The main difference between brushless DC motor and DC servo motor is from the definition, design principle and essence:

1. Different definitions:

(1) Bushless DC motor is composed of motor body and driver, which is a typical mechatronics product. Brushless motor refers to the motor without brush and commutator (or collector ring), also known as no commutator motor. As early as the 19th motor, the practical motor is brushless form, namely ac rat cage asynchronous motor, this motor has been widely used. However, the asynchronous motor has many insurmountable defects, so that the development of motor technology is slow. The transistor was born in the middle of the last century, so the transistor switching motor was born instead of the brush and commutator. This new brushless motor is called the electronic switching type DC motor, which overcomes the defects of the first generation of brushless motor. (2) DC servo motor, which includes stator, rotor core, motor shaft, servo motor winding commutator, servo motor winding, speed measuring motor winding, speed measuring motor commutator, the rotor core is composed of silicon steel ram stack fixed on the motor shaft.

2. Essentially different:

The brushless DC motor usually adopts the rotor magnetic pole of tile-shaped magnetic steel. After magnetic road design, the air gap magnetic density of trapezoidal wave can be obtained. The stator winding mostly adopts concentrated whole distance winding, so the induction reverse electromotive force is also trapezoidal wave.

The control of brushless DC motor needs position information feedback, which must have position sensor or position sensor estimation technology to form an automatic speed control system. When controlling, the current of each phase is also controlled as far as possible, and the inverter output voltage can be controlled according to the method of brush DC motor PWM.

In essence, the brushless DC motor is also a permanent magnet synchronous motor, and the speed regulation actually belongs to the category of variable voltage frequency conversion speed regulation.

Generally said AC permanent magnet synchronous servo motor has stator three-phase distribution winding and permanent magnet rotor, in the magnetic circuit structure and winding distribution to ensure that the induction electromotive potential wave form is sinusoidal, the external stator voltage and current should also be sine wave, generally provided by AC voltage converter. Permanent magnet synchronous motor control system often adopts automatic control type, also need position feedback information, can use vector control (magnetic field directional control) or direct torque control of advanced control mode.

3. Different configurations:

The difference between DC brush motor and brushless motor is whether there is a commonly used brush-commutator. The direction of the brushed DC motor is always realized by contacting the graphite brush with the annular commutor installed on the rotor. The DC brushless motor feeds back the rotor position back to the control circuit through the Hall sensor, so that it can know the exact time of the phase change of the motor. Most brushless motor manufacturers produce motor motors that have three Hall effect positioning sensors. Because the brushless motor has no brush, so there is no relevant interface, so cleaner, less noise, in fact, no maintenance, longer life.