings will not create this magnetic field. And even if it did, how do you get the power back from the "squirrel cage"?
chatelot16 wrote: asynchronous motor alternator
??
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Re: Generating Experimentation




by Forhorse » 12/08/17, 22:50

It is necessary to inform you because it is a principle known for a long time. There is easily a literature on the subject so I will not embark on a scientific explanation that would be inaccurate and incomplete anyway.
But in principle, all rotating electrical machines are reversible, more or less easily, with a more or less good performance.
How does an asynchronous cage motor work? Basically the rotor is not magnetized, it is the rotating field that causes induced currents that had even caused a magnetic field around the rotor. These induced currents can only exist if the rotor rotates less quickly than the magnetic field of the stator.

Well, as a generator it's exactly the same thing, capacitors are basically used to provide phase-shifted reactive energy to the stator. This causes a rotating magnetic field which is not in phase with the rotation of the rotor => an electrical conductor moving in a magnetic field .... all that all that ...

The problem is that this generator needs to be supplied with reactive energy (by the capacitors so) and that if we connect a load that consumes too, it will no longer be available for the generator (or not in sufficient quantity) below a certain threshold the phase-shifted field is no longer sufficient, the output voltage drops, the capacitors thus provide even less reactive energy, which further weakens the phase-shifted field, etc. In short, the generator is defused.
So it's going very well for a resistive load (typical case: the owner of an old mill who wants to heat his house with the rotation of his wheel using a sorting motor recovery)
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Re: Generating Experimentation




by izentrop » 13/08/17, 00:20

Yes indeed I had forgotten this mode of operation which is very sharp: electrical-electronic-computer / asynchronous-motor-alternator-en-t6820.html
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