Here are a few key things to know about brushless DC motors:
- Construction: BLDC motors do not have physical brushes like brushed DC motors. They have a stationary stator (outer shell) with coils that generate a magnetic field, and a rotating rotor with permanent magnets.
- Commutation: The position of the rotor magnets is sensed electronically using Hall effect sensors or encoder feedback. This allows for electronically commutating the coils to generate torque.
- Efficiency: BLDC motors are more efficient than brushed DC motors since there is no mechanical friction or wear from the brushes. They can achieve efficiencies up to 95%.
- Speed control: Electronic commutation allows for precise control over motor speed by varying the timing and sequence of current in the coils. Speed can be adjusted over a wide range.
- Applications: Commonly used in devices where efficiency, precision control and long life are important – such things as electric vehicles, factory automation equipment, disk drives, drones, robots, and more.
- Power output: Power ratings range from milliwatts for small fans/motors to multi-horsepower for electric vehicle drivetrains. Torque constant over a wide speed range.
- Maintenance: BLDC motors have no brushes to replace, increasing their lifespan for many thousands of hours of operation with little maintenance required.
- It consists of a rotor with permanent magnets and a stator with wound coils. The rotor may have surface mounted or internal magnets.
- The coils are arranged in phases and powered sequentially to create a rotating magnetic field. Commutation is done electronically via rotor position sensors and switching circuits.
- With no windings or contacts on the rotor, it rotates unhindered at very high speeds. Neodymium magnets allow high power density.
- The switching of the stator field is timed such that the rotor magnets are attracted and pushed by the rotating field at all times.
- Speed control is achieved by varying the stator voltage and frequency. This controls the strength and speed of the rotating magnetic field.
- Has very high speeds capability (over 10,000 rpm) and high efficiency. Almost identical torque-speed curve to brushed DC motors.
- Requires electronic commutation using Hall effect or optical encoders to sense rotor position and energize the windings accordingly.
- Used in computer hard drives, drones, electric vehicles, CNC machines, robotics, industrial machinery and other high-performance applications.