Page 341 - CITS - Electronic Mechanic - TT - 2024

ELECTRONICS MECHANIC - CITS

Brushless DC Motor Construction
There are several different configurations of BLDC motors, which vary according to their stator windings that
can be single, two, or three phase. The majority of BLDC motors have the three phase design with a permanent
magnet rotor. The stator for each type of BLDC motor has the same number of windings.

BLDC motors can be inrunner or outrunner where an inrunner brushless motor has the permanent magnets inside
the electromagnets while an outrunner has the permanent magnets outside the electromagnets. The working
principle for both designs is the same with different configurations.

Stator
The stator produces the magnetic force that causes the rotor of a brushless DC motor to spin. It is either inside
and surrounded by the rotor or outside enclosing the rotor. The stator is made up of laminated steel stampings
stacked together to form a magnetic core. Coils of wire are wound around the core and are connected to the
controller.
The pieces of steel of the stator can be slotted or slotless with slotless cores being capable of producing high
speed motors because of low inductance, a design that is more expensive since it requires more coil turns.
Rotor
The rotor contains a permanent magnet with two to eight pairs of poles with alternate south and north poles. The
magnetic material for the rotor is carefully chosen in order to produce the required magnetic field density. The
types of magnets for the rotor can be ferrite or neodymium.

The different core configurations are circular with permanent magnets on the periphery or circular with rectangular
magnets.

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CITS : E & H - Electronics Mechanic - Lesson 205 - 222