Difference Between Brushed and Brushless Motors (With Table)

A DC motor or a Direct Current motor is an electric machine that works by converting electrical energy into mechanical energy. This process starts when the DC motor takes up electrical energy from the direct current supply and then converts that energy into mechanical energy or rotation. The magnetic fields that are formed are used for bringing motion into the rotor. A DC motor has two types: Brushed and Brushless.

Brushed Motor vs Brushless Motor

The difference between Brushed and Brushless Motors is that a brushed motor uses a two-pole electromagnet as its external rotor, whereas a brushless motor uses a permanent magnet for the external rotor. In a brushed motor, the commutator takes care of the polarity of the electromagnet. While in a brushless motor, three phases of driving coils and a special sensor track the rotor’s position.

A brushed DC motor utilizes wound site coils known as the armature, which functions as an electromagnet. It is used as an external rotor. The direction of current is reversed twice per cycle by the commutator. It also works for reversing the polarity of the electromagnet when it crosses the permanent magnet. This forms the direct current, which later gets converted into mechanical energy.

On the other hand, a brushless DC motor uses a permanent magnet on the rotor. It has an electrical method of turning the rotor. Brush electrodes are not used here, unlike the brushed motor. The working principle of the brushless motor is just the reverse of the former. Electromagnets are used for spinning the motor.

Comparison Table Between Brushed and Brushless Motors

Parameters of Comparison Brushed Motor Brushless Motor
LaunchThe brushed motor got launched in the late 1800s.The brushless motor got launched in the 1960s.
Composed ofA brushed motor contains a physical commutator for the rotor.A brushless motor lacks brushes and runs electronically.
Efficiency It is less efficient because of power losses.It is more efficient.
LifespanIt has a shorter lifespan.Its lifespan is longer.
TorqueTorque is lowered at low voltage.Torque remains higher.
GearingIt requires gearing as it runs very fast.No need for gearing.
FeaturesIt is heavier in comparison.It is lighter and reliable.
PricingIt is cheaper.While it is priced at higher rates.

What is Brushed Motor?

A brushed motor is an electric motor that uses direct current to do the required work. It uses an armature, which functions as an electromagnet. This is used on the external rotor. There is a physical commutator for turning the rotor on. The poles of the electromagnet rub back and forth against that of the permanent magnet, which gradually forms a direct current.

Brushed motors have been in use since the late 1800s. They are highly preferred for commercial and industrial usage. There are four basic components in a brushed motor: the stator, the rotor, brushes, and a commutator. The speed of the motor can be adjusted by changing the voltage amount of the magnetic field strength that is formed within them.

Brushed motors have zinc and pressed steel coating on them, along with a cap made up of plastic, fixed at one of the ends. The coating and cap usually have quite a few holes in order to facilitate airflow although the motor, for preventing it from overheating. Screw holes are also present for fixing the motor in position. The cap also contains connection pins that come in pairs for the power supply connection.

Brushed motors are widely used in households. For example, electric toy cars, electric toothbrushes, bread slices, etc., utilise a brushed motor. In other machines such as cranes, mills, drills, etc., that are required for outdoor activities also make use of this motor.

What is Brushless Motor?

A brushless motor is another type of DC motor. It also uses direct current for its functioning. As the name suggests, a brushless motor does not have brush electrodes. Instead of a physical commutator, it is equipped with an electronic commutator. They follow the reverse working principle of brushed motors. Permanent magnets are used on the rotor, while controllable electromagnets are used for spinning the rotor.

Brushless motors were introduced in the 1960s. They have low maintenance requirements and are highly efficient. The level of control in them is also excellent. They come in two forms: Inrunner, where the stator is on the external part of the rotor, and Outrunner, where the stator is on the internal part of the rotor. As there are no brushes, a small circuit board is used as an alternative.

For the working of the motor, the electromagnet coils are turned on and off consecutively. This is done to magnetize them temporarily for attracting or repelling the permanent magnets. In brushless motors, the amount of torque remains high even at low voltage. Torque is produced by misalignment of magnetic fields of stator and rotor.

Brushless motors have a longer lifespan. They are usually preferred in devices that require continuous motion regularly. Air Conditioners, Washing Machines, Fans etc., are some of the devices that make use of this motor. These motors are also found in electric vehicles.

Main Differences Between Brushed and Brushless Motors

  1. Brushed motors have brushes, while brushless motors do not.
  2. Brushless motors are more efficient in comparison.
  3. Brushed motors are heavier and have a shorter lifespan.
  4. Only the brushed motors require gearing.
  5. Brushless motors are more expensive than brushed motors.
  6. At low voltage, the torque in a brushed motor is lowered, while the torque in a brushless motor remains higher.

Conclusion

A DC motor utilises direct current for its functioning. Two types of DC motors are available. Brushed motors and Brushless motors. They cater to different tasks and are also quite different from each other in terms of working principle, efficiency, speed, pricing etc.

Brushed motors have brush electrodes and a physical commutator. While the brushless motors have an electronic commutator and do not contain brushes. Brushed motors have been longer in the market when compared to brushless motors. The former is best for commercial and industrial use. Brushless motors are used widely for continuously running devices. Choosing one of these motors completely depends on individual needs.

References

  1. https://trs.jpl.nasa.gov/bitstream/handle/2014/42161/NASA_CP-2012-217653.pdf?sequence=1#page=15
  2. https://ieeexplore.ieee.org/abstract/document/4159575/
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