Need Help with converting motor to generator.

[goodpickles]

I have a 3 phase motor, I have heard that it is possible to make a generator out of one. Can anyone give me more information?

 

[bogdanfirst]

well, here is how it works...
if the motor has magnets inside it, then just by rotating it you can get current..
if not.....
you need to modify it. you need an external power spource to power the stator and get power from the rotor.

 

[goodpickles]

It does not have magnets. I could probably use a transformer and battery for the power source? How would I get the power to the stator?

 

[spuffock]

The usual type of 3 phase motor is known as an induction motor. The rotor windings cosist of heavy copper bars arranged as short circuit turns,and there is no provision for connecting anything else to them. The rotor current is induced by the rotating magnetic field from the stator.
You can easily tell this type of motor by the fact that the rotor appears to be a solid lump of iron, with no brushes or sliprings. If this is the case, then it is not worth the trouble to proceed further. If anyone knows better, then I look forward to being corrected.

 

[Klaus]

I second that - it being neigh impossible to make a generator out of a squirrel cage motor. If the rotor had 3 slip rings, as some soft start motors do, you might make a generator by feeding current into the rotor.
Smaller 3 phase motors are almost exclusively of the squirrel cage type.
Klaus

 

[morg2625]

here's a link to do that.

[Induction Generator [/URL]

 

[electronic spark]

The last post is ok for portable use - I didn't know that you could run induction motors like that with capacitors without grid (mains) power. If you have grid power and who doesn't?, then you can easily have grid interconnected AC induction motor and feed your power into the house wiring and if you produce more than you use turn your meter backward (of coarse if your meter is allowed to turn backward, here in Ontario, Canada they will turn backwards). If your meter is not allowed to turn backwards, you can still slow down your meter by the amount you produce or stop it.

Here is how it works. You plug in the motor into 120V or 220V, whatever your electric grid is in your country or 3 phase, if you have it. When your motor is running at whatever RPM, then you turn it by a fas motor or windmill or bicycle pedal power and you turn it faster then it is turning when it runs, you automatically make it a grid-connected generator that produces the same exact power as your grid (house) electricity

No inverters, batteries. The control that you have to have is to have spin the motor faster than it normally runs, then connect it to your house power.

Keep in mind that it will only produce as much power as the motor is rated at, i.e. almost 750W for 1 HP motor, but you have to have little more than 1 HP driving it or big enough propeller to be able to generate at least 750W (see propeller sizing elsewhere in this forum).

So the only this makes sense if you have a source to drive it other than your electricity in the house - still all the same laws of physics apply - you can't create more than you put in (because of inefficiency of both source motor or windmill and generator). Of coarse you cannot use another motor to drive the generator and expect to see the meter slow down or turn backwards.

So hey if you have this rotating source to turn a motor faster then it turns hooked up you have a grid interconnected generator.

 

[Hero999]

[Induction Generator [/url]

[SIZE=+1]Notice the capacitor set-up. Here I am trying a suggestion found in an old article, which stated that it is possible to use DC electrolytics connected in series, + to +, and - to - in an AC circuit. I have 4 capacitors rated at 850 uf, 400 VDC in series, for a total of 225 uf @ 1600vdc . The connection is like this: [/SIZE]
[SIZE=+1]AC Lead to motor 0----+||------+||------||+------||+----0 AC Lead to motor[/SIZE]

[SIZE=+1]Shouldn't you add diodes across the capacitors to protect them from reverse voltages?
[/SIZE]

 

[electronic spark]

I have not used them in motors, but in tester circuit and in old tube radio without diodes.
You can use two instead of all four, connecting - with minus or + with + and get 400uF able to handle 800vac. Just keep in mind they need to be rated the same and have the same capacity (not one old, one new), you can test them with a simple DC voltage source and resistor in series placing voltmeter across the capacitor and timing the charge/discharge cycle.

 

[keith]

A grid connection is not necessary. The capacitors will establish a magnetic resonance with the 'inductors' sufficient to provide a starting magnetization flux.

 

[electronic spark]

OK, but if you hook up to grid and spin it fast enough (5% faster than its running speed) you will make your electrical meter slow down or turn backward ;-)

 

[Thearmysredneck]

Here's one that might interest y'all **broken link removed**
or you could just machine down the rotor a little and install some magnets and do it that way, mabe use some full wave bridge rectifiers. Mabe a 3p2w6p rectifier would do. Id be sure to run the math to see how much magnetic flux the stator coils were puttng out and properly select the magnets baised on that as to not roast your stator winding out and get full potiential out of it