Electric motor

Electric motor switch, definition and function

Electric motor switch, definition and function

A commutator is a component used in electric motors and current generators. The switches have the function of a mechanical rectifier and a rotary switch in one. Reversing the direction of flow in the winding is called commutation.

The commutator of an electric motor is made of strips of hard electrolytic copper with insulating material in between. The assembly is insulated on the rotor shaft and the copper blades are connected to the anchor windings.

Permanently installed carbon brushes contact the commutator and provide power to the anchor windings.

What is the commutator of an electric motor?

A commutator is a rotary electrical switch in certain types of electric motors and electric generators that periodically changes the direction of the current between the rotor and the external circuit.

In an engine, it provides the power to the best location on the rotor, and in a generator, it receives the power in a similar way. As a switch, it has an exceptionally long service life, taking into account the number of opens and closes that occur in normal operation.

What is the commutator for in a motor?

The commutator is an important part in the operation of DC electric motors and generators. The switch performs the following functions:

  • Provide an electrical connection between the stationary carbon brushes and the rotating shaft with the rotor windings.

  • Act as a rotor angular position sensor.

  • Perform the function of current direction switch depending on the angular position of the rotor.

In the case of an alternator, the alternating current generated by rotating the rotor coils past the fixed-field magnets is converted into a direct current voltage. On the other hand, in the case of an electric motor it reverses the direction of the current in the rotor windings so that the armature continues to rotate.

How does a motor commutator work?

A commutator consists of a set of contact bars fixed to the rotating shaft of a machine, and connected to the armature windings. As the shaft rotates, the commutator reverses current flow in one winding.

For a single armature winding, when the shaft has completed half a turn, the winding is now connected so that current flows through it in the opposite direction to the initial one.

In a DC motor, the armature current causes the fixed magnetic field to exert a rotating force, or a torque, on the winding to make it rotate. In a generator, the mechanical torque applied to the shaft maintains the movement of the armature winding through the stationary magnetic field, inducing a current in the winding.

In the case of both the motor and the generator, the switch periodically reverses the direction of the current flow through the winding, so that the current flow in the circuit external to the machine continues in only one direction.

Publication Date: August 27, 2018
Last Revision: August 23, 2021