Working principle of motor commutator

The working principle of the motor commutator is to periodically change the direction of the current in the coil to ensure that the direction of the electromagnetic torque is consistent, thereby maintaining the continuous rotation of the motor. ‌ ‌

1. Core principles and working process

Current direction switching mechanism

The commutator is composed of multiple copper commutator segments that work in conjunction with electric brushes. When the motor rotor rotates, the electric brush comes into contact with different commutator segments, automatically switching the direction of the coil current.

For example, when the coil rotates to the position of equilibrium with the magnetic field, the electric brush comes into contact with the commutation segment, and the current is temporarily interrupted; After relying on inertia to rotate to the equilibrium position, the electric brush is connected to the next set of commutator segments, and the direction of the current reverses, causing the direction of force on the coil to change, thereby driving the rotor to continue rotating.

2. Electromagnetic torque maintenance

If the direction of the current remains unchanged, the coil can only rotate half a turn in the magnetic field before stopping. The commutator periodically reverses the direction of current, causing the coil to always receive electromagnetic force in the same direction at different positions, forming a continuous torque.

3. Key structural role

Reversing plate (such as hook type, slot type): connects the armature winding and alternately contacts with the electric brush through rotation.

Electric brush: a fixed component that guides external direct current into the commutator and achieves current switching through sliding contact.

Technical characteristics and challenges

The commutator is prone to increased contact resistance due to electric sparks and wear during high-speed rotation, which may cause problems such as heating and insulation aging.

In modern technology, electronic commutators (such as BLDC motors) reduce mechanical wear and improve reliability and efficiency through brushless design.

application area 

Commutators are widely used in scenarios such as DC motors, power tools, and automotive motors, and are the core components for achieving the conversion of electrical and mechanical energy.