Principle of Operation

Electric motors run by electromagnetism. However, there are also other types of motors that utilize electrostatic forces or piezoelectric effect. In the case of a PMDC (Permanent Magnet DC) motor, motion is produced by an electromagnet (armature) interacting with a fixed field magnet (housing assembly).

In a brushed motor, electrical current flows through the motor terminals in the endcap assembly that comes in contact with the commutator in the armature assembly through the carbon brushes or brush leaves. The electrical current powers the coils generating a magnetic field causing the armature to rotate as it interacts with the magnets encased in the housing assembly. Flemming’s Left Hand Rule helps to determine the direction of the force, the current and the magnetic flux.

In a brushless motor, when electricity is applied across the motor termination, a current flows through a fixed stator field and is interacting with a moving permanent magnet or a moving induced magnetic field inside a rotor / armature. After the motion and force load have been met by the available source current it returns back to the source exiting the motor.

Key Elements Interacting to Produce Motion

Magnetic Flux - A motor can have a fixed wound coil or a permanent magnet stator and a moving wound coil armature or PM rotor that will have interacting magnetic flux fields to produce a force and motion.

Force - The amount of current that flows through the electromagnetic field is proportional to the amount of interacting electromagnetic field force required to achieve the opposing work load. In addition to the force and motion needed by the device one must consider any efficiency loss in the conversion of electrical power into mechanical work (watts).