With regard to power tools. I’ve Googled and read, and it only seems to confuse me more. Thank you.
In: Engineering
There are two parts to an electric motor: the stator and the rotor. The stator is the stationary part and the rotor is the part that rotates. Both the stator and the rotor have magnets, and the magnetic attraction or repulsion is what causes the rotor to turn.
In most motors, the magnets are electromagnets, which are coils of wire that are hooked up to the power. The problem is, how do you connect up wires to the electromagnet on the rotor. It needs to turn, and if you just connect the wires directly they’ll twist around the shaft until they break. You need a way to get the power to the coil but not have a direct connection.
This is where brushes come in. Brushes are typically a small block of carbon that slide along, or “brush” along, a strip of copper attached to the rotor. The strip of copper is called the commutator. The commutator is connected to the coils on the rotor. With this arrangement you can supply electrical power to the rotor coil, and it is free to rotate without tangling the wires.
The problem with brushes is that they introduce a small amount of friction. They will wear out over time and need to be replaced. Also, if the rotor has multiple coils (which almost all brushed motors do), the commutator will be divided into segments with each segment connecting to a separate coil. In between the segments there are gaps. When the brush bridges the gap, there is a spark. This can be dangerous around flammable gasses and is electrically noisy as well.
However, there is no need for the magnets on the rotor to be electromagnets. We can create fairly powerful permanent magnets. By using permanent magnets on the rotor, we eliminate the need for brushes and commutators, and the whole rotor can be made smaller.
The key to a brushless motor is that there needs to be a rotating magnetic field in the stator coils. This is done with a clever little electronic circuit that energizes the stator coils in sequence. As the magnetic field in the stator coils changes, the permanent magnets turn the rotor to maximize the magnetic attraction and minimize the magnetic repulsion.
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