Power Tools and Brushless Motors - What's the Real Difference Between Brush and Brushless DC Motors?

Update:15 Nov 2019
Summary:

The newest buzz in the power tool community is brushles […]

The newest buzz in the power tool community is brushless motors. Tool users from every trade are wondering how these motors are different, if they really perform better, and if they're really worth all the hype. At this stage in the game, the answers to the these questions are surprisingly positive. Excluding the higher price tag for power tools with brushless motors, the pros and cons list is decidedly imbalanced in favor, of course, of this brushless innovation. In other words, our expectations of these tools are high and our forecast for their future performance and popularity is definitely optimistic.

Construction: How is the Brushless Motor Different?

Brush Motors
As you know, a standard DC brush motor operates with a fairly simple construction. Consisting basically of an armature, the commutator, carbon brushes and a field, the brushed motor in your power tool relies entirely on carbon brushes to transfer electricity from the power source to the motor.

In a nutshell, the armature is a series of electromagnets on a free-spinning shaft, the commutator is connected to the armature by that shaft and acts as a switch to the electromagnet; the brushes are conductive carbon blocks and the field is a ring composed of a series of magnets (a magnetic field). - The brushes press against the commutator from opposite poles of the power source transferring electricity into the commutator (in both positive and negative charges). These charges change the polarity of the electromagnet. The constant switch between poles in the electromagnet alternately pushes and pulls against the conventional magnets in the field to create rotation, and thus, a spinning armature and a functioning motor. The spinning of the motor, though, naturally creates friction against the carbon brushes. This both depletes the brushes promising you'll eventually need to replace them, and also wastes energy within the motor.

Brushless Motors
Brushless motors, on another hand, use a circuit board instead of the carbon brushes and commutator. Conventional magnets surround the shaft and a ring of electromagnets surrounds that magnetic field. The electromagnets are stationary allowing the shaft and magnetic field to spin freely within the electromagnet ring, and because these electromagnets don't spin, electricity can be delivered to them directly. In lieu of the brushes and commutator, the control circuitry now alternates the polarity of the electromagnets.

In other words, a brushless motor doesn't need brushes because it's magnets are positioned differently and because electricity is delivered to the electromagnets directly. Barring unforeseen issues with the circuit board, the brushless motor is super clean and super efficient.

Performance: How Do Brushed and Brushless Motors Measure Up?

Output
As aforementioned, the nature of a brush motor creates friction and drag within the motor. This wastes precious, precious energy. A brushless motor, though, does not necessitate friction and therefore delivers power more efficiently and without waste. In fact, some manufacturers claim that power tools with a brushless motor enjoy 50% longer run-time in between battery charges. Similarly, higher speeds mean higher friction in your motor - this means less overall output and, particularly, less torque. Accordingly, a friction-free brushless motor will deliver greater torque than a standard brushed motor, and because they can also be more compact, brushless technology offers greater power (and higher speeds) from a smaller power tool.

Maintenance
Although a properly used power tool with a brushed motor will give you many, many hours of work before the brushes need replacing, the fact is, every time you run a brushed motor, the brushes wear down. They wear down consistently and will eventually require replacement. Additionally, worn brushes can force the motor's other components to work harder during use; this creates more heat and more wear. - Still, brushed motors are tough and reliable and the pair of brushes in a standard, brush-motored cordless tool may last years before replacement is necessary.

Conversely, and by virtue of being brushless and featuring slightly different components, a brushless tool motor will likely require less overall maintenance. Brushless motor's also tend to run cooler and produce less noise during operation. On another hand, though, while replacing brushes is a simple and inexpensive repair, if your brushless motor requires maintenance, it will likely be a more complex fix and will be more expensive.

Cost
Brush motors are reasonably inexpensive. Brushless motors are more expensive. Period. Even basic power tools with brushless motors are priced like specialty tools.

At this stage in the game, brushless motors are expensive to produce and because the demand for these tools isn't yet comparable to that of brush motor power tools, their production price remains high. As these tools become more mainstream, though (especially with professional tool users and aficionados), the street price of these high-end power tools is likely to decrease. If manufacturers need to produce more of these tools, the price to fabricate them will lower and the final price to consumers should follow suit.

Bottom Line: Are Power Tools With Brushless Motors Really Worth All the Hype?
Are these more complex, more expensive motors really all they're cracked up to be? The short answer is: probably; but it mostly depends on how you use your power tools. If you use a tool only a few times each year or if you are a strictly light-duty user, you probably don't need to upgrade to brushless technology. If you use your tools often or vigorously, though, I think you'll genuinely appreciate the difference.

Ultimately, the hype is appropriate and brushless motor technology is a really exciting step in the evolution of power tools. Whether you choose to lay down a few extra dollars for this new breed of tool is between you and your work-load, but, in either case, I hope you'll share with me some pride in our power tool community that continues to grow and improve and enhance our ability to do what we do.

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