T.G. Wilson and P.H. Trickey invented the Brushless electric motor in 1962. They both explained the problems they intended to solve with their invention. Brushless motors have a long-standing history as permanent magnetic synchronic motors, and they’ve mostly been used in industrial applications because of the difficulty in starting a changing speed.
Often referred to as Brushless DC Motors (BLDC Motors), these motors have evolved over time, merging the characteristics of traditional DC motors with the benefits of brushless technology.
However, in recent years, brushless motors have seen significant development across a wide range of fields due to the advancements in strong permanent magnets. Let’s delve into the world of brushless electric motors, their different models, and the ideal applications they need to be employed for.
Mechanism of a Brushless Electric Motor
The brushless motor relies on two parts to function properly; the rotor and stator–the rotor holding the permanent magnets, and the stator holding the copper coils that act as electromagnets once current passes through it. Brushless motors come as either in-runners or outrunners. With runners, the rotor rotates within, while the stator is located outside, and for outrunners, the rotor rotates outside of the stator.
Once currents get to the coil of the stator, the stator becomes an electromagnet with North and South poles. If the polarity of the electromagnet matches with the permanent magnet it faces, it causes the like-poles to repel, and the rotor spins. When the current is maintained, the rotor will spin only for a while, and stop once opposite electromagnets and the permanent magnets align.
This is why the current is always delivered as a three-phase signal, so the configuration is set in a way that constantly changes the polarity of the electromagnets, so the rotor will keep turning.
Note that the motor spins at the same speed as the frequency of the three-phase signal. So, if you want the motor to move at a faster speed, you need to increase the frequency. If you are using a remote-controlled vehicle, you can increase the speed by increasing the throttle.
Then there’s the disk rotor type as well. In this construction, the stator is formed by mounting the sensors of the magnetic pole and the windings on the circuit board. The tabular permanent magnets are positioned on the rotor’s surface facing this stator, and that’s why this type of rotor is usually thin. It’s mostly used to maintain a fixed speed with a light load.
You can see the disk rotor in hard disk drives, and maybe applications that require small spaces.
Types of Brushless Electric Motors
Brushless motors are of many variations, and knowing their common specifications will help you understand better when choosing the right motor type for your job.
Sensored and Sensor-less Brushless Motors—Based on the Use of Sensor
A brushless motor either has a sensor or it doesn’t; it’s as simple as that. Sensored brushless motors have positional sensors that send information to the controller to ensure that the driving pattern is in sync with the rotor’s position. A sensor-less brushless motor has magnets positioned in the rotor and the motor edge. Once the engine speeds up, it generates electro-motive energy in the stator coils.
Single and Multi-Pole Brushless Motors—Based on the Number of Poles
Poles are the number of permanent magnet poles located in the rotor of a brushless electric motor. Single-pole motors refer to motors with a pair of single poles, while multi-pole motors can have more than four pairs of poles.
Brushless motors with multi-poles have a smoother operation, improved performance, and better durability; all of which cannot be achieved with a single-pole brushless motor. Multi-pole brushes are used for applications where speed is of utmost importance, like pumps.
Sinusoidal and Trapezoidal Brushless Motors—Based on Type of Power Signal
In sinusoidal brushless motors, the motors use a duty cycle signal that gives off a sinusoidal shape–hence the name.
Here, the controller tries to supply power to all the stator windings with a current that assumes a smooth sinusoidal curve. The downside of a sinusoidal brushless motor is that, while it offers a smooth performance, it does so at a low speed. When forced to operate at higher speeds, the torque reduces, hence it’s ideal for applications that require low speeds.
A trapezoidal brushless motor uses a power signal that creates a trapezoid shape, and it’s a simpler commutation method than the sinusoidal. The commutation method of a trapezoidal brushless motor involves supplying power to one pair of terminals at a time, making sure the third terminal is disconnected.
Regardless of the simplicity, it still causes a torque ripple effect, thereby making the operation less smooth, most especially at lower RPM. But at higher RPM, they perform a lot better than the sinusoidal motors, and that’s why they are more suited for high-speed situations.
Interesting Applications of Brushless Electric Applications
We’ve established that brushless motors are highly efficient and have precise control. So, the next question is, “What are they good for?” Let’s delve into the applications of brushless motors.
For Drones
Brushless motors are ideal for drones. It’s lightweight, efficient, and has a high-speed range and torque capabilities–all of which are needed for UAVs. The beauty of it all is that there are specific models of brushless motors designed especially for hobby drones. This allows manufacturers to test out different models and determine which ones have the best performance.
You don’t even have to conduct regular maintenance, plus it usually costs way less to replace the motor than going through the stress of repairing it. For professional drones, there are brushless motors with large capabilities, designed to generate greater power and thrust. These motors are the forerunners in the electric revolution happening in the transportation industry. There are different types of drones–varying sizes, styles, functions, and power sources.
For RC Cars
Brushless motors rotate at very high RPM and they deliver brilliant bursts of speed, making them perfect for RC vehicles.
Characteristics of RC motors — motor size and power rating will vary based on the model. Some RC cars have nitro motors that give a long run time, but there’s the drawback of buying gas. However, brushless motors have an acceleration advantage, hence they are better suited for racing.
Industrial Engineering
Due to their high torque and longevity, brushless motors are useful for industrial engineering processes. You can find them in linear motors and CNC machines, and they are even used as actuators to facilitate movements in industrial robots.
Cordless Power Tools
Brushless motors run on rechargeable batteries, so you can easily use them in cordless applications that need high RPM but minimal weight. This is one area where both brushless and brushed are at a draw; so, when deciding based on the cordless factor, consider the price and frequency.
In-Home Appliances
Brushless motors are popular in many home appliances like coffee machines, printers, vacuum cleaners, and hair dryers. The models of brushless motors used in these appliances are low-weight and high efficiency. Many of these devices are produced with the best quality of brushless motors to ensure durability and unbeatable performance.
Why Brushless Motors? Are They The Best?
The decision to opt for a brushless motor depends on how you want to use it. It’s common knowledge that brushed motors aren’t suited for high RPM applications, meaning brushless motors are a better choice. Brushless motors also have a solid advantage in their torque and are best for applications with high usage. So, in a nutshell, brushless offers ease of use and more advantages than other types of motors.
Frequently Asked Questions
What Brushless Motor is Considered the Fastest?
It’s quite arguable as to which type of brushless motor is termed the fastest. Fastest is relative; it can mean a brushless motor that can fly FPV drones quickly or a motor with extremely high RPM. Brands of brushless motors that operate very fast and efficiently are Crazepony, Iflight, and Betafpv.
Why Are Brushless Motors Commonly Used In Industry?
Brushless motors are widely used in industrial motors because they are efficient, portable, and require minimal maintenance. Plus, there has been a slight decrease in price because of the rise in usage.
Why Are Brushless Motors Preferred in High RPM Applications?
Brushless motors have a great speed that makes them ideal for RPM machines, and their electromagnetic inference and noise are lesser than other motors.
Conclusion
Brushless electric motors have different benefits when employed in specific applications. They are termed zero maintenance devices that have a long lifespan, plus their small size and fast response make it a more desirable option. Brushless motors are found in almost every aspect of our daily activities, and you don’t need a background in electromagnetism to fully understand the fascinating aspects of brushless electric motors.
Related reading: Applications of DC Motors
