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What is the difference between a brushless motor and a brushed motor? Explaining the features of Adamant Namiki brushless motors.

What is the difference between a brushless motor and a brushed motor? Explaining the features of Namiki brushless motors.
   Last Modified:    Published: 2021/06

What is a brushless motor?

Brushless motors are motors in which the mechanical contact parts, such as commutators and brushes, have been removed.

Previously, the commutator was used mechanically to reverse the plus and minus, but this had the disadvantage of wearing out the commutator, making it difficult to extend the service life.

With the widespread use of semiconductors, electronic circuits were able to replace commutators electronically, enabling the removal of brushes and commutators from motors.

This has resulted in brushless motors with a longer life than mechanical commutators.

Find more information about our brushless motors here:

Differences between brushless motors and brushed motors

1: Heat dissipation

In a coreless motor with a brush, there is a gap (layer of air) between the rotating coil and the motor housing, so heat generated by energization is not easily transferred to the outside.
In contrast, in brushless motors, the magnet rotates and the coil is fixed in close contact with the outer core side, so the heat from the coil is easily transferred to the outside, resulting in high-efficiency heat dissipation.
If the temperature inside the motor rises too much, the magnet may be demagnetized and performance may deteriorate.
For this reason, brushless systems with high heat dissipation are more advantageous for higher power uses.

2: Large current/high power

In brushed motors, the commutator on the rotor side and the brush on the stator side slide while energizing. If a large current is applied, the electrical contact may melt and fail, so there are limitations on power input.
In brushless motors, the driver circuit controls the externally-energized coil, so there is no contact point, and this along with high heat dissipation means a large current can be applied to the motor.

3: Mechanical noise

Brushed motors

Brushed motors generate a mechanical sliding noise due to the contacts rubbing against each other. In addition, when the contacts switch with rotation, sparks are generated at the contacts, which causes electrical noise.

Brushless motors

Brushless systems have no contacts and therefore no noise source.

Moving magnet: In brushless motors the magnet rotates. brushless motors have Stator coil and Magnet rotor.
Moving coils: Generally, in brushed motors the coil rotates. Brushed motors have brush, commutator and commutator coil rotor

Brushless motors have better heat dissipation, higher maximum rotation speed, longer life, and less noise than brushed motors. However, unlike brushed motors, which can be operated simply by connecting them to a DC power source, brushless motors need a control circuit for operation. Selection of the appropriate control circuit depends on whether the motor has a sensor that detects rotor position.

Brushless servo driver (Reference): Motor Drive Circuit SSD06-R5A / SHSD24-01A

Characteristics of Adamant Namiki brushed motors

Compared to the typical slot armature of brushed motors (with iron core), our company's coreless brushed motor does not have armature windings in the slots, so the leakage inductance of the coil is small and the rectification is good.
Since there is little variation in magnetic resistance, cogging (torque pulsation caused by the iron core) is reduced, which means the motor produces very little electrical noise.

Characteristics of Adamant Namiki brushless motors

Non-contact motor means extremely high power and a long service life, ensuring high reliability.

Adamant Namiki's brushless motor has a slotless structure, without slots in the stator.
Such slots (gaps in the magnetic core) can cause cogging (rotation pulsation) because the magnet attracts the convex portion between the slots.
This cogging affects vibration and noise, as well as rotation accuracy and smoothness.
Adamant Namiki's brushless motors have cup-like coils installed in the core, and the rotor's magnet is placed inside.
That way, the coil and magnet are subjected to uniform magnetic attraction regardeless of the position, thus enabling smooth rotation without cogging.
Our motors are suitable for applications such as robots and medical equipment that are particularly sensitive to factors such as torque and life-span.

Product lineup

At Adamant Namiki, we take advantage of the technology we have cultivated through the development of the world's smallest motors, and we offer a standard lineup of brushless motors starting from φ4mm.
The compactness, torque, service life, quietness, and low-vibration of our brushless motors offer solutions for applications that require high performance in a limited space, such as portable equipment, communication robots that require delicate movements, special astronomical telescopes that require actuators to be placed in a narrow pitch, and joint actuation in robotic hands.

Extending the life of brushless motors

The B4S series motor in our brushless motor lineup is a high-torque motor employing a 4-pole magnet.
By changing the magnet from the usual 2 poles to 4, the effective magnetic flux area is increased, improving the torque constant and reducing the current consumption.
Improved mechanical time constant further increases startability and responsiveness.
The B4S series also uses ball bearings as standard, and high torque is also supported by the reliability.


Reference: Introduction to Motor Technologies. Yuji Akiyama, Kogyo Chosakai Publishing Co., Ltd. 1999

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