Electric motors. The degree of health of the collector motor. Scheme, description

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Electric motors. The degree of health of the collector motor. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Electric motors

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Anyone who, by the nature of his activity or by virtue of natural curiosity, has dealt with DC motors, certainly had to pay attention to the constant sparking present on the engine manifold during its operation. In itself, sparking does not necessarily indicate a malfunction of the engine or the impossibility of its operation, since the causes of sparking are very different: from the presence of blackening on the commutator or soot on the brushes to their incorrect installation and poor fit of the brushes to the commutator or increased vibration of the brush device.

Practice shows that it is not possible to completely get rid of sparks on the collector even if the motor brushes are installed absolutely correctly, according to factory standards, with a snug fit to the collector; if there is no vibration, if the surface of the commutator and brushes is free of dirt, blackening and deposits.

The task of a home electrician working with a DC motor is to learn how to correctly determine the degree of permissible sparking on the collector. And for this, there are certain standards of sparking, knowing which you can easily distinguish a serviceable engine (despite the presence of sparking) from one that needs preventive maintenance in a repair shop.

The norms are determined according to a specially developed class scale, the so-called switching classes (Table 9).

Table 9. Degree and characteristics of arcing on the collector of a DC motor

Electric motors. Degree of serviceability of the collector electric motor

Operation of motors of 1, 1,25 and 1,5 commutation classes is possible without restrictions. Motors with sparking of the 2nd class of switching can only be operated if it occurs only at times of a sharp increase in load or when operating in overload mode.

The third switching class limits the possibility of further operation of the motor. If both the collector and the brushes are in a condition suitable for work, then such sparking is permissible only at the moment of direct switching without using rheostatic steps or reversing the machine.

An experienced electrician can determine the degree of possibility of further operation of the electric motor, not only by the characteristic of sparking and the condition of the collector and brushes, but also by the color of the sparks appearing on the collector:

- small bluish-white sparks, almost always present on the running edge of the brush, allow further operation of the engine without any restrictions; such sparks are typical for 1, 1,25 and 1,5 switching classes;

- the appearance of elongated sparks of a yellowish tint indicates that the spark belongs to the 2nd class of switching; further operation of the engine is possible with minor reservations;

- if the sparks have acquired a green color, and there are particles of copper on the working surface of the brushes, then the electric motor can no longer be operated, since there is mechanical damage to the motor collector. The only repair operation that a home electrician who does not have special knowledge of electrical engineering can undertake is the replacement of worn brushes. To do this, it is necessary to remove the cover of the motor housing and the caps of the brush holders, disconnect the worn brushes and install new ones, observing the type of connection with the contacts (twisting or soldering).

Other repairs of electric motors are strongly recommended to be entrusted to professional specialists, since both AC and DC motors are mechanisms that are quite complex and expensive to carry out experiments and experiments on them.

Author: Korshevr N.G.

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