SYNCHRONOUS ELECTRIC MOTOR

The present invention relates to mounting of a permanent magnet in the rotor of a hybrid synchronous line-start electric motor, it thus relates to a construction and manufacture of the rotor of a synchronous line-start electric motor with a squirrel cage and permanent magnets arranged in the rotor and mounted with two internal circlips according to standard DIN472 (60).

Known solutions are disclosed in patent documents US 6,954,018 B2; US 5,350,958 A; US 5,581,140 A; US 5,936,323 A; US 6,727,627 Bl, yet all these solutions do not provide for a dismountable assembly of the rotor and permanent magnets. The solutions provided in these patents do not include a variant with an internal circlip of the invention.

The purpose and goal of the present patent is a solution to a construction of the rotor with permanent magnets, which solution comprises two internal circlips that ensure a non-reduced cross-section of the rotor core due to the selected mounting technique, independence of the cross-section and resistance of rotor squirrel case rings on the selected mounting technique of internal circlips, removal of all ferromagnetic impurities that are present or appear during technologic methods of rotor manufacture before mounting of permanent magnets, mounting of previously magnetized permanent magnets into the rotor core after the whole rotor is manufactured and all mechanical treatments of rotor performed, mounting of internal circlips without any intervention into the cross-section of the rotor core, dismountable coupling rotor- magnets and therewith allows servicing, i. e. replacement of rotor magnets without a use of any technological methods, ecologic rotor decomposition, i. e. separation of permanent magnets from the remaining components or rotor assembly without any demanding disassembly techniques or energy consuming methods and optionally by using spring or other support plates in order to do away with the clearance due to manufacturing tolerances between the rotor core length and the length of permanent magnets. The task of the invention is solved by the independent patent claim.

The invention is described and presented on an embodiment and the accompanying drawings, representing in:

Figure 1 : elevation of a motor rotor with changed squirrel cage ring adapted for the mounting of a magnet and an internal circlip,

Figure 2: cross-section of the rotor core showing a groove for the circlip,

Figure 3: rotor assembly with magnets secured with an internal circlip,

Figure 4: rotor assembly with magnets secured with an internal circlip and a spring washer.

Motor rotor consists of a laminated rotor core 1 adapted in form to the core shape by means of a welding process and/or by means of interlocking ribs and/or mutually glued lamellas and/or lamellas mutually coupled with another binder. The core 1 of the rotor has a multitude of rotor grooves 2, into which electric conductors from copper profiles are inserted or moulded by pressure moulding of aluminium or other electrically conductive aluminium alloys. Copper or aluminium rotor conductors are mutually connected on both front rotor surfaces with a squirrel cage panel or a squirrel cage ring 4. Into the rotor core 1 a multitude of permanent magnets 5 is inserted in axial direction into additional grooves 3. Said permanent magnets 5 can have optional geometry, magnet quality and geometric orientation. The magnets 5 are cantered in axial direction along the laminated rotor core 1 by means of grooves 3. At least at one, optionally also at both ends of the rotor, the squirrel cage ring 4 may be shaped in a way to allow for the insertion of the magnets 5 into the grooves 3. Simultaneously, in the cage section in front of the grooves for the magnets, i. e. on places without grooves for magnets and where the cage can have a smaller diameter, a groove 10 is provided, preferably according to DIN 472 for an internal circlip 6 according to the same standard with respect to the available rotor diameter. The groove 10 has a dimension and shape to be able to receive the internal circlip 6. The same detail is provided at one or both ends of the rotor. The internal circlip 6, preferably according to DIN 472 prevents the magnets 5 from moving in axial direction or from falling out of the rotor. In case of too huge axial clearance due to different coefficients of linear temperature expansions and related dilatations and/or manufacturing tolerances of the length of the rotor core 1 and the magnets 5, two spring washers 7 can be inserted below the internal circlips 6, i. e. in the space between the two circlips 6 and the magnets 5. These spring washers 7 do away with the possible axial clearance of the magnets. The groove 10 in this case is adequately wider in order to be able to receive the circlip 6 and the washer 7. A further spring washer will not be needed in a majority of cases, as the proper position of the magnets will be ensured by their magnetic force. The rotor centre in axial direction is provided with a bore hole for a rotor shaft 8. The bore hole for the rotor shaft 8 can be extended at one side or at both sides in order to allow for the installation of the rotor onto the shaft, at which one or both motor bearings are arranged in the region 9 (counter bore holes) below the core 1 of the rotor. In these cases, in the region of increased rotor bore holes the cross-section of the laminated rotor core 1 is magnetically-conductively decreased to the minimum allowed.

In case only one circlip is used, the magnets are limited at the opposite side in known ways with the construction of the rotor core itself.

The mounting of the invention is therefore characterized in that the magnets 5 are freely inserted into the grooves 3 of the rotor and their movement in axial direction is at least at one side of the rotor core 1 limited by the internal circlip 6 inserted into the circlip 6 and optionally by the groove 10 adapted to the spring washer 7, wherein the groove 10 is provided in the cage section in front of the grooves for the magnets 5.

The locking of the grooves 3 for permanent magnets with inserted magnets 5 by use of the internal circlips 6 of the invention is applicable on all rotors, in which permanent magnets are arranged as an independent rotor part.