Electrical Question

[teddy52food]

I have a question to the electrical experts.( Bob M. and John T.) Or anyone else. How much wattage would it take to overcome the friction on a set of off the shelf bearings that support a 2 inch shaft going through a rotor that weighs over 1600 pounds?

 

[Jaden]

Question for you; How fast do you want to turn it and how fast to get up speed? (The inertia of the rotor counts)
John

 

[teddy52food]

Let's just say 100 RPM.

 

[teddy52food]

In a minute or less.

 

[Anonymous-0]

There is a little more information needed before the wattage can be calculated. What is the size of the rotor(diameter, thickness)? Is the motor directly driving the rotor or is it connected via a chain or belt? If it is not directly connected, what are the sizes of the sprockets or pulleys?

 

[buickanddeere]

Bearing friction alone or windage? Rpms, dia, turbine blade rotor, generator rotor, squirrel cage motor rotor?

 

[teddy52food]

Rotor is in a hand built motor about 9 inches in diameter and 9 feet long.

 

[MarkB_MI]

Really your question is more mechanical than electrical. You really need to determine what torque is required to overcome the static friction of your bearings. Once you do that, it becomes a matter of sizing a motor with sufficient torque at zero rpm. Starting torque and operating horsepower (or "wattage", as you say) are pretty much independent of each other; starting torque depends a great deal on the particular type of motor.

Is this a real problem or a theoretical one? If it's theoretical, you can pick bearings that have almost zero static friction, in which case the starting torque would be small. At the other end of the scale, babitt bearing have very high static friction.

If you actually have this device built, you can put a torque wrench on the shaft and measure how much torque it takes to overtake the static friction in the bearings.

 

[buickanddeere]

40W-65W per bearing depending....... Too much or too heavy grease will raise the number.
Windage,hysteresis, iron eddy current losses, I2R losses are going to make bearing losses the least of your worries.

 

[cadet trooper]

That's a pretty good size rotor.

 

[teddy52food]

Would you believe it is running on less than 5 ,I repeat, 5 watts! Please open your E- Mail. Thank you. Or E-Mail me anytime.

 

[MarkB_MI]

I would not believe it is running on 5 watts, and I'd have to question how you're measuring the power. That's only about 40 milliamps at 120 vac, even with unity power factor.

 

[teddy52food]

Go to the Joseph Newman website and watch the Speed is power vidieo

 

[teddy52food]

It is a permanent magnet.

 

[MarkB_MI]

I've been suckered again. Here I thought this was a serious question. No, it's yet another perpetual motion machine.

Sorry, but the first three laws of thermodynamics still hold true.

 

[teddy52food]

No, you have not been suckered. No, it is not perpetual motion. He is not breaking those laws. It gets its energy (works) E=mcsquared. From a permanent magnet and a coil of copper wire.