Frequently asked questions and answers

Here you can find questions frequently put to us and their answers.

What is a commutator?

The commutator is an important component in the construction of DC motors. Its task is to supply the rotating armature (rotor) with current in such a way that the it flows through the individual windings at the right moment and in the direction of the current, so that, according to the Lenz’s Law of Induction, the rotor moves in the intended direction.

In terms of construction, this involves a rotationally symmetrical body comprising of electrically conductive single segments (copper) according to the number of windings of the rotor. These are, in turn, electrically isolated from each other by means of mica sheets. The individual parts are joined with a duroplast moulded compound in the transfer moulding process.

The commutator is mounted immediately adjacent to the winding on the rotor shaft and the ends of the windings are each interconnected with two staggered commutator segments (winding step). The transfer of the current to the rotating commutator is executed via carbon brushes.

In terms of construction, the design and manufacturing quality of the commutator must ensure that it is able, as a composite body, to withstand the high centrifugal forces during the rotation and transfer the required strength of current below the given armature voltage without having this leading to unwanted short circuits.

Direction of use of commutator？

The commutator is mainly available in hook type, groove type, flat type and the like. Made of imported raw materials, the performance of the products has reached the international advanced level, and is widely used in electric tools, household appliances, automobiles, motorcycle motors, etc.; collector rings, carbon brush holders, wiring boards have various specifications and models, applications In the field of automotive generators, gasoline generators and so on. The commutator acts as a rectifying function, which acts to make the direction of the current in the armature winding alternating so as to ensure that the direction of the electromagnetic torque is always constant. In a generator, the commutator can cause the alternating potential in the component to become a direct current potential between the brushes; in the motor, it can cause the applied direct current to become an alternating current in the component, producing a constant direction of torque.

The commutator and the brush form a corresponding sliding friction pair in the motor. The influence of the commutator on the performance of the motor mainly depends on the electrical contact behavior when the brush is slid at a high speed under certain conditions. In addition to the transmission of the longitudinal current, the commutator also has a current commutation task in the short-circuit armature coil.

Commutator measurement method and judgment？

For the problem of the commutator brush spark still can not be solved by the conventional method, when the machine is stopped, the DC resistance value between the adjacent two pieces of the commutator rotor commutator is measured by the QJ44 type double-arm bridge. Shown. It should be noted that it is absolutely not allowed to use the wire to connect the C and P terminals to the two test cables at the double-arm bridge. Otherwise, the influence of the contact resistance between the test leads and the commutator segments on the measurement results cannot be eliminated.

Before the measurement, the surface of the commutator is polished with water sandpaper, the residual toner between the sheets is removed, and the commutator rotor is blown off with compressed air. The commutator segments are numbered sequentially with a marker.

The commutator is a high-speed rotating device whose rotor winding is subjected to electrodynamic force and centrifugal force. Although it has been operated under rated parameters for a long time, the commutator of the rotor winding and the commutator riser is a commutator. The weak link of the rotor, and the traditional soldering process, combined with the measurement results of the DC resistance between the sheets, judges that the solder joint between the rotor winding and the commutator riser is loose, causing the end wire to fatigue and increase the contact resistance. The heat generation increases, the oxidation of the contact surface is accelerated, the contact resistance is further increased, and the heat generation is further increased. Such a vicious cycle eventually causes the commutator rotor insulation to burn at a high temperature, discharges the ground arc, and destroys the commutator. . The results of the commutator disintegration test show that the test data and judgment conclusions of the rotor winding are accurate.

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