Ten important facts and trends in motor control
Previously, we did a series of popular science about motors (see the end of the article for details). Now, based on our understanding, we would like to share with you the ten most important facts and development trends in the field of motor control:
Integration is taking over the motor control market due to technological advancements. Brushless DC motors (BLDC) and permanent magnet synchronous motors (PMSM) in a variety of sizes and power densities are rapidly replacing motor topologies such as brushed AC/DC and AC induction.
Brushless DC motors/permanent magnet synchronous motors have the same mechanical structure, except for the stator winding. They have a different stator winding geometry. The stator is always opposite the motor magnets. These motors provide high torque at low speeds, making them ideal for servo motor applications.
Brushless DC motors and permanent magnet synchronous motors do not require brushes and commutators to drive the motor, so they are more efficient and reliable than brushed motors.
Brushless DC motors and permanent magnet synchronous motors use software control algorithms instead of brushes and mechanical commutators to drive the motor.
The mechanical structure of brushless DC motors and permanent magnet synchronous motors is simple. The motor has an electromagnetic winding on a non-rotating stator. The rotor is made of permanent magnets. The stator can be inside or outside and is always on the opposite side of the magnet. But the stator is always the fixed part, and the rotor is always the moving (rotating) part.
Brushless DC motors can have 1, 2, 3, 4 or 5 phases. Their names and drive algorithms may be different, but they are all brushless in nature.
Some BLDC motors have sensors that help obtain the rotor position. Software control algorithms use these sensors (Hall sensors or encoders) to assist in motor commutation or motor rotation. These sensored BLDC motors are needed when the application needs to start under high load.
If the brushless DC motor does not have a sensor to obtain the rotor position, mathematical models are used. These mathematical models represent sensorless algorithms. In sensorless algorithms, the motor is the sensor.
Brushless DC motors and permanent magnet synchronous motors offer some important system advantages over brushed motors. They can drive the motor using electronic commutation schemes, which can improve energy efficiency by 20% to 30%.
Many products today require variable motor speeds. These motors require pulse width modulation (PWM) to change the motor speed. Pulse width modulation provides precise control of motor speed and torque, allowing variable speeds.
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