Structural principle analysis of brushless DC electric motor

- Oct 16, 2019-

In the field of generators, brushless DC electric motor are electronically commutated low-power DC motors that replace traditional contact commutators and brushes with electronic switching devices. It has the advantages of high reliability, no commutation spark, low mechanical noise, etc. It is widely used in production equipment, electronic instruments and automated office equipment.

The brushless DC electric motor is composed of a permanent magnet rotor, a multi-pole winding stator, a position sensor and the like. The position sensing commutates the current of the stator winding in a certain order according to the change of the rotor position (ie, detecting the position of the rotor pole relative to the stator winding, and generating a position sensing signal at the determined position, after being processed by the signal conversion circuit To control the power switch circuit, the winding current is switched according to a certain logic relationship). The operating voltage of the stator windings is provided by an electronic switching circuit controlled by the position sensor output.

Brushless DC electric motor position sensors are available in magnetic, photoelectric and electromagnetic types.

A brushless DC electric motor using a magnetic sensitive position sensor, the magnetic sensing element (such as a Hall element, a magnetic sensitive diode, a magnetically sensitive diode, a magnetoresistor or an ASIC) is mounted on the stator assembly. To detect the change of the magnetic field generated when the permanent magnet and the rotor rotate.

A brushless DC electric motor using a photoelectric position sensor has a photoelectric sensor device arranged at a certain position on the stator assembly, and a light shielding plate is mounted on the rotor, and the light source is a light emitting diode or a small light bulb. When the rotor rotates, the photosensitive components on the stator will intermittently generate pulse signals at a certain frequency due to the action of the visor. A brushless DC electric motor using an electromagnetic position sensor is provided with an electromagnetic sensor component (for example, a coupling transformer, a proximity switch, an LC resonance circuit, etc.) on the stator assembly. When the position of the permanent magnet rotor changes, the electromagnetic effect will cause the electromagnetic sensor. A high frequency modulated signal is generated.