Inverting Power, (big or small) fans

[KeithShap]

Is there any way to invert a fans power, from input to output? I was looking into creating an electromagnetic generator, and was dabbling with the idea of a more compact way would be to place the electromagnetic motor directly onto the motor system of a fan, but with no idea as to how to reverse the power flow, I find myself at a dead end at the moment. IF this is possible, I was wondering if any would be able to tell me how it may be done? Thank you in advance for your help.

 

[LiteYear]

Yes. A motor and a generator are effectively the same thing. Power the wires turns the fan. Turning the fan powers the wires. Is there something more specific you're stuck on?

 

[ScottyUK]

A wind turbine, or similar? A standard 3-phase motor connected to a regenerative VFD could, in principle, work in this manner. You'll need some control processing externally from the VFD too.

 

[ScottyUK]

Clicked too soon!

There are other options too, such as semi-custom generators or a DC generator with an inverter to connect to the utility. A Google of wind turbine generator should provide plenty coverage of the available options.

 

[jraef]

It is possible, it is NOT something an amateur should dabble with unless supervised by someone with specific experience in such things. There are SERIOUS safety concerns involved once you begin generating power and from the general tone of your post, you do not appear to be qualified to take this on at this point. A consequence of doing it wrong could be as dire as killing or maiming a utility line worker.

Commeriall off the shelf Wind turbine power generators typically come with a very specific isolation system to make this more palatable to power utilities, but making your own from scratch will not have that benefit.

"Will work for (the memory of) salami"

 

[iceworm]

Keith -
Perhaps you are thinking of an induction alternator (sometimes called "induction generator"). A loaded induction motor turns 2% - 5% slower than synchronous speed (slip frequency). So if one connects the induction motor to a driver and over speeds the motor 2% - 5% over synchronous speed, the motor can push power back on to the line.

The only ones I've seen are 3 phase and must be connected to a grid. The grid provides the magnetizing current for the motor - won't generate with out that.

I've heard anecdotal accounts that one can do this with a 1ph motor - but I have not seen any working models nor any credible papers.

I've heard similar accounts one can provide the magnetizing current (to a 3 phase motor) using a cap bank - and not connecting to a frequency stable grid. Again no papers available. Additionally I don't see how this could work. With no stable grid, what would be the slip frequency?

One might consider an inverter/battery bank/charger. Spin the motor up to synchronous speed, connect inverter to the motor leads, start the inverter on the batteries to provide the stable frequency, over speed the motor to generate, connect the gen output to the inverter battery charger. I've not seen any papers on this, nor heard of any working models - but the physics sounds good.

Yes, one needs to be concerned about safety. And it is a really good idea to not co-generate with out a utility agreement. Having said that, maybe you will go down in history as the flux capacitor inventor - Keep thinking.

iceworm
Harmless flakes working together can unleash an avalanche of destruction.

 

[electricpete]

I've heard similar accounts one can provide the magnetizing current (to a 3 phase motor) using a cap bank - and not connecting to a frequency stable grid. Again no papers available. Additionally I don't see how this could work. With no stable grid, what would be the slip frequency?

Self Excited Induction Generator is well detailed in the textbook "VARIABLE SPEED GENERATORS" by Boldea. Probably many other places,.

For a typical induction machine connected to sync grid, we have no problem imagining that the line frequency is fixed/known and the machine speed adjusts to produce a slip which will give desired torque.

For SEIG, just consider that the machine speed is known... then the line frequency is what adjusts to produce a slip which will give desired torque. It is produced by the machine itself.

I agree about the op, seems a little wandering. What is the engineering project being underaken?


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(2B)+(2B)' ?

 

[iceworm]

I've read a few of Boldea's papers. He is a very prolific writer. His insight, as is your's, far exceeds mine. Thought I could find his papers last night - couldn't.

So, As I Recall, for self-excited, holding voltage and frequence is very difficult. Driving any kind of a load requiring vars is nearly impossible. Unless one wishes to deal with leading static var compensation and some serious frequency feedback speed control it is uncontrollable.

Of the two examples I recall, both drove into rectifiers, the unstable voltage and frequency was unuseable for AC loads.

However, regardless of this, you are correct. There are creditable papers showing Self-Excited as capable of generating power.

ice

 

[KeithShap]

Thank you all for your replies. You've def. given me enough to read on for a little while. I am very aware of the hazards when it comes to ANYTHING electrical. If I were to try anything, it would be on a small scale, and use a generator so not to cause any harm to the existing power grid. Non of this is going to even see prototype faze until I can get some sort of cash flow. So no worries on possible death, for awhile at least.

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