For the purposes of this article, there are basically 2 kinds of electric motors, "brushed" and "brushless". Brushed motors have been around for about 150 years, but vast improvements in the early 1900 have left them almost unchanged since then, and for what they are, they are an excellent, efficient motors.
With the invention of the transistors in the 1960s, motor development took another step forward with the invention of the brushless motors. It is only because of higher technologies that these motors can work in a high enough efficiency to make the commercially viable because instant internal switching needs to occur.
Milwaukee of course have taken some of the early steps in this field by producing a series of brushless drills, Impact Wrenches and Hammer Drills.
In Brushed motors, there are something called brushes that make contact with a specific part of the armature of the motor, the part that spins. In a brushless motor there are no brushes, the spinning is done by using permanent magnets and and switching poles internally in the motor in order to make it spin. Here is a great video from Learn Engineering that explains in detail how this works and compares it with brushed motor ....
Like most things, brushless motors have their pros and cons. One of the most noteworthy cons is the fact that they are more costly to manufacture which sometimes can put them out of reach financially for the occasional power tool users. Another issue that can come up is they can be larger in size because the windings are on the outside of the armature. This isn't always the case because it can depend on designs, but all things being equal, a brushed motor would be slightly larger.
The advantages to brushless motors are simple, more work and more power from the same size tool. What that really means is that these new level of power tools are said to be "smart". What that means is that they can sense what they are drilling into and adjust the amount of power they need for the job. Unlike brushed motors that typically put all their energy into running the motor, regardless of what it is.
So what this means for the brushless motor is this. If, for example you re drilling through 1/8" plywood, the drill can sense this and applies only the power it needs to do the job. This means it draws less energy from the batteries thus, having the potential to have the batteries last longer between charges.
Brushless motors also tend to have more power than their brushed counter-parts and if you have ever used a brushed drill for a time you can actually feel the difference. One of the advantages I like the most is that brushless motors tend to last longer than brushed motors for a couple of good reasons.
1) there is no friction of brushes rubbing on the armature so this helps to reduce heat ... and obviously wear & tear on the tool.
2) Reduced heat. At least the potential for some reduced heat build up. Heat is one of the biggest enemies of motors because heat is what starts to break down the insulation over the wiring inside the motor. This breakdown of insulators often results in shorts inside the tool which is often why they quit working. In most case these breaks are not worth the time of effort to repair. Heat not only caused by brushes, so brushless motors are not immune to excessive heat buildup in extreme conditions.
Over time we will see more and more brushless motors added to various power tools. These will be tools that are the workhorses of the construction and redo industries. I do not expect to see wholesale changes in brushless technology added to more budget mined tools, only tools that are subjected to hard working conditions.
The nice thing with many tool manufactures is they give us choices. We can make the decisions on what tools suite us best depending on our use, our budget and what we are prepared to accept for future considerations. What is more important is that we have some knowledge of these things before we purchase and thus we can make informed decisions on what is best for our own situations and usage.
Copyright - Colin Knecht