Types Of Brushless Motor: With their Applications

In this article, we are going to discuss the Types Of Brushless Motor. This type of electrical motor has no brushes. Brushes are sliding devices that let the electricity flow into the copper coil of the engine.

Brushless motors are of many types. In terms of design it has two types- in runner or inner rotor or out runner and outer rotor. In terms of sensors- sensored and sensorless. In terms of number of poles- single pole and multiple pole. In terms of power signal type- sinusoidal and trapezoidal Brushless motors are there.

Explain inner and outer rotor brushless motor.

Inner rotor and outer rotor are the classifications of brushless DC motors on the basis of design. The magnet used in the motor is the rotor and the winding is the stator. 

Magnets in BLDC help the motor to turn. The stator provides an attractive or repulsive charge towards the magnet and that spins the motor. For the inner rotor BLDC, the rotor is on the inside and the stator is on the outside. For an outer rotor, the design is reverse, i.e. rotor outside and stator inside. 

Medvedev, Stator Winding of a BLDC Motor, size by no, is licensed under CC BY-SA 3.0

Explain sensored and sensor less brushless motors.

It is very clear from the name that this division of brushless DC motors comes from the existence of sensors. If a BLDC has sensors inside the motor then it is sensored, otherwise it is sensorless BLDC.

Sensored BLDC motors have positional sensors that feed positional data to the controller and ensure that the driving pattern properly syncs with the rotor position. A sensorless BLDC has magnets in the rotor and to the motor edge. As the engine speeds up it begins to produce electro-motive energy in the stator coils.

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Explain single and multi pole brushless motors.

Pole in Brushless DC motors refers to the number of permanent magnet poles for the rotor. Single pole BLDC motors are a pair of single-pole brushless motors. Multi pole BLDCs have up to four pair of poles.

Multi pole BLDC motors have multiple pairs of poles, allowing for smooth rotation, improved performance at lower speeds and increased durability. A single pole motor cannot achieve this. Typical applications for such motors include pumps and process control applications where speed is essential.

Types Of Brushless Motor- FAQ

Are brushless motors DC or AC?

Brushless or BLDC motors are technically DC synchronous motors but are called DC motors. So, the obvious question arises: why do we call it DC and is it correct? Well, it is correct as the supply current is DC.

A BLDC motor has a shaft and a rotating rotor. So it has to be AC as the magnetic field should be changing to keep the rotor rotating. If we use DC supply, the rotor will stop after going to a fixed position. BLDC has an inverter that converts the DC supply into AC that is either built-in or external.

What is the fastest brushless motor?

It is quite arguable and ambiguous as to which is the fastest brushless motor. The word “Fastest” can suggest a motor with very high RPM,or a motor that can fly the FPV drones real quick. 

Size, speed and RPM constant are the factors to keep in mind while choosing a brushless motor. We should choose a BLDC with higher KV. KV is RPV or revolutions per volt. If voltage increases, the motor spins quickly. Here’s a list of some brushless motors that runs very fast and efficiently-

  • ‌Traxxas
  • ‌Iflight
  • ‌Crazepony
  • Betafpv
Traxxas Brushless Motor; Image credits: Traxxas.com

BLDC motor applications:

Brushless DC motors or BLDC motors are very important components in electronic devices like Electric vehicles, HVAC, washing machines, compressors, industrial robots, hard drives, CD and DVD players etc.

Following are some applications of BLDC-

  • ‌Industrial use in linear and servo motor, robot actuator, extruder drive motor, CNC machine feed drive etc.
  • ‌Used in home appliances like fans, dryers, pumps, washing machines, blowers etc.
  • ‌Used in the aviation industry for making small drones and also in the healthcare sector.

Why are BLDC motors widely used in industry?

Industrial motors prefer BLDC as main equipment in many devices. They are highly efficient, compact in size and easy to maintain. Nowadays the cost of these motors have also decreased due to the rise in usage.

Manufacturing processes require precise control in motion and stable operation for decent performance in actuation, positioning etc. BLDC produces high torque at low speed that is good for cranes, conveyor belts. Also, some of them are highly durable and can be used for up to 30000 hours. This is why they are heavily used.

Which are the advantages of BLDC motor?

Brushless DC motors are free of commutators or brushes unlike brushed DC motors. Better Longevity, speed and acceleration, less noise and many aspects make BLDC motor a great choice for varied uses. 

Here are the main advantages of BLDC motor-

  • It does not have brushes that restrict speed, produce noise and dust.
  • It can generate more torque at high speed.
  • It has high efficiency and longer lifespan due to lack of friction loss.

Other advantages of BLDC include small size, fast response, better heat dissipation etc.

Why BLDC motors are preferred in high rpm applications?

Brushless DC motors have great speed vs. torque characteristics that makes them suitable for using in high RPM machines. The electromagnetic inference, noise and losses are also less in BLDC motors.

Mechanical power= Torque * speed. For better power we have to increase either of them. In BLDC, when we apply the brake, the torque increases and the speed of the motor goes down maintaining power. Also, the compactness of BLDC allows it to be used in many modern electronic equipment that need high RPM.

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