Efficiency

Question: what is the power consumption of a single PCB motor without taking into account the driving electronics ?

Answer: The power efficiency of the stator is low, 5-10%, comparing input power to power on the shaft. Unfortunately, this is tightly connected to the friction which is providing the motor torque, so the efficiency cannot be improved significantly. Material losses at low temperature are generally lower, so some improvement could be gained by working at cryogenic temperatures.

The efficiency of a well tuned driver is around 90% and could probably be improved even further.