Motors are not a new concept, I suspect that if you stopped arguing you might just google an answer for yourself? People who don’t want to disagree with each other at a fundamental level have likely found the solution to this some time in the last 100 years.
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The answer is water bottles.
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i did just that in the original discussion which was deleted from the noob thread for being too not noob
here’s a repost:
^the green line, left chart shows that when powered, torque ripple is less in BLDC mode than FOC in a hummie motor which doesn’t use distributed windings
if the motor used distributed windings, ie more than one phase per shared tooth, foc would result in less torque ripple when powered
that covers the powered side of the debate.
the unpowered side is covered by a simple conservation of momentum argument which conflicts with hummie’s statement that cogging causes “loss of momentum” without induced eddy currents
I was programming my Unity via bluetooth. Everything would work until I clicked “write updated config” it would hang. I had a terrible time getting it to calibrate and recognize my remote. Whenever I got it to work…I had terrible cogging and weird acceleration. I finally decided to do a USB/PC program and all of my problems were gone…virtually no cogging, excellent acceleration even the battery usage improved. How can a bad config cause cogging?
cogging is when the motor doesn’t turn smoothly unpowered because of alignments between the magnets and stator teeth in the motor
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To be clear it’s that shuddering you get when to start from a stand still…correct? I had to kick off or flick my hips to get it going
Okay clearly hummieee and sharts has some unresolved issues unrelated to cogging
But TRYING to stay on topic here, lets break this down.
Using FUNDAMENTAL LAWS OF PHYSICS:
IF cogging causes loss of momentum. That means energy is lost.
Question is: HOW is the energy lost.
Byproduct: Heat. Energy cannot be lost any other way other than heat.
How is heat created? Resistance.
What resistance? Friction from bearings + electrical
Electrical resistance? Eddy current.
There is no other argument here. Claiming that cogging causes loss of momentum but not due to electrical resistance, where the f did the energy go?
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no that’s actually caused by the vesc not knowing the rotor position in sensorless mode because the non-spinning rotor isn’t producing enough back emf voltage to determine the rotor position with sufficient accuracy
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But it feels like shuddering…correct?
exactly… and if the loss of momentum is caused by eddy currents, then it isn’t caused by cogging. so eliminating cogging won’t eliminate the loss of momentum. eliminating cogging won’t improve the efficiency.
cogging is only when you turn the motor in your hand unpowered and you feel little bumps as it goes around.
Going REALLY in detail, loss of energy due to cogging NOT from electrical resistance: deflection of motor can as the magnets are cogging. Accounts for probably 0.0001% of energy lost due to cogging.
itt depends on the initial position of the rotor. if i place the rotor at the potential peak and let go… it spins spontaneously! that almost seems like free energy even though it itsn’t. where’d the energy come from? it was stored when i used energy to turn the rotor towards the location of the potential peak. then i got the energy back when i let go, minus the energy it took to make some eddy currents and bearing heat.
Oh, I meant physical deflection of the motor can, i.e. the can warping by thousandths of a mm due to the magnets pulling at different strengths. The flex of the metal in the can will create a minuscule amount of loss as heat. Need electron microscope to measure deflection %.
Don’t need to prove the fundamental laws of physics. Law of conservation states that momentum can only be lost as mass and heat. Unless the motor is actively getting heavier, that means all loss of momentum is lost as heat. Heat is generated by only mechanical friction or electrical resistance. Which means when you claim a loss of momentum in a motor, it is due to either bearing friction, or electrical resistance aka eddy current. Claiming anything else is claiming that motor is defying laws of physics.
/endthread
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How bout argue cogging is hysteresis. At least they are produced linearly w erpm and not exponentially. But both of them produce their loss at speed. Spin motor on bldc tool at no load top speed and there u have all the iron losses. Small then and knowing the rate they’re produced it doesn’t make sense that they would decrease at lower and lower speed…and then somehow be the dominant loss at slowest speed.
Also as I said u can have a motor with no cogging at the same erpm if it has no slots. If cogging were eddies where did they all go in a slotless motor ? Disappear when Theres MORE conductive material in the magnet path makes no sense.
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you still have hysteresis even if the motor doesn’t cog. eliminating cogging doesn’t eliminate hysteresis.
Yes. The question is what is cogging. All pm motors have hysteresis and eddies, and in our case with 12n14p motors spun slowly it’s a very small amount.
@Brenternet some answers aren’t out there…such as what exactly is cogging torque.
Cogging is not what causes eddy current, eddy current is only a result of the motor spinning, regardless of whether cogging happens. Cogging by itself should theoretically have no major loss of energy in itself.
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and if you eliminate cogging by filling the gaps between the teeth with iron, you get more eddy currents and hysteresis, not less.