A permanent magnet DC motor is a type of DC motor that uses permanent magnets to generate the magnetic field instead of a field coil. Here are some key things to know about permanent magnet DC motors:
- Construction: It consists of an armature winding on a rotor mounted in the strong magnetic field of permanent magnets. The most common type uses iron pole pieces and permanent magnets mounted on the steel stator.
- Commutation: It uses mechanical commutation to direct current to the appropriate segment of the armature winding to initiate rotation. In brushless motors, electronic commutation replaces mechanical brushes.
- Operation: When current passes through the armature winding, it sets up its own magnetic field that interacts with the permanent magnet’s field. This produces a turning force or torque on the armature as per Fleming’s left-hand rule.
- Speed control: The speed can be controlled by changing the current/voltage input to the armature winding. It allows both speed and direction control by reversing current polarity.
- Advantages: High efficiency since it doesn’t require power for the field coil. Compact size, robust construction and simple speed control make it suitable for appliances.
- Applications: Common uses include RC hobby motors, industrial equipment, disk drives, cordless tools, model trains, and robotics. Small PMDC motors are best for precision speed control.
- Limitations: Limited torque density compared to larger DC motors. Commutator and brushes require periodic inspection/replacement to prevent shorts.
Here are some common uses and applications of permanent magnet DC motors:
- Robotics – PMDC motors are widely used in robotics for their precise speed and torque control capabilities. They power actuators, joints, wheels, etc.
- 3D printers – Most desktop 3D printers utilize PMDC stepper motors to accurately position the extruder head and drive the build platform.
- CNC machines – Machines like routers and milling machines often use PMDC stepper motors to precisely position tools.
- Industrial equipment – Things like conveyor belts, mixers, pumps, fans and assembly lines commonly rely on PMDC motors.
- Disk drives – Hard disk and CD/DVD drives employ ultra-small brushless PMDC motors to rapidly spin disks and position read/write heads.
- Appliances – Blenders, food processors, sewing machines, vacuum cleaners use PMDC motors for portability and low cost.
- Power tools – Drills, saws, sanders use compact PMDC motors suited for high torque in a small package.
- Model vehicles – RC cars, boats, planes and hovercraft use small, lightweight PMDC motors.
- Drones – Both civilian and professional drones employ PMDC motors to power propellers due to their size and efficiency.
- Camera/optics – PMDC stepper motors are ideal for smoothly controlling shutter speeds, lenses, mirrors in cameras.
- Home automation – Devices like garage door openers, security cameras, automated blinds rely on inexpensive PMDC motors.