author=bistander link=topic=4603.msg111185#msg111185 date=1711830718
I agree that your graphs represent a function proportional to the torque magnitude. And may be sufficient for your purpose. But they are not true torque graphs. Using only the information from the graph, one does not know the torque value in newton meters.
Once again, we were not measuring newton meters, we were measuring the torque being applied to the outer rim of the rotor.
Torque applied to the outer rim of the rotor, is not newton meters of torque at the center of axis.
Why you find this hard to understand, i can't say.
Torque and force are not the same
.
A force applied to a rotating body, in the direction of rotation is a torque.
In physics, can a force be applied to a rotating body such that it does not affect the motion?
Obviously, but irrelevant to the topic of conversation.
So not all forces applied to rotating bodies make torque.
Of course.
Torque is often called rotational force.
There you go.
And so the opposite is true, where rotational force applied to a rotating disk is called a torque.
Torque and force are different things
And i thought you almost had it there.
Yes, torque and force in most cases are two different things, except in regards to the situation being discussed here.
No, It's the Lorentz Force Law which governs the interaction of the magnetic field in the electric motor, not his torque law.
I fail to see your point here, as the Lorentz force results in exactly what I said-a torque imparted on the outer rim of the rotor in a motor.
Question- does the Lorentz force in an electric motor result in a torque being applied to the outer rim of the rotor
Answer- Yes, the Lorentz force in an electric motor does indeed result in a torque being applied to the outer rim of the rotor.
So I am not sure as to why you are arguing with your own admissions here ?
Your graphs were of the force read from the spring scale which is force
Yes, the scales (pressure pad scales, not spring scales) were measuring the value of force being applied to the scales from the resultant torque being imparted onto the rotor, which was created by the Lorentz forces within the magnetic fields.
The force is applied at a distance from the center of rotation and thereby causes a torque on the rotor shaft.
No, not in the case of the motors being graphed, as the shaft is fixed, and does not rotate.
Stall torque, as all* torque in the electric motor, results from Lorentz forces.
Ah, so you agree that the electromagnetic fields create Lorentz forces, and Lorentz forces cause a torque to be applied to the rotor of the electric motor.
And if we wanted to know the value of this applied torque at the outer rim of the rotor, where this torque was being applied, and not the resultant torque over distance at the center of axis of the rotor, we would do this how ?
You noticed. That's what makes a force plot, not a torque curve. Thank you very much.
Of course, you simply multiply the measured force (N) by the radius (m) to get the torque (N-m).
No and no.
The force measured by the scales is the value of the torque at each measured point.
There is no (N-m), as there is no meters, due to the measurements being taken at the point of the applied torque, and not the center of axis.
You tell us these are static measurements. Therefore at each measurement, the power output is zero. You have 12watts input. Efficiency is power out / power in, 0 / 12 = 0. That's valuable to you? I'll be interested to see how.
Ok, it seems you are still unaware as to what we were doing in the tests and the resultant graphs, so i will try again
We were measuring the difference in applied torque values during the on time of the electromagnet, between the two motors.
We were not measuring P/in to P/out. We were measuring the value of torque being applied to the rotor in that small portion of a full rotation of the rotor, where that small portion is the energy injection to the rotor per revolution.
The power supplied to the electromagnet was kept at the same value throughout each test.
This allowed us to see which motor resulted in a higher torque being applied to the rotor for that same period--which one used the electromagnets energy more efficiently.
Can i make it any clearer than that ?
I mean all information is valuable I suppose, but efficiency isn't obvious from your force graphs.
When in fact, the torque graphs show exactly that. They clearly show which motor uses the fixed value electromagnet field more efficiently.
But your spring scale measures force, not torque. And you plot those force values. Yes, it represents torque. But force isn't torque
.
The scales measure the value of the applied torque.
The necessary moment arm is missing.
Exactly, as there is no moment arm--there is a rotor.
So no ft/lb, no Nm, just the value of the applied torque at the point where that torque is being applied to the rotor-at the PM that is fixed to the rotor.
So no, you can't convince me that force and torque are the same. Stop trying.
Never did try.
What i said was-when a force is applied to a mass that moves in a linear motion, it is call a force.
When a force is applied to a rotating mass, in the direction of rotation, it is called a torque--and that is fact.
Why don't we just ask chatGPT the direct question at hand here
Q- User
In an electric motor, if we wanted to know the value of the torque being applied by the lorentz force to the outer rim of the rotor, and not the resultant torque at the output shaft, could we use scales attached to the outer rim of the rotor to measure the value of this torque ?
A-
Yes, in principle, you could use scales attached to the outer rim of the rotor to measure the torque being applied by the Lorentz force. However, there are some practical considerations and challenges you would need to address:
Sensitivity of the scales: The scales attached to the outer rim would need to be highly sensitive to detect the torque being applied. They would need to be capable of measuring very small forces accurately.
And there you have it.
A direct question, and a direct answer.
I think we are done here.
You are of course free to see and do things as you see fit.
I will continue to do them the correct way, and use well know terms and measurement when testing is carried out.
Brad
Never let your schooling get in the way of your education.
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