Brushless motor

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A brushless motor , also known as a brushless motor , is an electric motor without carbon brushes (sliding contacts). In brushless motors, there is no electrical contact between the moving rotor and the stationary stator .

Brushes are used for the electrical connection between rotor and stator via slip rings or commutator and are subject to wear due to mechanical abrasion and the brush fire . With the brushless electric motor there is no need for slip rings or commutators and brushes. Such a motor has a longer service life .

Distinction

A distinction is made between the number of phases of the applied alternating current

Engines. While one and two-phase motors are mainly used in actuating and positioning technology, three-phase motors are used in drive technology. In all cases these are AC motors. Their rotating field is generated electronically, except for non-controllable drives with three-phase asynchronous machines. The term “brushless DC motor” is imprecise, because it is operated with three-phase alternating current that is generated electronically from a direct voltage.

The second phase required to achieve a rotating field is achieved in single-phase motors, for example, by short-circuit windings, cutouts or auxiliary windings.

If armatures made of soft iron or aluminum (typically: soft iron with a cast-in, slightly coiled aluminum cage) are used, they are referred to as asynchronous motors .
If anchors (often: ferrite mass) are permanently magnetized, synchronous motors are created , i.e. motors whose rotation is permanently connected to the rotating field.

Depending on the type of arrangement of armature and coils, a distinction is made between internal and external rotors . In the case of the internal rotor, the (passive) armature runs inside the coil packs, while in the external rotor it runs outside. Electronically commutated external rotors (BLDC motors) are particularly popular in model aircraft sports because of their better cooling and low power to weight ratio .

Types

Brushless machines include some types of three- phase machines such as three-phase asynchronous machines with squirrel -cage rotors . The rotary movement is caused by the rotating field generated in the stationary stator .

Brushless DC motors are in principle a three-phase synchronous machine with electronic rotary field generation. They are excited by permanent magnets .

Synchronous machines with separate excitation often have slip rings as part of a static excitation device . To avoid the slip rings, there is the option of a brushless excitation device .

literature

  • Rolf Fischer: Electrical machines . 14th edition. Carl Hanser Verlag, Munich 2007, ISBN 978-3-446-41754-0 .