September 2010|Online electrical engineering & Electrical Interview Questions

Tuesday, September 14, 2010


First of all what are Brushless DC motors?   In normal DC motors  carbon brushes are used for commutation.Whereas in Brushless DC motors power electronic devices are used for commutation.This type of commutation is called as Electronic commutation.

Based on construction of the motor ,BLDC motors are classified as In-Rrunner and Out-Runner.In In-Runner type, the stator encloses the rotor and in Out-Runner type,the rotor encloses the stator.

Where do you use the BLDC motors?
Almost everyone will be using computers.You must have seen the fans used for cooling your CPU.These fans are nothing but BLDC motors.They are all of Out-Runner type.Just take a PC fan which is not working,and break it and see.You will see stator windings with 4 poles or 2 poles around which a permanent magnet is placed which acts as rotor.The fan blades are attached to this rotor magnet.