I. Definition of commutator
The commutator, also called the rectifier, is an important part of the armature of DC motors, DC generators and AC rectifier motors, which acts as a commutator when the motor is rotating, and is a component in order to be able to keep the motor rotating.
The commutator consists of a set of copper plates fixed around the circumferential part of the rotating machine or rotor and a set of spring-loaded brushes fixed to the fixed frame of the machine. Two or more fixed brushes are connected to an external circuit, which can be used either as a current source for the motor or as a load for the generator.
Second, the commutator working principle
The commutator consists of a set of contact strips fixed on the rotating shaft of the motor and connected to the armature winding. When the shaft rotates, the commutator reverses the current in the winding. In the case of a single armature winding, when the shaft has completed half a revolution, the winding is now connected so that the current flows through it in the direction opposite to the initial direction. In an electric motor, the armature current causes a rotational force or torque to be generated by a fixed magnetic field, which is applied to the windings to cause them to rotate. In a generator, the mechanical torque applied to the shaft maintains the motion of the armature windings through the fixed magnetic field, thus inducing a current in the windings. In the case of motors and generators, the commutator periodically reverses the direction of the current flowing through the windings so that the current in the circuit external to the motor continues to flow in only one direction. That is, when the coil through the current, will be under the action of permanent magnets, through the attraction and repulsion force rotation, when it turns to and magnet balance, the original energized wire more corresponding to the commutator on the contacts and brushes separated, and brushes connected to meet the group of coils corresponding to the contact of the coil to produce propulsion, so that non-stop repetition, the dc motor is turned up.
Third, commutator classification
1, from the open line way: a, groove type commutator; b, groove type commutator.
2, from the mechanical strength: a, ordinary type commutator; b reinforced type commutator.
3, from the bore structure: a, with bushing commutator; b, without bushing commutator.
4, from the copper row material: a, pure copper; b, cadmium cobalt copper; c, silver copper
Fourth, the role of the commutator
Commutator by a number of copper group (commutator) into a cylindrical or disk-shaped structure, between the copper by the mica or other insulating material insulation, each copper is connected with the armature winding elements, when the armature of the motor rotates when the copper successively with the fixed carbon brush contact. In a direct current generator, the alternating current in the armature windings is changed to direct current between the brushes by means of brushes and commutators. When the commutator connected to the ends of each armature winding element passes through the carbon brushes, the process of changing the direction or size of this current is called commutation. In the commutation process, if the carbon brushes and rectifier surface contact is poor, the carbon brushes and commutator contact surface may appear sparks, or even ring fire phenomenon caused by the winding burnout. In AC rectifier motor, the role of commutator is to make the frequency of alternating current between brushes meet the working requirements.
V. Application scope of commutator
Commutator is applied in the fields of power tools, household appliances, automobiles, motorcycle motors, etc. It is also applied in the fields of automobile generators and gasoline generators. They are mainly used in direct current (DC) machines, direct current (DC) generators and many DC motors as well as general-purpose motors. In an electric motor, the commutator applies current to the windings. By reversing the direction of the current in the rotating winding every half-turn, a steady rotational force (torque) is generated. In a generator, the commutator picks up the current generated in the windings and by reversing the direction of the current each half-turn, acts as a mechanical rectifier, converting the alternating current from the windings to unidirectional direct current in an external load circuit.
Commutators are relatively inefficient and also require periodic maintenance such as brush replacement. As a result, the use of commutator motors is declining, replaced by alternating current (AC) motors and, in recent years, brushless DC motors using semiconductor switches.
VI. Commutator Failure
1. Turn on the power, the indicator does not light up.
Method: Check the machine and replace the components.
2、Gas pressure cannot be adjusted in advance.
Method: check whether the wiring is correct and replace.
3、Main switch fuse broken wire.
Method: Check and replace.
