Brushless DC motors (BLDC) have generated much interest among manufacturers because they are becoming the preferred option in a growing number of applications, especially in motor control. BLDC motors surpass brushed DC motors in various ways, along with the capacity to perform at high speeds, remarkable efficiency, and better heat dissipation. Modern drive technology, such as actuation drives, robotics, machine tools, computer peripherals, electric propulsion, and electrical power generation, all rely on them. Because of the development of sensorless technology concerning digital control, these motors have proven highly efficient in terms of total system cost, size, and dependability.

What is an Outrunner Brushless DC Motor?

A Brushless DC electric motor with an outrunner stator has the stator located outside the rotor. (Doncen Motor)This arrangement makes better use of space and produces a more excellent power-to-weight ratio than other brushless motor models. Outrunner BLDC motors are shorter than inrunner BLDC motors, and they provide a cost-effective alternative for large series applications. Permanent magnets are installed on the rotor housing, which spins around the internal stator with the windings in these motors. Outrunner motors have less torque ripple than inrunner motors because the rotor has more inertia.

Outrunner BLDC Motor Construction

Outrunner BLDC motors come in a range of physical shapes and sizes. In this configuration, the rotor is on the outside. The stator windings are contained in the core, whereas permanent magnets are placed in the rotor, encircling the stator. Depending on the stator windings, these motors can be single-phase, two-phase, or three-phase. On the other hand, three-phase BLDC motors having permanent magnet rotors are the most common. In a standard DC motor, a commutator-brushes configuration aids in achieving unidirectional torque.

On the other hand, a brushless DC motor does not have a commutator or brushes. To generate unidirectional torque, a linked inverter/switching circuit is employed. Because of this, these motors are also known as “electronically commutated motors.”

A BLDC motor, like any other dc motor, has two primary components: a stator and a rotor. On the rotor of a BLDC motor, permanent magnets are placed, and the stator is twisted for a certain number of poles. The stator winding is also linked to a control circuit. The stator assembly frequently includes the inverter/control circuit or controller. The significant structural difference between a brushless and a conventional dc motor is this. The stator winding receives a three-phase frequency-controlled feed from a traditional controller. Logic control circuits regulate the collection, which energizes specified stator poles at a given moment.

Working on Outrunner Brushless Motor

A BLDC motor works on the same principle as a regular DC motor. The magnet encounters an equal and opposite force due to the reaction force. The current-carrying wire is stationary in a BLDC motor while the permanent magnet moves. An Outrunner BLDC motor’s stator windings are linked to the control circuit (an integrated switching circuit or inverter circuit). The control circuit triggers the required windings in a particular order, causing the stator to rotate at the appropriate times. The permanent magnets on the rotor try to align with the stator’s active electromagnets, and once they do, the next electromagnets are energized. As a result, the rotor continues to spin.

Outlook for Outrunner BLDC Motor in Markets

Brushless motors have grown in popularity due to their outstanding efficiency, low noise, extended life, and other benefits.

The global brushless DC motor market size was valued at $9.8 billion in 2019, and it is expected to grow at a CAGR of 7.0 percent between 2020 and 2025, achieving $14.1 billion by 2025. In 2019, the Asia-Pacific region was expected to be the largest market for brushless DC motors, accounting for approximately 38% of the worldwide market.

The brushless outer rotor motor outperforms the inner rotor motor in terms of space and weight. The brushless outer rotor brushless motor has a hefty price tag. However, industry feedback indicates that the brushless external rotor market is rapidly growing each year.

Brushless VS Brushed DC Motors

  • Due to mechanical wear, brushes must be changed regularly. A brushed DC motor may thus be maintained on a regular basis. The bushes conduct electricity to the commutator, causing it to ignite. Brushes restrict the armature’s maximum speed and the number of poles it may have. A brushless DC motor eliminates all of these disadvantages. An electronic control circuit switches the stator magnets and keeps the motor spinning in a brushless DC motor. As a result, a BLDC motor’s lifespan may be shortened.
  • BLDC motors outperform brushed motors in terms of efficiency, reliability, and lifetime, as well as having less sparking and considerably less noise, higher torque per weight, and other benefits.

Difference between Outrunner and Inrunner Motors

Compared to an inrunner motor, the air gap surface of an outrunner motor is significantly bigger. In other words, the electromagnetic field lines flow via a significantly wider surface area from the rotor to the stator. More electromechanical force is created this way.

Furthermore, because the force is generated further from the center of rotation, the torque arm of an outrunner motor is longer. As a result, more torque is produced via a more extensive air gap surface area and a more extended torque arm. As a result, outrunner motors with the same construction volume may reach substantially greater torque levels than inrunner motors.

Applications of Outrunner BLDC Motors

Brushless DC Motors (BLDC) are engineered to meet many of the exact exacting requirements of brushed DC motors. Because they need a sophisticated control circuit and are costly, they have not yet wholly overtaken brushed DC motors, especially for low applications. Despite this, BLDC motors are extensively employed in a variety of applications: 

  • Quiet operation is required by consumer electronics (computer hard drives, tiny cooling fans, CD/DVD players, and so on) and modern appliances, air conditioners, a (washing machines, and so on).
  • Electric vehicles with BLDC motors include electric and hybrid automobiles and electric motorcycles.
  • Robotics, industrial automation, and motion control systems are just a few of the fields used.


Outrunner Brushless motors are used in almost every part of our lives, and their prevalence is growing. These motors astonish us with their small size, efficiency, and dependability in various settings, from the house to the office.

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