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Views: 0 Author: Site Editor Publish Time: 2025-05-28 Origin: Site
A brushed DC motor is one of the most fundamental and widely used types of electric motors. Known for its simple design, easy operation, and cost-effectiveness, the brushed DC motor is found in countless applications, from household appliances to industrial machines. Understanding how a brushed DC motor works is essential for anyone involved in engineering, automation, robotics, or general electronics.
A brushed DC motor works on the principle of electromagnetic force (Lorentz force). When an electric current passes through a wire placed in a magnetic field, a force is exerted on the wire. In the motor, this force is used to create rotational motion, or torque.
The motor is connected to a direct current (DC) power source. When voltage is applied, current flows through the external circuit, into the motor's brushes.
The brushes, typically made of carbon or graphite, are in constant contact with the rotating commutator. They transfer the current from the stationary part of the motor (stator) to the rotating part (armature/rotor).
The commutator is a segmented, cylindrical structure attached to the rotor. It is connected to the armature windings, which are coils of wire wound around the iron core of the rotor.
As the commutator rotates with the rotor, it changes the direction of current through different coils of the armature at the right moment. This switching is critical for maintaining continuous rotation in one direction.
The current-carrying coils on the armature are placed within the magnetic field produced by either permanent magnets or electromagnetic field coils mounted on the stator.
The interaction between the magnetic field and the current in the coils generates a force (Lorentz force). According to the right-hand rule, this force acts perpendicular to both the magnetic field and the direction of current, causing the rotor to turn.
As the rotor spins, the commutator segments continuously change contact with the brushes. This switches the current direction in each coil just as it passes through the neutral zone, maintaining continuous and smooth rotation.
| Component | Role in Motion |
|---|---|
| Brushes | Deliver current to the commutator from external power source. |
| Commutator | Switches current direction in rotor windings to maintain torque direction. |
| Armature | Houses windings; produces torque when energized and placed in magnetic field. |
| Magnetic Field | Interacts with current in armature to produce rotational force. |
| Shaft | Transfers torque to the external load (e.g., gears, wheels). |
The direction of rotation in a brushed DC motor can be easily changed by reversing the polarity of the applied DC voltage. This reverses the current flow in the armature windings, thus reversing the direction of torque.
Speed in a brushed DC motor is proportional to the applied voltage. Increasing the voltage increases the current, resulting in:
Higher magnetic field strength
Increased torque
Faster rotation
Speed can also be controlled using pulse-width modulation (PWM) or variable voltage supplies.
Low Cost: Inexpensive compared to brushless or AC motors.
Easy Speed Control: Directly proportional to voltage input.
Quick Torque Response: Ideal for start-stop operations.
Brush Wear: Brushes are a friction-based contact point and wear out over time.
Sparking: Contact between brushes and commutator can create electrical noise and heat.
Maintenance Needed: Brushes and commutator require regular inspection and replacement.
Due to their versatility and low cost, brushed DC motors are used in a wide range of applications:
Household Appliances – Blenders, hairdryers, vacuum cleaners.
Toys and Hobby Projects – Remote-controlled cars, robots, drones.
Automotive Systems – Window motors, windshield wipers, seat adjusters.
Industrial Equipment – Conveyor belts, small machinery, automation systems.
Power Tools – Drills, screwdrivers, saws.
The most crucial part of a brushed DC motor is the commutator-brush system, which maintains constant current switching. Without it, the motor would stop once the magnetic force becomes neutral as the rotor turns. The automatic current reversal ensures:
Uninterrupted magnetic interaction
Consistent unidirectional torque
Seamless rotation
The operation of a brushed DC motor is a beautiful demonstration of electromechanical energy conversion. By harnessing the interaction between electricity and magnetism, and using the commutator to continuously switch current, these motors can produce rotational force reliably and efficiently. Their simplicity, control flexibility, and affordability ensure their ongoing importance in both everyday devices and industrial applications.
