Brushed or Brushless Motors?

 

Introductions to Brushed & Brushless Motors

Hey everyone. This is Eric Cooper. I’m here again with some food for thought in the tools industry. It has been several years now that brushless motors have begun to spread through the professional tools industry and change everything to cordless tools. What is really going on? You will face huge differences when dealing with brushed and brushless motors. But, before we go through these numerous differences, let’s take a look at the fundamentals of how a DC motor works. The first thing that comes to mind when operating a motor is all just the magnets. The oppositely charged magnets are completely attracted to each other. The basic observation inside a DC motor is to have a constant pull forward by keeping the opposite charge of the rotating piece (which is the rotor) and attracting the still magnets (which is the stator) in front of the rotor.

There are four main parts inside a brushed motor: a ring of magnets, an armature, carbon brushes and a commutator. The brushes and magnets are stable and not moving, but the armature and commutator rotate on the shaft together inside the magnets. When the motor is filled with electricity, there is a resulted charge that travels through the brushes and goes into the commutator. After that, the commutator transfers the charge to the armature (that they are made of copper windings). These windings are magnetized by the charge and pushed against the still ring of magnets that are around it and it forces the armature to rotate. This rotation of the armature doesn’t stop until the charge and electricity flow stops.

On the other hand, the brushes and the commutator are gone when you look inside a brushless motor. Also, the place of the windings and magnets are reversed. The magnets are placed on the motor shaft and the windings of the armature (which are made of copper) are fixed and around the shaft. The amazing part in the brushless motors is that a small circuit board (instead of the brushes and the commutator) controls the energy flow delivered to the windings. In conclusion, by equipping tools with this electronic communicator, you actually have a small computer inside your power tool.

Brushed vs. Brushless, the Pros & Cons

Because of their design and revolutionary technology, brushless motors bring more advantages over the brushed ones. The most belong to the efficient absence of the commutator and brushes. Because of the contact of brushes with the commutator to deliver a charge, a lot of friction is caused. This friction reduces speed and also brings heat to the motor. It is exactly like driving your car by slightly pushing the brake pedal. You will add the same effort as usual, but you will be slower. If you need the same speed, it will definitely take more energy from the engine. This is not what happens inside a brushless motor. Oppositely, brushless motors operate cooler and much more efficiently so that they will be able to deliver more power.

While you use your brushed power tool, the carbon brushes wear down. It is exactly what causes a spark inside some of the tools. If you want to keep your tool working, the brushes need to be replaced with the fresh ones once in a while. In contrast, the brushless tools (or it is better to say the brushless cordless tools) do not require this maintenance.

The rotor/stator combination in brushless motors is more compact with the help of the electronic controller. The resulted advantage is lighter weight and more compact size with more efficient performance. That is why we see so many power tools these days from the industrial manufacturers that have a superior compact design and more amount of power.

You might say that brushless motors are much more expensive to design and manufacture, but they are actually much more efficient than the brushed motors in power tools. The main positive points that come from them can be longer lifetime and less maintenance, more power, and longer runtime. Brands in the market often try to go for a balance between their tools’ power and durability in their performance. Some of them may go after producing a more powerful tool while some others might be interested in making power tools or cordless tools that are longer lasting. But the newly-technological brushless tools have become powerful enough so that all their manufacturers refer to their specifications as “corded-like performance”. Their value is twice when they are combined with the latest generation, high-capacity Lithium-ion batteries which are produced with the maximum capacity of 5.0Ah these days.

Why Spending Extra on the Brushless?

 The brushed DC motors are practically simple in design and the included parts are inexpensive, however copper is not becoming cheaper any longer. On the other hand, since brushless motors require that electronic communicator, you will basically have a small computer inside your cordless tool. And the result is a higher price for the brushless motors inside a more expensive tool than other “old-school” power and cordless tools.

Brushless for a Longer Lifetime

The combination of their advantages includes another main effect; longer life. While all the brushed and brushless tools are generally guaranteed to work for a considerable amount of time and under warranty by all the brands, you can be sure to get a longer life out of your brushless cordless models. It could even be years beyond the warranty.

Other Considerations

It isn’t true to say that brushless motors win over brushed motors for 100 percent all the time. For instance, moving the armature from the rotor to the stator will end to a reduction of mass distribution of the rotor. If I want to say it in a simpler way, the rotor in a brushless motor usually has lower amount of inertia than the same situation in a brushed motor. What does this mean? It means that a rotor in a brushed motor is more resistant to rotation. So, it is not just about increasing efficiency by decreasing the commutator frictional energy losses. Other advantages that need to be mentioned here are improved heat dissipation, flatter torque, more output power and reduced electrical noise.    

They are expensive and it is true. No doubt about it. They benefit the professionals better who are going to use them every day and can afford them. Brushless tools or better say, brushless cordless tools are somehow 30 percent more expensive to manufacture than other cordless tools, and their batteries are typically unavailable for most of the DIYers. But, by considering the advancement in the technology and design of batteries, you will be seeing more and more brushless tools at your local markets. They are designed and developed to stay, but it will take a while until all the power tools are equipped with this technology.