I will disagree with you, Patrick, about sensored motors, and there is no "Hype" here. For given application there is a given motor.
Brushed motors can deliver 1000% torque at stand still
Sensored Brushless motors 1/3 of that
Sensoreless not even 20-30% of that sensored systems
You know why and there is no BS here.
Extra wires and sensors are weak links as well as brushes, as long as mentioned them.
Timing with sensors can me more advanced and flexible if you write software accordingly and there is no need to set sensors exactly at "0", you can adjust it anytime as wide as you wish. And back check with motors efficiency, you can even run in dual mode and use sensors for back-check, startup, pulling, holding and braking. If you creative you can even generate brushed mode. Just need to set sensors perfectly spaced to motor poles. If you use encoder instead of hall-sensors, or even IC you can be completely independent of motor type/pole count. I am not going too deep in details, but I think you know the rest.
All the rest about sensored systems in only limited by flaws in software.
I actually was saving this sensored idea from suicideneil for desert, but I guess it would be impossible to convince you otherwise... :(
To BrianG:
Quote:
|
The common consensus here seems to shoot for a battery and motor kv setup to get around 30-35k rpm total. This most likely came about because Feigaos tend to heat up at speeds higher than that. However, lower rpm means less EMF pulses at really slow speeds, which increases the chances of cogging.
|
Brian, I wasn't expecting question like that from you. Efficiency curve defines given motor RPM range. Number of Poles, Motor diameter and rotor length defines torque and speed factors. (Rotor weight, air gap, core material, windings, delta/star...) From motor parameters you can plot it quite easy.
For the same Power motor with
More poles -> Lower RPM Higher Torque
Less poles -> Higher RPM Less Torque.
Smaller diameter -> Higher RPM, Lower Torque
Bigger diameter -> Lower RPM, Higher Torque
Longer rotor -> Lower RPM, Higher Torque
Shorter rotor -> Higher RPM, Lower Torque
I do not even know what to comment on "Less" EMF pulses...
I will call it Monday and I am in bad mood and picky, sorry for harshness.