Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K1/00—Details of the magnetic circuit
  • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
  • H02K1/22—Rotating parts of the magnetic circuit
  • H02K1/27—Rotor cores with permanent magnets
  • H02K1/2706—Inner rotors
  • H02K1/272—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis
  • H02K1/274—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis the rotor consisting of two or more circumferentially positioned magnets
  • H02K1/2753—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis the rotor consisting of two or more circumferentially positioned magnets the rotor consisting of magnets or groups of magnets arranged with alternating polarity
  • H02K1/276—Magnets embedded in the magnetic core, e.g. interior permanent magnets [IPM]
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K21/00—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets
  • H02K21/46—Motors having additional short-circuited winding for starting as an asynchronous motor

Definitions

• the present invention relates to a line start permanent magnet motor that operates asynchronously at the start-up and synchronously after start up.
• Hybrid type electric motors having asynchronous motor properties at the start, and synchronous motor features in continuous operation are utilized.
• Hybrid type electric motors are generally called "line start permanent magnet motor”.
• rotor of the hybrid type electric motor in addition to the structure of magnetic cage (squirrel cage) formed rotor bars having conductive and easily-shaped properties such as aluminum in the rotor slots and the end-rings that mechanically and electrically join these rotor bar ends on both surfaces of the rotor, permanent magnets are utilized that are emplaced inside the rotor.
• the hybrid motor starts asynchronously by means of the magnetic cage at the rotor and operates synchronously after start up by means of the permanent magnets placed in the rotor.
• the problem that arises in producing this type of rotors is reaching high temperatures while injecting aluminum material into the rotor slots and the magnets embedded in the rotor losing their magnetic properties due to high temperatures.
• the magnets can be placed in the rotor after the aluminum injection process however another problem, the displacement of the magnets placed later on, is encountered.
• the shape of particularly the end ring is changed depending on the arrangement of the magnets and the shape variations in the end rings results in magnetic flux irregularities and disruptions in the rotor balance.
• a permanent magnet synchronous motor which comprises a stator, a rotor and permanent magnets.
• the rotor comprises a rotor iron core, a plurality of conductor bars accommodated within corresponding slots in the rotor iron core and a starter squirrel cage conductor formed of a plurality of short-circuit rings positioned at axially opposite ends of the rotor iron core.
• the rotor includes magnet retaining slots on the inner sides of the conductor bars close to the periphery of the rotor and the permanent magnets are placed in these slots.
• End plates made of a non-magnetizable material is positioned between one or two laces of the rotor so as to prevent dislocation of magnets during operation. Shaping the short circuit rings depending on the magnet arrangement and making the cross-section thinner at some places results in the increase of electrical resistance and balance problems arise. Furthermore, a separate path opened in the rotor core is to inject the aluminum that acts as a rivet in order to fix the end plates.
• the aim of the present invention is the realization of a line start permanent magnet motor of which the start-up and operational efficiency is enhanced, comprising a low cost rotor with a simplified manufacturing process.
• a magnet retaining ring is used to prevent the scattering of the displaced magnets emplaced in the rotor core after the aluminum injection process during high speed operation.
• the magnet retaining ring is produced separately from the end ring of the rotor on the side of the emplaced magnets, and after the magnets are placed in the magnet inserting holes, is passed into the end ring and seated on the circular surface of the rotor core on the side wherein the magnets are disposed.
• the magnet retaining ring contacts peripherally the inner side of the end ring formerly shaped by aluminum injection and covers the magnet inserting holes partially or entirely.
• the end ring on the side of the emplaced magnets in the rotor and the magnet retaining ring form two rings, one inside the other, and the magnet retaining ring acts as the inner ring of the end ring and sharing the electrical load.
• the magnet retaining ring can be fixed inside the end ring by press fitting, screwing or supported by fixing pins, electrically conductive adhesive is applied on the contact surfaces of the end ring and the magnet retaining ring to provide fixing and electrical conductivity is enhanced.
• the fixing pin is inserted into the pin housings arranged oppositely on the outer side of the magnet retaining ring and the inner side of the second end ring. The fixing pin, when pressed or hammered into the pin housing, pushes the second end ring outwards in the radial direction and the magnet retaining ring inwards providing these elements to be contracted and the assembly to be reinforced.
• the magnet retaining ring can be produced in different sizes owing to the simple shape and can easily be adapted to different rotor and end ring designs.
• the magnet retaining ring prevents the displacement of magnets and the circular configuration thereof enhances the rotor balance.
• the magnet retaining ring, joining with the end ring, increases the total area for transmission of the generated flux, decreases electrical resistance and thus has a positive effect on performance.
• the electric motor of the present invention is used in implementations wherein startup moment and operational efficiency is important such as compressors of cooling devices.
• Figure 1 - is the schematic view of an electric motor.
• Figure 2 - is the perspective view of a rotor core.
• Figure 3 - is the perspective view of a state of the art rotor core and a squirrel cage structure formed of end rings and conductor bars.
• Figure 4 - is the perspective view of a rotor, the magnets to be disposed in the rotor and a magnet retaining ring.
