Tuesday, March 9, 2010

Brushless Motor Construction

Brushless DC (BLDC) Motor Fundamentals

BLDC motors are a type of synchronous motor. This
means the magnetic field generated by the stator and
the magnetic field generated by the rotor rotate at the
same frequency. BLDC motors do not experience the
“slip” that is normally seen in induction motors.
BLDC motors come in single-phase, 2-phase and
3-phase configurations. Corresponding to its type, the
stator has the same number of windings. Out of these,
3-phase motors are the most popular and widely used.
This application note focuses on 3-phase motors.

Brushless DC Motor - Basic structures

The construction of modern brushless motors is very similar to the ac motor, known as the permanent magnet synchronous motor. Fig.1 illustrates the structure of a typical three-phase brushless dc motor. The stator windings are similar to those in a polyphase ac motor, and the rotor is composed of one or more permanent magnets. Brushless dc motors are different from ac synchronous motors in that the former incorporates some means to detect the rotor position (or magnetic poles) to produce signals to control the electronic switches as shown in Fig.2. The most common position/pole sensor is the Hall element, but some motors use optical sensors.

Brushless Motor Construction Video
Machining A Brushless Motor with a lathe and drill press. Just a quick slide show of some motor contsruction tips before I added a small milling machine to my hobby shop. John  

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