Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K17/00—Asynchronous induction motors; Asynchronous induction generators
  • H02K17/02—Asynchronous induction motors
  • H02K17/16—Asynchronous induction motors having rotors with internally short-circuited windings, e.g. cage rotors

Definitions

• the invention relates to an induction motor with short-circuited armature and a squirrel-cage formed of tubes - hereinafter pipe cage -, at which the bars of the cage are projecting beyond the frontal side of the rotor at one or both ends thereof and on the projecting ends there are short- circuiting means arranged, furthermore in the bar section between the short-circuiting means and the frontal side of the rotor, at least on one side of the rotor each single rod is provided with a tube made of a magnetizable material, being mutually electrically short-circuited.
• induction motors About 90 % of the electromotors operated all over the world are induction motors and about 4/5 of them are squirrel-cage motors. This can be explained by the fact that the slip-ring armature motors - although their operational properties are far more advantageous - are often causing break-down due to the slip-ring and the brushes, which easily get damaged; besides said motors are rather expensive, involving more costs than the induction motors with short-circuited armature.
• the drawback of the induction motors with short-circuited armatures lies in that they are starting with a considerably higher current absorption, simultaneously the starting torque is less, they endure less startings, regulating of the number of revolutions involves high costs.
• the HU-PS 154089 and the corresponding GB-PS 1,121,239, respectively, describe a solution, at which in case of an induction with short-circuted armature, where the bars of the cage - the rotor bars - are protruding beyond the frontal side of the rotor at one or both ends thereof and on the ends of the single protruding bars there are shortcircuiting means arranged, in the bar section between the short-circuiting means and the frontal side of the rotor, at least on one end of the rotor there is a tubular, magnetizable, mutually electrically short-circuited material arranged.
• the aim of the invention has been to eliminate the difficulties mentioned above and to improve the induction motor with a short-circuited armature and a pipe cage, as previously described, at which partly the detrimental lengthening of the motors, partly the reduced efficiency caused by the overlong bars can be avoided.
• the invention aims to provide a solution, by means of which at induction motors with a short-circuited armature and a pipe cage, at which the cage-tars are protruding beyond the frontal side of the rotor at one or both ends thereof and on said protruding ends of the bars short-circuiting means are arranged, furthermore in tho bar-section between the short-circuiting means and the frontal side of the rotor, at least on one side of the rotor each rotor bar is provided with magnetizable tubular materials in a mutual electrical short-circuit connection, the difficulties and drawbacks previously described can be eliminated.
• the task set is solved in such a manner that by the proper selection of the wallthickness, under the influence of the starting current of the rotor partly the tubes are reaching or at least well approximating the state of magnetic saturation, partly the Skin-effect is arising in them. It was found that after having exceeded the limit value of the magnetic saturation,the power factor becomes worse, an the other hand, when saturation does not come up to said limit value, actually superfluous masses will be present and unmotivatedly large space requirements have to be reckoned with.
• the increased resistance caused by the Skin-effect - which again results from the increased wall-thickness - has been utilized. Due to the Skin-effect, in dependence of the root of frequency instead of the total cross-section of the tube, the current engages but a part of the wall-thickness - e.g. at a period of 50 -, amounting to 1 - 1,5 mm,accordingly, in case of a wall-thickness of 6 mm a fourfold increase in resistance may be obtained, i.e. a quarter of the tube length proved to be sufficient.
• the rotor, bars are to be lengthened only by the length-plus resulting from the coil heads arranged on both sides of the rotor of the slip-ring armature motor, i.e. the length of the case of the slip-ring armature motor has not to be increased, nevertheless, an equal, but even a batter efficiency can be achieved than at the slip-ring armature motors, since the tubes flattened to the form of a notch, lying on the rotor, but outside and having been separated from the same, are exhausting the majority of the heat of the rotor, thus reducing inner losses.
• a further advantage may be obtained by providing the tubes with one or more slits forming air gaps in longitudinal direction, preferably along the external and/or internal generatrix, which is lengthening the beginning horizontal starting section of the magnetizing curves.
• the tubes are made of cast magnetizable material.
• the tubes are formed with a cross-section having been flattened e.g. to the shape of a notch.
• the tubes are provided with one or more slits forming air-gaps in longitudinal direction, preferably along the external and/or internal generatrix.
• the tubes and air-gaps made of magnetizable material can be formed in two or more sections of appropriate arc shape.
• a further embodiment of the invention may be developed such that the tubes are attached to two tube supporting discs, one of which being arranged in such a manner that it could slide longitudinally along the shaft of the motor.
• the securing rings if required are attached to the outer part of the tubes.
• fan-blades are arranged on the tubes or on a part thereof.
• jalousie-like blow-off openings can be formed in the wall of the motor casing.
• the rotor bars are lengthened for the purpose of pulling the pipe-cage onto the bars.
• said lengthening of the rotor bars cannot be greater than the cut stretch of the coil heads of the rotor of a slip-ring armature motor.
• the pipe-cage i.e. the squirrelcage formed of tubes, however, causes unnecessary plusresistance. For eliminating this, the insulation of the rotor bars is removed from their outermost surface in the area of the tubes near to the coil head.
