What The Tech: The working prin­ciple of brushed motors and brush­less motors

There are two types of commonly used DC motors: Brushed motors, and brush­less motors (or BLDC motors). Learn about the working prin­ciple of Brushed motors and brush­less motors in this video.

Motors use a type of brush and, in some cases, they don’t. This means that the commu­ta­tion required for each elec­tric motor is mechan­ical. The sliding contacts transmit a constant voltage to the rotor. As it is made with an uneven number of wind­ings, the voltage constantly changes its polarity. Move­ment is gener­ated by the rotor in a perma­nent magnetic field, i.e. the stator. The brushes used must be replaced after approx­i­mately 10,000 oper­ating hours because they wear. This is no longer accept­able for fans that are oper­ated contin­u­ously these days.

This type of motor is simple and can be imple­mented rela­tively econom­i­cally. However, fric­tion on the brushes limits the effi­ciency and produces higher temper­a­tures. The carbon brushes wear out,
which neces­si­tates regular main­te­nance. Further­more, there is also regular elec­tro­mag­netic inter­fer­ence. With brush­less motors, coils instead of brushes ener­gize the rotor. Here, the rotor has the perma­nent magnets and the coils change their magnetic field through commu­ta­tion, meaning that the rotor is attracted or repelled. Because there is no contact between the stator and rotor,
there is no temper­a­ture increase during oper­a­tion and there is no wear.

In addi­tion to increased effi­ciency, this also means lower main­te­nance costs. In contrast to brushed motors, however, the manu­fac­turing process is more complex and some­what more expen­sive, but this pays for itself quickly thanks to long, main­te­nance-free oper­a­tion.

So, if the aim is for a partic­u­larly low-cost motor, a brushed motor is prefer­able. But if high effi­ciency and low main­te­nance are required, a brush­less motor should be chosen.