Brushless DC Motor Control Key Terms - Glossary

We always try our best to not use excessive terminology but there are obviously some key terms that are required for a good understanding of brushless DC motor control. 

Here are the first 30 we could think of... (let us know if you need any more explaining);

Brushless DC Motor (BLDC): A type of synchronous motor powered by direct current (DC) electricity via an inverter or switching power supply which produces an AC electric signal to drive the motor.

Stator: The stationary part of the motor that generates a rotating magnetic field, typically containing the windings.

Rotor: The rotating part of the motor that includes permanent magnets and rotates inside the stator.

Hall Effect Sensors: Sensors used to detect the position of the rotor in a BLDC motor by measuring the magnetic field intensity.

Electronic Speed Controller (ESC): A device that regulates the speed and direction of a BLDC motor by controlling the power delivered to the motor's windings.

Pulse Width Modulation (PWM): A modulation technique used to encode a message into a pulsing signal, commonly used for controlling the speed of the motor.

Commutation: The process of switching the current in the motor windings to generate continuous rotation. In BLDC motors, this is typically done electronically rather than mechanically.

Back Electromotive Force (Back-EMF): The voltage generated by the motor as it rotates, which opposes the applied voltage and is used for sensorless control methods.

Sensorless Control: A method of controlling a BLDC motor without using position sensors, relying on the back-EMF to estimate the rotor position.

Field-Oriented Control (FOC): An advanced method of motor control that uses real-time feedback to control the stator currents in such a way that they are orthogonal to the rotor magnetic field, optimizing torque and efficiency.

Torque Constant (Kt): A constant that relates the torque generated by the motor to the current passing through its windings.

Voltage Constant (Ke): A constant that relates the back-EMF generated by the motor to the angular velocity of the rotor.

DC Link: The intermediate DC voltage link in a motor drive system, typically found between the rectifier and the inverter.

Inverter: A power electronic device that converts DC voltage from the power supply to AC voltage needed to drive the motor.

Phase Current: The current flowing through each phase winding of the motor.

Cogging Torque: The torque due to the interaction between the permanent magnets of the rotor and the stator slots, causing uneven motion.

Torque Ripple: Variations in the torque output of the motor, often caused by cogging or non-ideal commutation.

Duty Cycle: The ratio of the time a signal is on to the total time period, used in PWM to control motor speed.

Synchronous Motor: A type of motor where the rotation of the shaft is synchronized with the frequency of the supply current.

Permanent Magnet: Magnets that are used in the rotor of a BLDC motor to create a magnetic field without the need for external excitation.

Hysteresis: The lag between the applied magnetic field and the resulting magnetization, affecting the performance of the motor.

Torque Control: The method of controlling the torque output of the motor, usually involving feedback from torque sensors or estimations based on current measurements.

Speed Control: The method of controlling the rotational speed of the motor, often achieved through adjusting the input voltage or PWM duty cycle.

Position Control: The method of controlling the position of the motor shaft, typically used in applications requiring precise movement.

Encoder: A sensor that provides feedback on the position and speed of the motor shaft, used for accurate control in closed-loop systems.

Closed-Loop Control: A control system that uses feedback from sensors to adjust the motor operation in real-time, ensuring accurate performance.

Open-Loop Control: A control system that operates without feedback, relying on predefined commands to control the motor.

Sinusoidal Commutation: A method of controlling a BLDC motor by applying sinusoidal waveforms to the motor windings, resulting in smoother and more efficient operation.

Trapezoidal Commutation: A simpler method of controlling a BLDC motor using trapezoidal waveforms, resulting in more torque ripple compared to sinusoidal commutation.

Motor Efficiency: The ratio of mechanical output power to the electrical input power, indicating how effectively the motor converts electrical energy into mechanical energy.


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