In this article we show how a brushed motor is made and works.
The structure of a brushed motor
A brushed motor consists of a fixed part and a rotating part, called stator and rotor, respectively.
The elements of the fixed part (stator) are the case, bearings, magnets and brushes connected to the power cables. The rotating part (rotor), on the other hand, consists of the shaft, armature, turns and commutator.
How the brushed motor works
The wire is wound around the armature in a number of turns, and each group of turns constitutes a coil. The number of turns is the same for each coil and is a predetermined number depending on the characteristics the motor must have.
🔧 The lower the number of turns, the greater the motor's power, maximum rpm and its maximum torque.
The number of coils depends on the geometry of the armature: normally there are 3 and they are arranged at 120° from each other, but in recent brushed motors the coils can be as many as 5. This type of motor is the most commonly used especially in scaler/crawler categories.
The commutator is divided into as many sectors (slots) as there are coils, and one turn per coil is connected to a slot. When the brushes touch the commutator, two slots at a time are energized and current circulates in the turns and, therefore, in the coils.
🔧In order to understand why the motor turns, it is essential to know that each coil traversed by current constitutes an electromagnet.
During rotation, the contact of the brushes continuously moves from one slot of the commutator to the next; each time this transition occurs, the magnetic polarity within the coil (electromagnet) is reversed, creating a periodic alternation of attraction/repulsion between the electromagnets and the case magnets.
We have chosen an animation from the web to best clarify our entire discussion, in which each element involved in operation can be well distinguished.
You can see the precise moment when switching occurs in the 3 coils, which change their polarity and react with the permanent magnets N and S in the case.
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