What is a Brushed DC Motor?
A brushed DC motor is a rotating motor that converts DC electric energy into mechanical energy or converts mechanical energy into DC electric energy with a built-in brush device. Different from the DC brushless motor, the brush device is used to introduce or draw DC voltage and DC current. BDC motor is the basis of all motors, which has the characteristics of fast starting, timely braking, smooth speed regulation in a large range, and simple circuit control.
The basic structural components of a brushed DC motor include stator, rotor, brushes and commutator. The stator and rotor magnetic fields interact to drive the motor to rotate. The types of BDC motors are classified according to the way the magnetic field which is generated in the stator or housing of the motor. The stator magnetic field can be generated by permanent magnets or windings in the stator. What’s more, the stator windings and the rotor windings can be connected in parallel, serial, or mixed. These three types of brushed DC motors are called parallel motors, series motors, and double-excited motors.
The stator of Brushed DC electric motor generates a static magnetic field, which surrounds the armature. The external power source excites the armature magnetic field. There are also two arc-shaped copper plates on the motor shaft of the DC brushed electric motor, which are called commutating plates. When the motor rotates, the carbon brush slides on the commutator. In this way, a rotating magnetic field that is attracted to the stationary magnetic field of the stator can be generated. The current in the armature and stator windings is supplied by batteries or other DC power sources (permanent magnet DC brushed motors do not have stator windings). The battery or DC power supply provides a constant DC voltage. The voltage amplitude determines the speed of the motor, so the DC power supply is a linear excitation source. The most effective way to change the speed of a BDC motor is to use pulse width modulation technology. The pwm technology is to switch the constant voltage source at a fixed frequency. The speed of the motor can be adjusted by changing the pulse width of the pwm signal. And the amplitude of the DC battery level is equal to the average amplitude of the pwm signal.
Brush DC motors are high performance with good starting and speed regulation, which are generally used in occasions with high requirements for starting and speed regulation, such as large reversible rolling mills, mine hoists, elevators, electric locomotives, diesel locomotives, urban trams, subway trains, electric bicycles and large precision machine tools.
