Brushed Motor

A brushed motor is an easy-to-drive, low-cost DC motor often driven by batteries. The electric motor uses brushes to provide power to an armature coil sitting between permanent magnets that create the magnetic field. The current though the brush to the coil drives the rotor and is used for motors up to a horsepower. As the armature rotates, the stationary brushes come into contact with different sections of the rotating commutator and so wear out over time.

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• Working principles

  • Brushed motors generally operate at low speed and can be driven by a simple pulse width modulation (PWM) controller to vary the voltage supplied to the motor to control the speed in one direction and provide the torque for the motor drive. If a bidirectional motor drive is needed, for example for an electric car window or as a servo in an industrial automation application, an H-bridge can be used alongside the PWM controller.

    For low power applications, the motor control is integrated into the motor along with embedded gate drivers, power transistors, protection functions, current sensing and even DC-DC converters.

    For high power applications, discrete low-voltage power MOSFETs and gate drivers are used separately to the motor to implement the H-bridge.

    Using the brush reduces the lifetime of the motor. A brushless motor in comparison has a significantly longer lifetime and more controllability.

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