Brushless DC Motor: Construction & Advantages

BLDC motor (also known as brushless direct current motor) is a kind of permanent magnet synchronous motor. BLDC motor replaces the mechanical commutator on the brushed DC motor with an electric commutator, and is powered by a DC power supply through an integrated inverter or switching power supply to generate an AC signal to drive motor. It has the advantages of simple structure, no sparks during commutation, high operational reliability and low maintenance cost, so it has great advantages over traditional brushed DC motors in performance. BLDC motors have high efficiency and good operability, so they are widely used in various transmission industries.

Construction of Brushless DC Motor

The brushless DC motor is composed of the body and the driver. The stator windings of the motor are mostly made of three-phase symmetrical star connection, and the driver is composed of power electronic devices and integrated circuits. The rotor position is fed back to the control circuit through the Hall sensor, so that it can know the exact time of the motor phase commutation. Most brushless motors have three Hall-effect positioning sensors. Since brushless motors have no brushes and no associated interfaces, they are cleaner and less noisy. Brushless motors are maintenance-free and last longer.

The magnetic field produced by the fixed permanent magnets of the DC motor does not move, and it rotates by controlling the magnetic field generated by the coil (rotor), and the number of rotations is changed by changing the voltage. The rotor of the BLDC motor is a permanent magnet, which rotates the rotor by changing the direction of the magnetic field generated by the surrounding coils, and controls the rotation of the rotor by controlling the direction and magnitude of the current leading to the coils.

Advantages of Brushless DC Motor

• High efficiency. The BLDC motor can keep the torque at the maximum value all the time. The maximum torque of the DC motor (brush motor) can only be maintained for an instant during the rotation process, and the maximum value cannot be maintained all the time. If a DC motor (brushed motor) wants to get the same torque as a BLDC motor, it can only use a larger magnet, which is why a small BLDC motor can also be powerful.
• Good controllability, The BLDC motor can get the torque and the number of revolutions you want without any problem. Heat generation and power consumption of the motor can be suppressed by precise control. If it is driven by a battery, the driving time can be extended through careful control.
• Low noise. DC motors wear out over time due to the contact between the brushes and the commutator. The contact part will also generate sparks, especially when the gap of the commutator hits the brush, there will be huge sparks and noise. During operation, the BLDC motor produces less noise.

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