What Are The Differences Between Sensored Brushless Motor And Sensorless Brushless Motor

What is a Sensored Brushless DC Motor?

A sensored brushless DC motor is an advanced type of electric motor that incorporates sensors for enhanced control and performance. The sensors typically employed in sensored BLDC motors are Hall effect sensors. Hall sensors are able to accurately determine the real-time position of a brushless motor rotor by measuring the strength and direction of nearby magnetic fields. This provides critical positional feedback to the motor control system, enabling the system to precisely adjust the current and magnetic field as needed for efficient, stable operation. Brushless motors with Hall sensors exhibit enhanced performance in conditions such as starting, braking and low-speed operation.

In addition, hall sensors play a key role in providing speed information. By monitoring the pulse signals output from Hall sensors, motor control systems can accurately measure the speed of the motor. This is important for applications that require real-time speed adjustments!

What Is A Sensorless DC Motor?

The term "sensorless" in sensorless brushless refers to the absence of Hall sensors. In the absence of direct feedback, a sensorless brushless motor determines the rotor position indirectly. Various methods, including the back electromotive force, inductance, flux linkage, high-frequency pulse, and intelligent techniques, can be employed. The most prevalent method is the back electromotive force approach.

During startup, a sensorless brushless motor lacks knowledge of the rotor's magnetic pole orientation. It initiates motion by randomly adjusting the current, akin to a guessing process. Eventually, the rotor begins to rotate, allowing the motor to calculate its position based on current changes and subsequently control the current and direction.

In contrast to sensored brushless motors, which utilize sensors to ascertain rotor magnetic pole orientation instantly upon startup, sensorless brushless motors lack this information. As a result, they must adapt by adjusting current randomly until the rotor starts to move. This "guessing" strategy eventually allows the motor to calculate rotor position, facilitating subsequent control of current and direction.

Unlike sensored motors, sensorless brushless motors exhibit silence at low speeds since they don't produce a continuous sound associated with small currents. This distinction explains why sensored motors often emit a constant noise at low speeds, while sensorless brushless motors do not.

Applications Differences

The application differences between Sensored Brushless DC (BLDC) motors and Sensorless Brushless DC (BLDC) motors are notable and cater to specific requirements in various industries. Sensored BLDC motors, equipped with position sensors like Hall effect sensors, are often preferred in applications demanding precise control, especially at low speeds. Industries such as robotics, medical devices, and aerospace, where accuracy and reliability are paramount, benefit from the enhanced performance of sensored BLDC motors. The sensors provide real-time feedback on the rotor's position, enabling the controller to make rapid and accurate adjustments, resulting in smoother operation and improved efficiency. However, the additional sensors contribute to higher costs and increased complexity.

On the other hand, Sensorless BLDC motors are favored in applications where simplicity, cost-effectiveness, and reliability are critical factors. These motors employ advanced algorithms to estimate the rotor position without relying on external sensors, making them suitable for applications like household appliances, HVAC systems, and power tools. The absence of additional sensors reduces the overall complexity and cost of the motor system, making sensorless BLDC motors a practical choice in scenarios where precise position control is not a primary concern, and a more straightforward and cost-effective design is preferred.