Description AN ELECTRIC MOTOR

[0001] The present invention relates to a line start permanent magnet motor that operates asynchronously at the start-up and synchronously after start up.

[0002] Particularly in implementations wherein high start up moment and high operational efficiency is important, for example in compressors of cooling devices, 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". In the rotor of the hybrid type electric motor, in addition to the magnetic cage (squirrel cage) structure formed with 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. In order to solve this problem, the magnets can be placed in the rotor after the aluminum injection process however, in order to place the magnets, particularly the shape of the end ring is changed depending on the layout arrangement of the magnets and the shape variations in the end rings result in magnetic flux irregularities and disruptions in the rotor balance.

[0003] In the European patent application no. EP1519471, a permanent magnet synchronous motor is described 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. Furthermore, 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 inserted in these magnet retaining slots. End plates made of a non-magnetizable material is positioned between one or two feces of the rotor so as to prevent dislocation of magnets during operation. Shaping the short circuit rings depending on the magnet layout arrangement and making the cross-section thinner at some places result in the

increase of electrical resistance and balance problems arise. Furthermore, a separate path has to be opened in the rotor core to inject the aluminum that acts as a rivet in order to fix the end plates in the production of this type of rotor.

[0004] In the United States of America patent application no. US2004256939, the rotor of a line start permanent magnet motor and a manufacturing method thereof is described. A supporting plate is not used at the side wherein magnets are inserted for preventing displacement of magnets embedded into the rotor core during operation but instead the end ring is formed so as to cover the magnet slots and the end ring is provided with magnet paths thereon sized for passing through the permanent magnets. After the injection process of end rings and the conductor bars on the rotor core is completed, the magnets are passed through the magnet paths to be embedded in the rotor core and afterwards the fixing members are mounted on the magnet paths for preventing the magnets from being separated. The magnet paths make the production of end rings more difficult, provide a barrier for the magnetic flux and increase electrical resistance.

[0005] 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.

[0006] The electric motor realized in order to attain the aim of the present invention is explicated in the attached claims.

[0007] In the electric motor of the present invention, stoppers are provided on the last rotor lamination on the side of the second surface depending on the direction of injecting aluminum into the rotor core, formed by cutting the steel sheet used in producing the rotor lamination, allowing the securing of magnets by opening the top of the magnet inserting holes when folded outwards from the rotor lamination, covering over the magnet inserting holes when folded towards the rotor lamination and preventing the displacement of the magnets.

[0008] The stoppers are produced in the shearing mould in a form not folded outwards from the rotor lamination and afterwards are folded outwards from the rotor lamination with a separate bending mould or by manual operation.

[0009] The stoppers cover an area at the center of the narrow rectangular shaped magnet inserting holes, smaller than the magnet inserting hole, and can easily be folded to be opened or closed particularly by simple hand tools.

[0010] The extensions of the stoppers are formed in the shearing mould wherein the rotor laminations are produced, by opening thin U shaped slits that intersect in the lengthwise direction the area wherein the magnet inserting holes are situated.

[0011] In another production method, the stoppers can be manufactured in folded form in the shearing mould wherein rotor laminations are produced and the rotor lamination that comes out of the shearing mould are directly grouped together with the other rotor laminations to form the rotor core.

[0012] The stoppers prevent the displacement of the magnets arranged in the magnet inserting holes in the core after the aluminum injection process, the use of an additional element is not required to prevent displacement of the magnets and the balance problem that can be caused by additional elements is avoided.

[0013] 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.

[0014] The electric motor realized in order to attain the aim of the present invention is illustrated in the attached figures, where:

[0015] Figure 1 - is the schematic view of an electric motor.

[0016] Figure 2 - is the exploded perspective view of a rotor core, end rings, conductor bars and the magnets.

[0017] Figure 3 - is the perspective view of a rotor lamination with stoppers disposed thereon.

[0018] Figure 4 - is the perspective view of a rotor lamination with the magnets arranged and the stoppers in the open position.

[0019] Figure 5 - is the perspective view of a rotor lamination with the magnets arranged and the stoppers in the closed position.

[0020] The elements illustrated in the figures are numbered as follows:

1. Electric motor

2. Stator

3. Rotor

4. Core

5. Magnet

6. Magnet inserting hole

7. Rotor slot

8. Conductor bar

9. First surface

10. , 110. End ring

11. Second surface

12. Stopper

[0021] The line start permanent magnet motor (1) comprises a siator (2) and a rotor (3).

