How do air core motors work?

Air core motors, also known as brushless DC motors (BLDC motors) when they are of the permanent magnet type, operate on the principle of electromagnetic induction. Here’s a simplified explanation of how air core motors work:

1. Construction: An air core motor consists of a rotor (the rotating part) and a stator (the stationary part). The rotor is typically a permanent magnet, while the stator is made up of a series of windings (coils) that form the motor’s phases. These windings are not surrounded by a magnetic material; hence, the term “air core.”

2. Electromagnetic Field: When an electric current flows through the windings of the stator, it creates a magnetic field around each coil. The strength and direction of this magnetic field can be changed by varying the current through the coils.

3. Torque Generation: The interaction between the magnetic field generated by the stator windings and the magnetic field of the permanent magnets on the rotor creates a force. According to the Lorentz force law, when a current-carrying conductor is placed in a magnetic field, it experiences a force. This force acts on the rotor, causing it to turn.

4. Commutation: In order to make the motor continue to rotate smoothly, the direction of the current in the stator windings must be changed as the rotor moves. This process is known as commutation. In brushless DC motors, this is typically done electronically using a controller that switches the current through the windings in a sequence that keeps the magnetic fields in the correct alignment to continue rotating the rotor.

5. Rotation: As the current in the stator windings is commutated, the magnetic fields produced by the windings continue to interact with the rotor’s magnetic fields, creating a continuous torque that causes the rotor to spin.

6. Speed Control: The speed of an air core motor can be controlled by adjusting the frequency of the current supplied to the stator windings or by varying the voltage. In a brushless DC motor, the electronic controller manages these adjustments.