# Getting a higher voltage from an induction motor

1. Dec 1, 2008

### caesius

Experimenting with building a wind turbine and I'm trying to find a suitable motor.

I got this induction motor out of a washing machine and have hooked it up through a bridge rectifier and a smoothing capacitor.

Spinning the motor shaft by hand (a crude way of modeling how fast the wind will rotate the blades) I am able to achieve around 9-11V no problem.

I'm told I need at least 14V to charge 12V deep cycle batteries, my question is: is there anything I can do to achieve a higher voltage from this setup? I'm thinking modifying the motor to achieve this. Or am I going to have to find a new motor?

Here's a pic of the motor if that helps

http://img211.imageshack.us/img211/7842/dscf0004pz2.th.jpg [Broken]

Last edited by a moderator: May 3, 2017
2. Dec 1, 2008

### triden

My motor knowledge is limited, but I might be able to throw some ideas your way.

An increase of speed will increase the voltage output of the motor. It will also increase the frequency of the output waveform, but that doesn't matter too much since you are rectifying it. The only thing is, there is a threshold where increasing the speed won't produce more voltage. The next step would be to increase the number of windings on each pole of the motor. When the magnets pass by the field windings, a voltage is induced proportional to the number of windings in the pole.

Short of giving your motor more windings, I think the easier way would be to find a 220v or even a 600v AC motor. This should give a higher voltage for a similar RPM.

3. Dec 2, 2008

### uart

What type of rotor does that machine have caesius, is it wound rotor or squirrel cage?

Induction motors do not normally operate as alternators unless you externally provide the excitation. Can you please explain exactly how you have it connected and what sort of excitation you're providing.

4. Dec 4, 2008

### m.s.j

It seems you have a small DC generator. Generally the control voltage of dc generators may be achieved by controlling the field flux or the speed of the prime mover. For a permanent magnet DC generator the field flux is constant and hence the terminal voltage may be controlled by manipulating the speed of the prime mover.

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5. Dec 4, 2008

### Staff: Mentor

Isn't that motor a good 10x the size it needs to be? Perhaps a car alternator or small DC motor would be better?

6. Dec 4, 2008

### mheslep

If this is an induction motor as posted, it is by definition an AC motor. Induction machines with squirrel cage rotors must run at near rated RPM (either as motor or generator) generate any power. If you hook up this motor appropriately it should generate rated voltage (120AC). So to be useful for wind you will need a gearing system, meaning losses to friction, which I don't think will work well with a wind turbine. You really want a permanent magnet motor which is rare in household motors, as far as I know.

Google is your friend on this one: try "washing machine motors as generators"