[0022] The rotor (3) comprises a core (4) of cylindrical configuration with a shaft hole (D) at the center formed of magnetic steel rotor laminations (L) stacked on top of each other, one or more magnets (5) disposed by being inserted into the core (4) in the axial direction, providing synchronous operation, one or more magnet inserting holes (6) disposed around the shaft hole (D) wherein the magnets (5) are inserted, more than one rotor slot (7) disposed at a region near the outer side of the core (4), extending in the axial direction such that the skew angle is zero or different from zero, in the same direction as the shaft hole (D) axis of the core (4) or in a sloped direction with respect to the shaft hole (D) axis, more than one conductor bar (8) formed by injecting aluminum into the rotor slots (7) in the injection mould (Kl), a first surface (9) situated at the aluminum injected side of the core (4), a first end ring (10) providing the connection of the conductor bar (8) ends to each other at the first surface (9), a second surface (11) situated at the side wherein the injected aluminum goes out of the core (4) and a second end ring (110) disposed on the second surface (11), providing the connection of the conductor bar (8) ends.

[0023] During the production of the rotor (3) the core (4) is formed by stacking the rotor laminations (L) on top of each other after being shaped in a shearing mould (K2), with the shaft hole (D), rotor slots (7) and magnet inserting holes (6) provided thereon and aluminum is injected from the first surface (9) by emplacing the core (4) in the aluminum injection mould (Kl). While aluminum is injected into the core (4) from the first 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.

[0024] The rotor (3) of the present invention comprises one or more stoppers (12) formed as part of the last rotor lamination (L) that are provided over the magnet inserting holes (6) on the last rotor lamination (L) on the second surface (11) side of the core (4), by cutting the steel sheet material used in producing the rotor lamination (L), allowing the insertion of magnets (5) by opening the top of the magnet inserting holes (6) when folded outwards from the rotor lamination (L) plane, covering over the magnet inserting holes (6) when folded towards the rotor lamination (L) plane after the magnet (5) is placed in the magnet inserting hole (6) thus preventing the displacement of the magnet (5).

[0025] The stopper (12) covers an area at the center of the magnet inserting hole (6) shaped

as a narrow rectangle, that is smaller than the magnet inserting hole (6). The stopper (12) is not required to cover the entire magnet inserting hole (6) in order to prevent displacement of the magnet (5), covering only a small area at the center of the magnet inserting hole (6) is sufficient. Since the area of the stopper (12) is small, it can easily be folded to be opened or closed particularly by manual operation.

[0026] The extensions of the stoppers (12) are formed in the shearing mould (K2) wherein rotor laminations (L) are produced, by opening a thin U shaped slit that intersects the area wherein the magnet inserting holes (6) are situated in the lengthwise direction. The area surrounded by the U shaped slit opened in the rotor lamination (L) forms the stopper (12). When the rotor laminations (L) are grouped, a single rotor lamination (L) with stoppers (12) arranged thereon is disposed on the second surface (11) side of the core (4).

[0027] The stoppers (12) are produced in the shearing mould (K2) in a form not folded outwards from the rotor lamination (L) and afterwards the stoppers (12) are folded outwards from the rotor lamination (L) by means of a separate bending mould or by manual operation.

[0028] In another production method, the stoppers (12) can be manufactured in the shearing mould (K2) as folded outwards from the rotor laminations (L). In this embodiment, the rotor laminations (L) that form the core (4) and the single rotor lamination (L) with stoppers (12) thereon can be produced as a group in a single shearing - bending mould (K2).

[0029] During the production of the rotor (3) 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 the core (4) is grouped by disposing the rotor lamination (L) having stoppers (12) thereon in the open position at the very end of the core (4) on the side of the second surface (11). After the core (4) is placed in the injection mould (Kl), aluminum is injected from the first surface (9). Firstly, the first end ring (10) is formed on the first surface (9) by the injected aluminum material and afterwards the conductor bars (8) are formed by allowing aluminum to flow into the rotor slots (7). The aluminum injected into the core (4) goes out from the rotor slots (7) of the rotor lamination (L) on the second surface (11) enabling to form the second end ring (110). Since the stoppers (12) of the rotor lamination (L) at the second surface (11) are in the outwards folded position, the magnets (5) can easily be inserted into the magnet inserting holes (6). After the magnets (5) are secured, the stoppers (12) are folded over the magnet inserting holes (6) preventing the displacement of the magnets

(5). In the rotor (3) of the present invention, the displacement of the magnets (5) inserted into the magnet inserting holes (6) in the core (4) after the aluminum injection process is prevented by means of the stoppers (12) formed on one rotor lamination (L) situated at the end of the rotor laminations (L) forming the core (4), the use of an additional element is not required for preventing the displacement of the magnets (5) and the problem of balance that might be caused by the additional elements is avoided.