What is cogging effect

The cogging effect is the attraction between the magnets and the stator poles when at rest; this attraction and cogging is easily felt when trying to turn an electric motor by hand. A common misconception is that cogging is caused by the copper coils; however, this is not the case. An unequal attraction between the magnets and the stator results in the rotors reluctance to turn. The magnets sit comfortably at rest over a pole, and when the rotor is turned, they must move over an air gap before reaching the next pole. The rotor resists the turning, the magnets attempting to stay bonded to the current poles, until just over halfway through the air gap, where the attraction to the next pole is stronger than that of the previous pole, resulting in a "clunking" or jumping effect at low RPM (such as when trying to turn by hand). This is the cogging effect, resulting in a large torque required to begin rotation. The cogging effect is the attraction between the magnets and the stator poles when at rest; this attraction and cogging is easily felt when trying to turn an electric motor by hand. A common misconception is that cogging is caused by the copper coils; however, this is not the case. An unequal attraction between the magnets and the stator results in the rotors reluctance to turn. The magnets sit comfortably at rest over a pole, and when the rotor is turned, they must move over an air gap before reaching the next pole. The rotor resists the turning, the magnets attempting to stay bonded to the current poles, until just over halfway through the air gap, where the attraction to the next pole is stronger than that of the previous pole, resulting in a "clunking" or jumping effect at low RPM (such as when trying to turn by hand). This is the cogging effect, resulting in a large torque required to begin rotation.