Coreless motors use a lot less power and last longer...
This is due to the motor design; coreless motors use wipers instead of the carbon brushes used in standard motors. Also Coreless motors do not have an iron armature. Instead it is usually a light weight plastic with the magnetic wire wrapped within it. This allows a quicker response due to the low mass of the core and reduces the interaction of the magnetic fields with core.
The brushes for a coreless motor are very small; they are wipers. This reduces the overall loss caused by a carbon brush. Wipers also increases the life span of the motor due to better wear characteristics (no sparking and less pressure on the commutator, with the no sparking of the wiper, electrical noise is minimized while the lack of arcing reduces "pitting" and "debris" from the caused by standard carbon brushes). Additionally, wipers have a smaller "contact"
patch on the commutator; there is less friction compared to a brushed set-up.
1. Cost, coreless motors are more expensive; this is due to the wiper tolerances and generally, higher quality magnets are used.
2. Wipers require a little more care with the Frequency used to control the speed. A higher frequency controller would be necessary to prevent arcing on the commutator; this would cause excess wear and power consumption. Obviously with the requirement of a higher frequency, the transistor switching will need to be much higher therefore more expensive components would be required. (This is transparent to us because this is controlled internally by the servo. It is a nice to know for the possibility of using these types of motors in a high current environment, i.e., airplane/heli drive motors.)
As for a brushless; they are actually a DC Electronically Switched Commutator motor. There are no brushes to wear. Instead the speed control senses the position of the rotor using the coils in the stator to decide on which coil to energize. This is done sequentially to turn the motor. This is a very efficient design and has a relatively long life span.
Brushless motors are more expensive due the magnets that are used. Brushless motors can handle very high speeds because of this.
The do require a special controller to handle the switching. Some of the older designs have hall affect switches on the shaft to tell the controller the position rotor. The newer stuff do not use these sensors hence "sensor less Brushless Controller".
Also Brushless motors could handle more abuse and higher operating temps. Coreless are a little more sensitive to this kind of abuse.
I hope this helps...
Is that a 6s 5000 in your pocket,
or are you just happy to see me?