From what I have garnered regarding coreless motors, wind them as you would a cored motor. The only difference is the absence of ferrite material in the armature. Because of the absence of the reluctance we see in an iron armature the coreless motor is more efficient but invites much higher current spikes when driven with a PWM speed control.
They are much like the term "slotless motor" used in brushless servomotors where the stator has no iron. Coreless motors are DC brush type were you remove all the iron from the armature. Coreless motors are sometimes called basket-wound motors.
Coreless motors armatures have a much stronger field, therefore much more efficient but have poor cooling capabilities. Another disadvantage is that coreless motors have low inductance, therefore can have heating problems if you don't have a high switching frequency....
Just do a search on the web for coreless motors and I am sure you will find many sites with information. Companies like Maxon, MicroMo, Pitman, Portescap...and others have coreless motors, but I'm sure they are not sharing winding information your looking for.
Cameron Anderson - Sales & Applications Engineer
Aerotech, Inc. -
On the topic of small (.5W, 12mm dia, 6k rmp) coreless motors, does anyone know if a break-in period extends the life or improves the performance of the commutators? We have problems with failures in the field with a motor that look like burn marks on the commutators, running low duty cycle within the current (1.2 Vapp on 8.8 ohm winding) and temperature specifications of the manufacturer. Since these structures are so small, I'm wondering if break-in at low speed might remove irregularities on the contacts, reducing noise and possible arcing.
Suggestion: This may need some experimentation results from the motor manufacturer tech support, e.g. application notes, since normally the break-in period extends life; however, the starts and stops may be reducing life expectancy noticeably.
SHunter - I know the commutators are very small on this type of motor (I think it is to keep the peripheral speed of the commutator down, minimizing the forces), but you shouldn't need to bed in the brushes.
One of the characteristics of this type of motor is that they are low inertia, i.e. they suit applications with continuous stop/starts and speed changes generally. They shouldn't be causing you problems as you describe. If the manufacturer can't help, I would be thinking about an alternative supplier.
