# US 7,612,481 B2 · Rotor with a cover plate for securing a magnet in the rotor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,612,481 B2 - Document ID: US7612481B2 - Status: Granted - Kind: B2 - Application number: 11/312,957 - Filed: 2005-12-19 - Published: 2006-07-20 - Granted: 2009-11-03 - Earliest claimed: 2004-12-20 - Assignees: Danfoss Compressors GmbH - Inventors: Niels Christian Weihrauch; Peter Scavenius Andersen - Web page: https://patentgrep.com/patent/US7612481B2 ## CPC - H02K 21/46: Motors having additional short-circuited winding for starting as an asynchronous motor - H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53}) ## Abstract The invention provides a rotor for an electrical motor, e.g. a line-start motor. The rotor comprises a magnet located in a cavity in a rotor core. The core is laminated from sheets of magnetically conductive material and the magnet is secured in the cavity by an end plate which covers the end face. To avoid short circuiting of the magnet, an aperture is provided in the end plate such that a first portion of the opening into the cavity is in communication with the aperture and such that a 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 center axis. ## Claims ### Claim 1 A rotor for rotation about a centre axis in an electrical motor, the rotor comprising: a core made of a magnetically conductive material, a magnet located in a cavity in the core, the cavity having a first cross-sectional area and allows insertion of the magnet into the cavity via an opening in an end face of the core, and an end plate which covers the end face, the end plate having an aperture with a second cross-sectional area, wherein aperture is provided such that a first portion of the opening into the cavity is in communication with the aperture and such that a 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. ### Claim 2 (depends on 1) The rotor according to claim 1, wherein the first portion constitutes at least 50 percent of the cross sectional area of the opening into the cavity. ### Claim 3 (depends on 1) The rotor according to claim 1, wherein the end plate has a circular outer peripheral rim. ### Claim 4 (depends on 1) The rotor according to claim 1, further comprising a squirrel cage with axially opposite short circuit rings, and wherein the end plate has a smaller radial size than the radial size of the short circuit ring and a shape which matches an inner surface of the short circuit ring. ### Claim 5 (depends on 1) The rotor according to claim 1, wherein the second area is equal to, or larger than the first area. ### Claim 6 (depends on 1) The rotor according to claim 1, wherein the aperture is arch shaped. ### Claim 7 (depends on 1) The rotor according to claim 1, comprising a plurality of magnets and wherein the end plate comprises a plurality of apertures. ### Claim 8 (depends on 6) The rotor according to claim 6, wherein the arch-shaped aperture(s) define(s) an arched radial outer peripheral edge and an arched radial inner peripheral edge, and wherein one of the magnets is secured in the cavity by the inner peripheral edge, and an adjacent magnet is secured in the cavity by the outer peripheral edge. ### Claim 9 (depends on 1) The rotor according to claim 1, wherein the end plate is made from a magnetically conductive material. ### Claim 10 (depends on 1) The rotor according to claim 1, wherein the end plate is made from the same material as the rotor. ### Claim 11 (depends on 1) The rotor according to claim 1, wherein the end plate has a peripheral rim with a first rim portion and a second rim portion forming different radial distances to the centre axis. ### Claim 12 A method of making a rotor comprising: a core made of a magnetically conductive material, a magnet located in a cavity in the core, the cavity having a first cross-sectional area and allowing insertion of the magnet into the cavity via an opening in an end face of the core, and an end plate which covers the end face, the end plate having an aperture with a second cross-sectional area the method being characterised in that aperture is provided such that a first portion of the opening into the cavity is in communication with the aperture and such that a 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. ### Claim 13 (depends on 12) The method according to claim 12, wherein the aperture is provided at least in the size of the first cross-sectional area.