A commutator is a specialized slip ring that is commonly used on direct current motors and electrical generators to transmit electrical power between the stationary housing and the revolving armature while also reversing the direction of the electrical current. A special type of commutator, the slip ring, consists only of this circular metal plate with holes in it. It's used instead of a brush on a motor or generator because it doesn't wear out as quickly.
Commutators are used where mechanical contactors (such as brushes) would be inconvenient or impractical, such as for supplying power to moving parts of an aircraft engine or another device where there is a need to avoid any possibility of sparking. They also find application in large machinery where regular maintenance of spark-producing components such as brushes is difficult or impossible.
The commutator mechanism itself consists of two parts: a center ring and a set of outer rings. The number of pins on the center ring corresponds to the number of wires going into the motor case. These pins connect to the ends of the coils in the rotor. As the rotor turns, these pins move past corresponding sockets in the stator, which are connected to the opposite end of each coil. Thus, electricity can flow through the wire connecting the pin on the center ring to one socket in the stator, along the corresponding coil, and through the other socket to the next pin on the center ring.
In some types of electric motors and generators, a commutator is a rotating electrical switch that periodically flips the current direction between the rotor and the external circuit. By reversing the current direction in the spinning windings every half turn, a constant rotating force (torque) is created. This allows the motor to continue running even when power is not being applied to it directly.
Commutation occurs when you switch the voltage on a DC motor's winding coil from one end to the other. If you don't switch the polarity of the voltage quickly enough, the magnetic field generated by the current in the winding will keep the magnet in place, and more than one coil will be energized at a time. This condition is called "polyphase power" and is not suitable for most small motors because they can't generate enough torque to overcome the load driving them. Instead, use a single-phased power supply or inverter.
For efficient operation, all electric motors should be driven by sinusoidal voltages. This means that the voltage across any two points on the motor's armature must be equal, but opposite in phase.
The commutator, also known as a slip ring, changes the direction of current via the coil every half cycle. This allows the rotor to continue spinning even when the electrical power is off, so it can be kept running by an auxiliary source such as a battery.
The commutator consists of a set of copper segments that are attached to the outer circumference of the rotor shaft. These segments are housed within a metal casing which is connected to the stationary part of the electric machine. When current is passed through the coils of the electric motor, the magnetic field produced by the currents will cause the rotor to spin. As the rotor spins, the commutator segments will come into contact with the casing and change direction of the flow of current.
When the electric motor is shut down, the rotor will stop rotating immediately because there is no longer any way for it to turn. The stator will still have a magnetic field, however, so all the iron components inside the motor (including the rotor) will keep the magnetic field intact. This means that when the power is next turned on, the motor will start right back up again without delay or problem.
The commutator allows the motor to run continuously even when the electricity is off, but it also has some serious drawbacks.
In a dc generator, however, the slip rings are replaced by two split rings that execute the commutation process. Commutation is the process of converting alternating current (AC) electricity to direct current (DC). The commutator is a collection of revolving split rings and the carbon brushes to which they are linked. As the rings rotate, they come into contact with the brushes, which completes the circuit for each brush. When one brush breaks down or fails completely, it can be replaced without removing the battery. The commutated current from all the other brushes provides all the power for normal operation of the generator.
Split rings are used instead of slip rings because they do not require any lubrication and therefore can function in a dusty environment. They also have lower resistance than slip rings; this means less loss of voltage during transmission and more constant generation of power.
Furthermore, split rings do not interfere with the magnetic field produced by the rotor, so they can still operate properly even when parts are missing from the rotor.
These rings must be made from material with low resistance to current, so they will not heat up and cause damage to the generator. They may also need to be insulated from each other, depending on the application. If there is no insulation between them, they could short out and cause problems further down the line.
The commutator assembly includes a center ring and two end rings that fit inside it.
The Standard Electrical Dictionary Please rate this definition: Split Ring, Commutator A two-division commutator for a motor made of two segments of brass or copper plate twisted into arcs of a circle and joined to an insulating cylinder. The outer segment is connected to the armature winding while the inner segment carries no current but passes all power to the outer one when it is turned by the motor shaft. This prevents short circuits between the phases of the wire inside the rotor. Split rings are used in place of brushes in direct-current motors.