• Figure 5 - is the perspective view of a rotor before the magnet retaining ring is mounted.
• Figure 6 - is the perspective view of a rotor after the magnet retaining ring is mounted.
• the line start permanent magnet motor (1) comprises a stator (2) and a rotor (3).
• the rotor (3) comprises a core (4) of cylindrical configuration formed of magnetic steel rotor laminations (L) slacked on top of each other with a shaft hole (D) at the center, one or more magnets (5) disposed by being embedded into the core (4) in the axial direction, providing synchronous operation, one or more magnet inserting holes (6) around the periphery of the shaft hole (D) wherein the magnets (5) are embedded, more than one rotor slots (7) inside the core (4) at a region near the outer periphery thereof, in the axial direction and in the same direction as the shaft hole (D) axis or extending along the core (4) in a sloped manner with respect to the shaft hole (D) axis, more than one conductor bars (8) formed by injecting aluminum into the rotor slots (7) in the injection mould (K), a first circular surface (9) situated at the aluminum injected side of the core (4), a first end ring (10) formed on the first circular surface (9) at the mould (K
• the core (4) is formed by stacking the rotor laminations (L) on top of each other, with the shaft hole (D), rotor slots (7) and magnet inserting holes (6) provided thereon and aluminum is injected from the first circular surface (9) by emplacing the core (4) in the aluminum injection mould (K). While aluminum is injected into the core (4) from the first circular surface (9), the penetration of aluminum material into the magnet inserting holes (6) and the shaft hole (D) is prevented by various methods.
• the magnets (5) are arranged in the magnet inserting holes (6) after the aluminum injection process and thus the magnets (5) are prevented from being affected by high temperatures.
• the rotor (3) of the present invention comprises a magnet retaining ring (12) produced separately from the second end ring (110), fitted on the second circular surface (11) of the core (4) by being inserted into the second end ring (110) after the magnets (5) are arranged in the magnet inserting holes (6), that contacts the inner side of the second end ring (110) peripherally and prevents the displacement of the magnets (5) by partially or entirely covering the magnet inserting holes (6) at the second circular surface (11) ( Figures 4, 5).
• the second end ring (110) does not have the dimensions to cover the magnet inserting holes (6).
• the magnet retaining ring (12) while preventing the displacement of the magnets (5) from the magnet inserting holes (6), and also being in full contact with the inner wall of the second end ring (110), shares the electrical load and decreases the resistance of the second end ring (110) which is made thinner for arrangement of magnets (5) after the injection by increasing the inner diameter thus increasing the electrical resistance. Furthermore, the circular shape of the second end ring (110) prevents the problem of balance during high speed operation.
• the core (4) is formed by stacking the rotor laminations (L) on top of each other, with the shaft hole (D), rotor slots (7) and magnet inserting holes (6) provided thereon and aluminum is injected from the first circular surface (9). Firstly, the first end ring (10) is formed on the first circular surface (9) with the injected aluminum, afterwards the aluminum is allowed to flow through the rotor slots (7) thus forming the conductor bars (8). The aluminum injected into the core (5) goes out from the rotor slots (7) on the rotor lamination (L) at the second circular surface (11), forming the second end ring (110).
• the magnets (5) are arranged in the magnet inserting holes (6). After the magnets (5) are arranged, the magnet inserting holes (6) are covered from above by the magnet retaining ring (12) that is mounted by being in full contact with the inner wall of the second end ring (110) and the displacement of the magnets (5) is prevented.
• the magnet retaining ring (12) is fitted inside the second end ring (110) by press-fitting.
• the rotor (3) comprises one or more fixing pins (13) that are disposed between the magnet retaining ring (12) and the second end ring (110) for fixing the magnet retaining ring (12) ( Figures 4,5,6).
• the rotor (3) comprises more than one pin housing (14), preferably shaped as half-cylindrical dents between which the fixing pin (13) is fitted, situated oppositely on the outer side of the magnet retaining ring (12) and the inner side of the second end ring (110) ( Figures 4, 5).
• the length of the pin housing (14) equals the thickness of the magnet retaining ring
• the fixing pin (13) presses on the magnet retaining ring (12) and the second end ring (110) by pushing inwards and outwards respectively and a configuration that deforms the structure of the rotor laminates (L) in the core (4) is not required for attaching the fixing pin (13).
• screw threads and grooves are provided on the outer side of the magnet retaining ring (12) and the inner side of the second end ring (110), and the magnet retaining ring (12) is fitted inside the second end ring (110) by screwing.
• an electrically conductive adhesive is applied on the outer side of the magnet retaining ring (12) and inner side of the second end ring (110), thus enhancing electrical conductivity therebetween as well as fixing the magnet retaining ring (12) to the second end ring (110).
• the magnet retaining ring (12) can be produced easily due to the simple ring structure thereof and be conveniently adapted to different rotor (3) and end ring (10, 110) designs.
• the magnet retaining ring (12) prevents the displacement of magnets and the circular configuration thereof enhances the rotor (3) balance.
• the magnet retaining ring (12), joining with the second end ring (110), increases the total area for transmission of the generated flux, decreases electrical resistance and thus has a positive effect on performance.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Permanent Field Magnets Of Synchronous Machinery (AREA)

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• 2007
  • 2007-07-20 WO PCT/EP2007/057506 patent/WO2008012269A1/en not_active Ceased
  • 2007-07-20 EP EP07787760A patent/EP2044672A1/de not_active Withdrawn

Non-Patent Citations (2)

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