If you're an RC car enthusiast, or have a passion for drone photography, you're probably more familiar with motor types and selection than most people. However, as as cordless power tool designs improve, more and more people are encountering different types of motors, and need to know about the options they have. Brushless motors are becoming more and more common, and are often touted as "better" than brushed motors, for good reason – in many ways, they are. But what does "better" really mean? In this article, we’ll briefly discuss some of the similarities and differences between brushed and brushless motors, and explain the advantages and disadvantages of each.
Fundamentally, a motor consists of two main parts: a rotor and a stator. The rotor rotates, and the stator is stationary. Simple, right? The trick is getting the rotor to rotate. The principles of electromagnetism tell us that when an electric current is passed through a wire, it generates a magnetic field. Everybody knows that magnetic fields of opposite polarity (north and south) attract one another, and those of identical polarity repel one another. So the secret to controlling the rotation of the rotor is controlling the electricity and the magnetic fields it generates inside the motor.
“Brushed” and “brushless” refer to how the electricity gets into the motor. There are many different subcategories of brushed and brushless motors, so we’ll discuss a general case here.
A brushed motor includes at least two carbon brushes, which are usually rectangular, spring-loaded chunks of graphite that are pressed against a part of the motor called the commutator. The electricity flows through the brushes and into the motor, causing it to rotate. As the motor spins, the brushes will eventually wear down and need to be replaced. In this type of motor, there are many different constructions, but one of the most common types used in cordless power tools is the PMDC (Permanent Magnet Direct Current) construction. In this type of motor, the stator is a set of permanent magnets, and the rotor is a set of stacked steel laminations, wound with wire. Brushed DC motors used in cordless power tools are often described using a standard frame number, such as 735.
A brushless motor, as the name suggests, does not have brushes, and may also be called a BLDC (BrushLess Direct Current) motor. Here, the rotor and stator never make physical contact. One of the most common constructions of brushless motors involves a permanent-magnet rotor, and a stacked-steel-laminate stator, which is wound with sets of wire. Brushless DC motors are described using their stator diameter and length in millimeters; for example, a motor with a 50mm diameter, 25mm long stator would be a 5025 motor.
Brushed motors are easier to control than brushless motors. Often, brushed motors used in cordless power tools are controlled by varying the voltage applied to the motor. The higher the voltage, the faster the motor spins. This ease of control makes them simple and inexpensive.
Brushless motors are more complicated, and require a set of programmed electronics to drive them, making them generally more expensive than brushed motors. In short, a brushless motor includes a sensor that sends feedback to a microcontroller, which decides when and where electricity is applied to the stator windings. The microcontroller sends power to the sets of stator windings in a rotating pattern, going around the stator. This creates a rotating magnetic field, with which the permanent magnets in the rotor attempt to align themselves. The microcontroller gets feedback about the motor’s position from the sensor, and makes any adjustments necessary. This continual adjustment keeps the motor spinning.
Brushed motors are the clear winners when it comes to cost and ease of use. They’re inexpensive, fairly durable, easy to find, and relatively easy to control. However, they’re noisier, less efficient, run hotter, generally larger, and need their brushes replaced eventually.
Brushless motors, on the other hand, are the obvious choice for power, ease of maintenance, efficiency, and longevity. As they proliferate, their costs are going down, making them more and more popular and more competitive with brushed motors. Even though they’re more difficult to control than brushed motors, they make up for that in being quiet, more efficient, virtually maintenance-free, more compact, and longer-lived.
It’s important to note that just because a tool uses a brushed motor, that doesn’t necessarily mean it’s a bad tool. Similarly, just because a tool uses a brushless motor, that doesn’t necessarily mean it’s a good tool. However, in a head to head comparison, brushless motors will win almost every time. They can pack more power into the same amount of space, or the same amount of power into less space, than a brushed motor; they last longer; they’re quieter; and they give better battery life.
WEN uses brushless motors in many of our cordless power tools for the reasons mentioned above. If you have any questions about the information in this article, or want to find out more about our 20V MAX or 40V MAX cordless power tool lines, please give us a call at 1-800-232-1195 (M – F, 8 – 5 CST), or drop us a message here to talk to our friendly and knowledgeable technical support team. Also, check out some of our other handy articles about cordless power tools.