Rotor for an electrical motor
The invention provides a rotor for an electrical motor, a tool for making a rotor core and a method of making the rotor. The rotor could be incorporated e.g. in a line-start motor and comprises a squirrel cage and magnet located in a rotor core. The magnets are, in one end of the rotor, secured by an end plate with apertures which are larger than the magnet openings, and the end plate is indexed relative to the magnet slots such that a first portion of openings into the magnet slots is in communication with the aperture and such that a remaining, second, portion of the magnet slots is covered by the end plate. In one aspect, the end plate forms an integrated part of the rotor core and comprises openings cooperating with conductor slots to form through-going passages for conductors of the squirrel cage. In that way, the end plate is held in a completely fixed position by the squirrel cage which is moulded directly onto the core and into the conductor slots.
1. A rotor for an electrical motor, the rotor comprising:
a core made from a stack of sheets each comprising conductor openings and magnet openings which, in combination with corresponding openings of the other sheets in the stack, form conductor slots and magnet slots extending between first and second axially opposite end faces of the rotor,
an end plate which is provided with an aperture,
wherein the aperture is larger than the magnet openings, and the end plate is indexed relative to the magnet slots such that a first portion of openings into the magnet slots is in communication with the aperture and such that a remaining, second, portion of the magnet slots is covered by the end plate.
2. The rotor according to daim 1 , further comprising a squirrel cage comprising axially oppositely located short circuit rings connected by conductors moulded into the conductor slots, and wherein the end plate comprises conductor openings which cooperate with the conductor slots to allow the conductors to extend through the conductor openings of the end plate.
3. The rotor according to claim 1 , wherein the aperture are arched.
4. The rotor according to daim 3 , wherein the aperture is provided such that the first portion of the opening into the cavity is in communication with the aperture and such that the remaining, second, portion of the cavity is covered by the end plate to secure the magnet in the cavity independently upon the orientation of the end plate around the centre axis.
5. The rotor according to claim 1 , wherein the end plate is joined with the sheets by interlocking.
6. The rotor according to claim 1 , wherein the sheets and the end plate is made from the same sheet material.
7. An interlocking tool for making a rotor, said tool comprising:
punching means for making sheets each comprising conductor openings and magnet openings,
punching means for making an end plate,
stacking means adapted to:
stack the sheets such that the conductor openings and magnet openings of a plurality of sheets in combination form condudor slots and magnet slots extending between first and second axially opposite end faces of the rotor, and
position the end plate at one end face of the stack of sheets such that a first portion of openings into the magnet slots is in communication with the aperture and such that a remaining, second, portion of the magnet slots is covered by the end plate.
8. The interlocking tool according to claim 7 wherein the punching means for making the end plate comprises means for making conductor openings in the end plate, and wherein the stacking means further comprises means for joining the sheets and the end plate to form one single rotor core component.
9. A method of making a rotor, wherein a core is formed by interlocking plates of a sheet material, wherein each plate in the stack comprises condudor openings and magnet openings to form longitudinally extending condudor slots and magnet slots, and wherein an end plate of the stack is formed with an aperture positioned such that a first portion of openings into the magnet slots is in communication with the aperture and such that a remaining, second, portion of the magnet slots is covered by the end plate.
10. The method according to daim 9 , wherein the sheets and the end plate is produced and staked to form one single rotor core component in an interlocking process.