• the short-circuiting action can be effected fully sparkless and contact surfaces can be maintained constant by making the end parts of the tubes being next to the coil head anti-rust and anti-corrosive, e.g. by electroplating.
• the tubes may be arranged outside the coil heads, accordingly, their heating-up at the start does not influence the inner coiled part of the motor, as a consequence closed arrangement becomes possible;
• the tubes placed onto the rotor bars do not exert a transforming influence as a consequence, the original low rotor resistance will be restored, the tubes are cold, simultaneously the lengthening of the rotor bars quasi "exhaust" the heat from the rotor. Accordingly, the stator will be also colder by about 20 %, enduring better the overload;
• Fig. 1 is a schematically illustrated longitudinal section of the embodiment according to the invention
• Fig. 2 is showing the siitted tube in a part-sectional longitudinal view
• Fig. 3 is a cross-section of the tube according to Fig.2;
• Fig. 4 is representing the load-torque curve of the motor according to the invention in dependence of the speed of rotation
• Fig. 5 is showing the power consumption of. the tubes of the motor in dependence of the current of the rotor bars.
• the rotor bars 1 are axially lengthened and thus protruding from the iron body of the rotor.
• the tubes 2 are arranged; the tubes are made of a magnetizable material, e.g. cast steel, between the rotor bars 1 and the cubes 2 the insulation 3 can be found advantageously made of raicafoil.
• the insulation 3 of the rotor bars 1 is removed from their outermost surface in the area la of the tubes 2 near to the coil head.
• the end parts of the tubes 2 being next to the coil head are made anti-rust and anti-corrosive, e.g.. by electroplating.
• Each of the tubes 2 have been fixed in two tube supporting discs 4. Said supporting discs 4 simultaneously fulfil the task of short-circuiting the bars 1, accordingly, the tubes 2 should be attached bv welding, Taking into consideration that at the tubes 2 - due to changes in temperature - longitudinal deformation may also accur, in order to compensate the changes in dimension, the tube supporting discs 4 to be seen on the left side are arranged in a slideable manner, displaceable longitudinally along the shaft 13 of the motor.
• the securing rings 9, 10 serve for stabilizing the position of the tubes 2, as v/ell as for compensating the centrifugal force arising in course of rotation; said rings 9, 10 are expediently welded to the tubes 2.
• the rotor - has been arranged by means of the internal, e.g. by the rightsided supporting disc 4, the sealing 6 or by meany of a separate cover plate in a closed manner, ensuring the closedness in accordance with the prescriptions of the standard IP 44.
• a closed motor may be obtained, from which the heat is led away by means of the rotor bars 1, as a consequence, a considerable improvement can be achieved in relation to the efficiency of the motor, also resulting in a decrease in temperature by about 20 Co at the stator, i.e. using the same copper quantity a higher efficiency may be achieved.
• Fig. 1 the directions of the air current are indicated by arrows.
• Fig. 2 and 3 the longitudinal and cross_sections of the tube 2 have been illustrated.
• the cross-section of the tube 2 has a shape identical with the notch; for the sake of a better cooling and in order to be able to place more tubes, the cross-section of the tube 2 is shaped in a flat and oval form.
• the size of the slitted air-gap 12 used to amount to 0,5 - 1,5 mm The task of said air-gap 12 is to inhibit the occurance of the transformation affect, in course of normal oporation of the motor, accordingly transformation cannot take place. As a consequence, at a certain overload of the motor reduction of the speed of rotation does not take immediately place, i.e. the motor becomes less sensitive to overload.
• By increasing the size of the air-gap insensitiveness will also increase, but after having exceeded a certain limit value, cos ⁇ becomes worse. According to our observations this limit value lies well over 1 mm.
• the curve “a” belongs to the slip-ring armature motor, without rheostat, the curve “b” to the motor with double squirrel-cage, while the curve “c” belongs to the motor with pipe cage formed in accordance with the invention.
• Fig. 5 the development of the power consumption of the pipe cage has been illustrated in dependence of the current of the rotor bars, particularly, when using tubes within wall-thickness of 5, 6 and 7 ram respectively.
• the curve drawn in a dashed line is showing the modification of the curves caused by slitting the tubes 2.
• the tubes are smoothing, as a consequence, compared to sinusoidal control, reduction at the torque cannot be observed;
• the induction motor with the short-circuit armature and pipe-cage formed according to the invention does not "stall", it only decelerates;
• the tubes perform self-ventilation in a considerable extent, they are insensitive and endure a degree of temperature of several hundred centigrades.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Induction Machinery (AREA)
• Motor Or Generator Cooling System (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

Family

ID=10948494

Family Applications (1)

Country Status (11)

Cited By (1)

Citations (4)

Family Cites Families (7)

• 1980
  • 1980-01-31 HU HU8080210A patent/HU181044B/hu not_active IP Right Cessation
• 1981
  • 1981-01-27 JP JP56500547A patent/JPS57500135A/ja active Pending
  • 1981-01-27 AU AU67706/81A patent/AU6770681A/en not_active Abandoned
  • 1981-01-27 WO PCT/HU1981/000007 patent/WO1981002228A1/en active IP Right Grant
  • 1981-01-27 BR BR8106183A patent/BR8106183A/pt unknown
  • 1981-01-27 EP EP19810900341 patent/EP0044328A4/en not_active Withdrawn
  • 1981-01-28 ES ES499478A patent/ES8202202A1/es not_active Expired
  • 1981-01-29 IN IN98/CAL/81A patent/IN152660B/en unknown
  • 1981-01-30 IT IT8119440A patent/IT8119440A0/it unknown
  • 1981-09-14 FI FI812860A patent/FI66710C/fi not_active IP Right Cessation
  • 1981-09-29 DK DK430981A patent/DK430981A/da not_active Application Discontinuation

Patent Citations (4)

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