Detailed working principle of brushed DC motor
Brushed DC motors are widely used in applications ranging from toys to push-button car seats. Brushed DC (BDC) motors are inexpensive, easy to drive, and easy to manufacture in a variety of sizes and shapes. This application note discusses the operation of the BDC motor, the method of driving the BDC motor, and the method of interfacing the driver circuit to the PIC chipper.
Detailed working principle of brushed DC motor
Figure 1 shows the structure of a simple BDC motor. The basic components of all BDC motors are the same: stators, brushes and commutators. Each component will be described in more detail later.
Figure 1. Simple double pole brushed DC motor
stator
The stator creates a fixed magnetic field around the rotor. This magnetic field can be generated by permanent magnets or electromagnetic windings. The type of BDC motor is divided by the structure of the stator or the way the electromagnetic winding is connected to the power supply (see the type of stepper motor for different types of BDC motors).
Rotor
The rotor (also called the armature) consists of one or more windings. When these windings are energized, a magnetic field is generated. The magnetic poles of the rotor field will attract the opposite magnetic poles of the stator field, causing the stator to rotate. During the rotation of the motor, the windings are continuously excited in a different order, so that the magnetic poles generated by the rotor never overlap with the magnetic poles generated by the stator. This conversion of the magnetic field in the rotor winding is referred to as commutation.
Brush and commutator
Unlike other motor types (ie, brushless DC motors and AC induction motors), BDC motors do not require a controller to switch the direction of the current in the electrode windings, but mechanically complete the commutation of the BDC motor windings. A split copper bush, called a commutator, is mounted on the shaft of the BDC motor. As the motor rotates, the carbon brush slides along the commutator and contacts the different segments of the commutator. These shards are connected to different rotor windings, so that when the brush is powered by the motor, a dynamic magnetic field is generated inside the motor. It is important to note that the brushes and commutators are the most easily lost parts of the BDC motor due to the relative slip between the two.
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