Interpreting FEMM results

[tao]

Yes, the positive and negative torque values equate to the clockwise/counter-clockwise twists.

No, Positive torque equals anticlockwise movement about 0,0.  Negative torque equals clockwise movement about 0,0

Any third opinion?

I was just saying that the positive and negative values of torque tell you which way the pieces are rotating, either clockwise or counter-clockwise depending on the value.

[tao]

You must move your simulation on the grid in FEMM such that it is symmetrical about the absolute point 0,0. I do this as I am building each of my FEMM sims, I also build them about point 0,0.

Thanks, I guessed that this was true and have started to move the center of rotation for my models to the absolute 0,0 point on the surface.

But this brings up another question:

What does it mean to select a block and then ask for torque? Are we in effect asking "what torque does THIS block exert on 0,0"? Does it make sense to select all the elements of the model, including the air, and then ask for torque? (as long as they all are physically connected somehow)

Depends, for instance, I circular magnet (designed as the rotor) centered over 0,0 and selected it to determine how much torque it was feeling. Or, I could pick all the elements around this magnet (which are in effect the stator) and check the torque value and it was exactly opposite that of the magnet at 0,0 (which of course would be the result).

You have to pick the pieces based on knowing what is supposed to rotate or not. You don't need to select the air, because FEMM is taking all the pieces that you don't select into account when you calculate torque for any given piece/pieces.

[ken_nyus]

Depends, for instance, I circular magnet (designed as the rotor) centered over 0,0 and selected it to determine how much torque it was feeling. Or, I could pick all the elements around this magnet (which are in effect the stator) and check the torque value and it was exactly opposite that of the magnet at 0,0 (which of course would be the result).

You have to pick the pieces based on knowing what is supposed to rotate or not. You don't need to select the air, because FEMM is taking all the pieces that you don't select into account when you calculate torque for any given piece/pieces.

Thanks tao, that helps. I like the idea of checking results against each other to see if things make sense.

[ken_nyus]

I was just saying that the positive and negative values of torque tell you which way the pieces are rotating, either clockwise or counter-clockwise depending on the value.

Thanks tao, but acp disagrees and says the opposite, so I am still not sure which it is. I tend to think that a positive value would be clockwise, and a negative value counter-clockwise but that is just my cultural bias in thinking.

I tried constructing examples where I felt I could predict the twist, and compared my expectations with the FEMM result, but then I realized I wasn't sure about 0,0 and other things, so the results confused me.

[tao]

I was just saying that the positive and negative values of torque tell you which way the pieces are rotating, either clockwise or counter-clockwise depending on the value.

Thanks tao, but acp disagrees and says the opposite, so I am still not sure which it is. I tend to think that a positive value would be clockwise, and a negative value counter-clockwise but that is just my cultural bias in thinking.

I tried constructing examples where I felt I could predict the twist, and compared my expectations with the FEMM result, but then I realized I wasn't sure about 0,0 and other things, so the results confused me.

I never said that positive = clockwise, I was just answering your original question, and acp incorrectly corrected me, even though I never made that statement.

To be clear, if it's needed:

positive torque value = counter-clockwise rotation
negative torque value = clockwise rotation