# Electrical Engineering/Dynamic brake design

Question
Say I have a wheel rotating at 1 rpm with 100lbs of force. If I were to let this wheel rotate freely, it would accelerate to a very high rpm, but I don't want it to. I always want it held at 1 rpm. I'm not an expert, but I feel that the best way to do this would be to use a dynamic braking system. I do want to use some of the electricity generated, but not all of it. In my mind, I would think I need to gear it to where I have a shaft rotating at a much higher rpm. Then match the amps of the traction motor to the torque of the shaft, and match the voltage to the desired rpm of the shaft. Now that motor connected to the shaft is creating electricity. I then take the electricity I want out, and then I have another motor that I run to waste the rest of the electricity that the shaft motor is generating. Would this system then hold the wheel at the rpm I want, since it takes that amount of energy to create electricity, and then I'm using it all? The goal being to provide an equal resistance to the energy generated, thereby preventing the wheel from accelerating.

There are many ways to keep the wheel at a constant rpm.  One way is to load it down with friction or generator breaking as you have described above.  You can draw off generated electricity to another loading area or you could friction load the generation into a resistive heat producing load.

Another method is using servo systems which are controlled by servo circuits that can keep the servo system constant.

https://www.servocity.com/html/1_rpm_gear_motor.html

http://www.pololu.com/category/143/continuous-rotation-servos

http://www05.abb.com/global/scot/scot239.nsf/veritydisplay/8492cb383e941d5785257

And so on.  If you want more details there are many tutorials on this subject online.

http://www.electronics-tutorials.ws/systems/closed-loop-system.html

Above is an example.

Best wishes.

Electrical Engineering

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#### cleggsan

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