The advantage of DC motor is also its shortcoming
Brushless DC motor working principle
The stator windings of the motor are mostly made into a three-phase symmetrical star connection, which is very similar to the three-phase asynchronous motor. A magnetized permanent magnet is adhered to the rotor of the motor, and a position sensor is mounted in the motor for detecting the polarity of the rotor of the motor. The driver is composed of power electronics and integrated circuits, and its functions are: receiving start, stop, and brake signals of the motor to control start, stop, and brake of the motor; receiving position sensor signals and forward and reverse signals for controlling the inverse The switching of each power tube of the variable bridge generates continuous torque; the speed command and the speed feedback signal are accepted to control and adjust the speed; provide protection and display, and the like.
DC motors have fast response, large starting torque, and can provide rated torque from zero to rated speed. However, the advantages of DC motors are also its disadvantages, because DC motors must produce constant rotation under rated load. For the performance of the moment, the armature magnetic field and the rotor magnetic field must be maintained at 90°, which is achieved by carbon brushes and commutators. Carbon brushes and commutators generate sparks and toner when the motor rotates. In addition to damage to the components, the use is also limited. AC motors do not have carbon brushes and commutators. They are maintenance-free, rugged, and widely used. However, to achieve the equivalent performance of DC motors, complex control technology can be used. Today's semiconductors are developing rapidly and the power component switching frequency is much faster, improving the performance of the drive motor. The speed of the microprocessor is also faster and faster, and the AC motor control can be placed in a rotating two-axis rectangular coordinate system, and the AC motor's current component in two axes can be appropriately controlled to achieve similar DC motor control and is equivalent to the DC motor. performance.
In addition, many microprocessors have the functions necessary to control the motor in the chip, and the volume is getting smaller and smaller; like analog-to-digital converter (adc), pulse width modulation (pulsewidemodulator, pwm)... Wait. The DC brushless motor is an electronically controlled AC motor commutation, which is similar to DC motor characteristics and has no application missing from the DC motor mechanism.
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