What happens when OU is reach?

[gyulasun]

I don't think a OU motor will spin out of control.
It still has to obey the laws of torque and speed.

Meaning:
A motor have Maximum Torque when being stalled to Zero RPM.
A motor have Zero Torque at maximum Free Spinning RPM, but the top speed is limited by friction and airpressure.
A motor delivers Half the Stall Torque when being loaded down to Half the Free Spinning RPM.
At this level a motor can deliver Great Powers at Good RPM. This is the most efficient working point.

Hi Honk,

Yes you are basically correct but I simply would be worried to run such motor (that runs by its own power)  without a deliberately built-in control means like a voltage stabilizer.  Without such stabilizer the output power
would always change whenever the amount of the useful load changes.  Agree with this?

(I do not mean to use a voltage stabilizer for the total output power,  I mean only to run the motor via a stabilizer because I assume the motor gives out higher torque when its supply voltage increases and this working mode creates an uncertain, very load dependent operation if the supply voltage of the motor is uncontrolled.)

rgds,  Gyula

[Honk]

Hi Honk,

Yes you are basically correct but I simply would be worried to run such motor (that runs by its own power)  without a deliberately built-in control means like a voltage stabilizer.  Without such stabilizer the output power
would always change whenever the amount of the useful load changes.  Agree with this?

Oh yes, you are right. But the stall torque from magnets within such a design will not increase or remain the same while running.
It will decrease by speed as usual. This is the limiting factor.
If the stall torque instead remained unchanged by speed then we would have a potential self runner out of control.
But as we all know (at least some of us) torque decreases linearly by speed. And there is no way around this fact.

(I do not mean to use a voltage stabilizer for the total output power,  I mean only to run the motor via a stabilizer because I assume the motor gives out higher torque when its supply voltage increases and this working mode creates an uncertain, very load dependent operation if the supply voltage of the motor is uncontrolled.)

If the motor can run totaly on it's own there is no need for an input. Stall torque will be the limiting factor.
But if the rotation is controlled by electromagnets then the generator voltage will need adaptation to fit the input needs of the motor.
In this case the stall torque and the power of the electromagnet and control unit will limit the motor.

[wattsup]

@Honk

Glad to see you are around.

If the motor is AC, there will be phasing issues from output to re-input. I have tried putting raw AC output to re-input and it is not a pretty site or sound. lol

I am wondering, if using DC, what if you put a nice fat resistor on the input so there could not be any more power then a specified level. This would mean the motor side would not consume more power, so the output side would not need to make more power and create more drag.

[Honk]

I'm still here....and going strong.

Unless you want heating as result the resistor is of no good use.
It's better to extract the excess power from a generator.

[Low-Q]

Regarding useful torque, I believe that it is not a linear function of speed, but a logaritmic. The loss in a motor at 5000 rpm is four times greater than 2500rpm. It means you must put in 4 times the energy to double the rpm.
Stall torque has almost no loss, as the rotor stands still, but the torque will be more and more "busy" with the increasingly losses in the system as it speeds up. At the end there is no torque left to do proper work other than keeping the motor running at a certain maximum rpm. So when the motor is loaded you convert the loss into work by decreasing rpm.

So I believe that the torque is constant regardless of speed/rpm (speed of torque is the same as speed of light), but the useful torque which we can convert in to energy are changing in a logarithmic scale.

br.

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