CS218827B1 - Method of heating commutators of electrical machines rotating under rotating magnetic field by electromagnetic induction - Google Patents

Abstract

The purpose of the invention is to improve the heating of commutators during rotation in a centrifuge while reducing the electrical power input. The stated purpose is achieved by connecting the lamellas at both ends of the commutator with conductive connections and allowing the commutator to rotate in a space with a counter-rotating magnetic field, preferably a multi-pole one. By intersecting the magnetic field with the lamellas at the sum of both speeds, an electromotive force is induced in the lamellas and thus an electric current flows, which heats the lamellas. At the same time, eddy currents are induced in the lamellas, which also heat the lamellas. Hysteresis losses arise in the magnetic parts of the commutator, which heat these parts. The invention is mainly used in low-speed commutators.

Description

The purpose of the invention is to improve the heating of the spinning commutators in a centrifuge while reducing the electrical input.

This is achieved in that in the commutator, the slats are connected at both ends by conductive connections and the commutator is rotated in a space with a counter-rotating magnetic field, preferably multi-pole. By intersecting the magnetic field with the lamellas the sum of both speeds induces an electromotive force in the lamellas and thus the flow of electric current occurs, which heats the lamellas. At the same time eddy currents are induced in the slats, which also heat the slats. In the magnetic parts of the commutator, hysteresis losses arise, which heat these parts.

The invention is mainly used in low-speed commutators.

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SUMMARY OF THE INVENTION The present invention provides a method for heating commutators of rotating electrical struts in a rotating magnetic field by electromagnetic induction.

According to the prior art, the commutator ^{1 is} preheated in a furnace to a prescribed temperature. It is then transferred to a centrifuge whose walls are heated by electrical resistance heating elements. In the closed space of the centrifuge, the air temperature is maintained at the temperature of the preheated commutator.

After centrifugation at the prescribed speed and prescribed time, the commutator has a temperature considerably lower than the pre-heating temperature. This means that the commutator is centrifuged at the prescribed temperature for only a certain time; much of it happens at a constantly decreasing temperature, so the spin effect is imperfect. The lamella bundle is not therefore; perfectly positioned so that in operation on the electric machine its additional deformations can occur resulting in its runout and the projection of individual slats. The result is brushing, commutator sunburn, and malfunction of the electrical machine. In addition, this prior art method of heating commutators during rotation requires considerable power input since the entire centrifuge must be permanently heated.

The temperature drop of the commutator during its centrifugation is caused mainly by the escape of heated air from the centrifuge space during the commutator insertion and also by the poor transfer of heat from the air to the rotating commutator.

These drawbacks are overcome by the heating method according to the invention, which is based on the fact that a commutator with conductively connected lamellae at both ends is allowed to rotate in a space with a counter-rotating magnetic field, preferably multi-pole, causing induction of electromotive force, and

Claims (1)

Method for heating commutators of electric machines rotating in rotation in a rotating magnetic field by means of electromagnetic induction, characterized in that the lamellas (2) of the commutator (1) are connected at both ends by conductive connections (3), (4) and commutator (1). It is allowed to rotate in the space with the counter 82 thus thereby the passage of electric current in the slats, as well as the induction of eddy currents in the slats and the occurrence of hysteresis losses in the magnetic parts, thereby heating the commutator. The generation of heat directly in the rotating commutator eliminates the heating of the entire centrifuge body, which does not cause any heat loss by opening it. The magnitude of the rotating magnetic field and the number of poles achieves the desired commutator temperature throughout its rotation. Once tested, the parameters will be permanently valid. Since the excitation of the rotating magnetic field is only performed during the commutator rotation, the power consumption is considerably reduced compared to the prior art method of heating the commutator during rotation. The accompanying drawing shows an exemplary embodiment of the heating of a commutator according to the invention. The lamellas 2 of the commutator 1 are simply connected at both ends by conductive connections 3, 4. The commutator 1 is then allowed to rotate in a space with a rotating magnetic field S counter-rotating. By intersecting the rotating magnetic field 3 with the slats 2 by the sum of both speeds, an electromotive force is induced in the slats 2, which causes the electric current to pass through the conductive connections 3, 4, which heats the slats 2. By intersecting the rotating magnetic field With the slats 2, eddy currents are induced in the slats 2, which also heat the slats 2. By rotating the magnetic parts, for example the steel part 6 in the rotating magnetic field 5, hysteresis losses occur in the steel part 6 by which the steel part B is heated. This method of heating commutators during rotation can be advantageously used in low-speed commutators. OF THE INVENTION with a directionally rotating magnetic field (5), wherein the commutator (1) is heated by inducing the electromotive force and passing the electric current through the slats (2) as well as by inducing eddy currents in the slats (2) and generating hysteresis losses.