Direct current (DC) motors are electrical motors invigorated by direct current. Distinguished by their capability to attain high velocity and furnish potent initial torque, these motors can be classified into multiple categories. In this article, we impart a straightforward explication of the brushed DC motor and its mode of operation.
The Various Types of DC Motors
Electric motors have several variants, each defined by their architecture and driving mechanism. AC motors operate on alternating current, stepper motors execute rotation in fixed increments with each pulse of electricity, while DC motors are fueled by direct current. DC motors hold advantages, notably their ability to attain high speed and furnish potent starting torque.
Brushed and brushless motors are the two main categories within DC motors. The function of a brushed DC motor hinges on the mechanical interaction between the commutator and brushes. In contrast, brushless DC motors, bereft of a commutator and brushes, rely on an electronic control mechanism through a drive circuit. Brushed DC motors can function without a drive circuit in scenarios where speed control is unnecessary. The significant features of DC motors include:
High-speed operation capability
- Potent starting torque
- Control over motor speed and torque via voltage
- Segmenting Brushed DC Motors into Permanent Magnet Motors and Electromagnet Motors
- Brushed DC motors can be subdivided into two groups depending on the type of magnet implemented.
Permanent Magnet Motors
These are the most prevalent form of electric motor globally, finding applications in toys, models, and auxiliary motors in automobiles. They employ a permanent magnet to produce the magnetic field and incorporate a permanent magnet stator along with coils for the rotor.
Electromagnet Motors
These motors generate a magnetic field through an electromagnet. Their further classification can be divided into distributed-winding, series-wound, and separately-excited motors based on the mechanism behind field winding and armature interlinkage. They find widespread usage, ranging from medium-sized motors of approximately 1 HP to considerably large motors.
The application and the requisite motor size govern the selection of motor type.
The Working Mechanism of Brushed DC Motors
Now, let’s dive into the operation of brushed DC motors. These motors house wound coils within the rotor, encircled by magnets in the stator. Both ends of a coil are connected to the commutator, which connects to electrodes termed brushes. This arrangement results in the flow of direct current power through the brushes and coil while they remain in contact with the commutator.
However, the rotation of the coil occasionally brings it to a position where it loses contact with the brushes and commutator, interrupting the current flow. Yet, the coil continues to rotate due to its momentum until it reestablishes contact, restoring current flow through a different coil.
This recurrent alternation of current flow keeps the brushed DC motor in rotation. They function on direct current, and the applied voltage can conveniently control their speed.
The Perishability of Brushes and Commutators
As highlighted, brushed DC motors, despite their simplistic structure, can deliver high initial torque and operate at high speeds. They are user-friendly, capable of running without a drive circuit if speed control is not a requirement. Nonetheless, these motors have certain shortcomings, namely:
- Predisposition to generate electrical and acoustic noise
- Short lifespan coupled with the need for routine maintenance
The ceaseless contact between the brushes and commutator while the motor rotates generates electrical and acoustic noise. The friction-induced wear and tear caused by this continual interaction gradually degrade these components. The erosion of the metal brushes reduces their contact with the commutator, impairing their ability to conduct electric power. Consequently, the motor’s functioning deteriorates. This wear and tear elucidate why brushes and commutators are perishable components, necessitating routine inspection or replacement.
The Essentiality of Maintenance in Brushed DC Motors
There are two divisions of DC motors, i.e., brushed and brushless DC motors. Brushed DC motors function as the coil rotates within the surrounding magnets, causing the contact between the commutator and brush to switch, thereby altering the current flow through the coil. This enables the brushed DC motor’s operation.
Despite its simplistic structure, the continuous interaction between the brushes and the commutator during the motor’s rotation causes wear and tear. This necessitates routine maintenance to replace the worn-out components.
