12 Volt DC Motor Generator Problem

[Cbronson]

In my experimental project I require a low rpm dc generator to charge a bank of 12 volt storage batteries.
A rotating shaft alternates in direction with a full rotation of 180 degrees, and, the shaft speed is low. It is a high torque power device and with magnetic gearing, the rotational speed can be around 150 rpm.
Alternators for small autos, motorcycles require too high a rpm. In my research the literature suggests the use of higher voltage stepper motors as a generator. A commercial permanent magnet dc generator is also suggested.
Because the shaft alternates in direction I feel this may restrict my options.
I would appreciate any ideas on how I can generate the required 12 volt dc voltage.

 

[waross]

Use a high ratio gearbox to increase the speed to where you can use a readily available generator, alternator or PM motor.
Use a drive belt and a one way clutch to drive the gearbox. Use a second crossed drive belt and one way clutch to also drive the gearbox so that no matter what direction the input shaft is turning, the gearbox and the generator always turn in the same direction.
Use your back to back drives as a first step when velocities are low. That saves you from the waste of accelerating and decelerating inertias at higher speeds. A flywheel may help but if it is to large, something will break.

Bill
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"Why not the best?"
Jimmy Carter

 

[Cbronson]

By use of magnetic gearing I am experimenting with a way to rotate the shaft in one direction and also, magnetic gearing ratios to have a rpm of 200 to 300. It would not be practical to have a higher rpm. The use of magnetic gears would keep the overall frictional forces low as possible. With exception of the magnetic gear attached to the power drive shaft all other magnetic gears would rotate freely on shafts and transfer the power.
The use of a commercial permanent magnet generator designed for low rpm’s with 12 volt dc output or above would probably be the best choice. These are available from several sources but, the one drawback is the cost!
Thanks for your reply.