# US 2013/0154426 A1 · Rotor for a Line Start Permanent Magnet Machine

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- Number: US 2013/0154426 A1
- Document ID: US20130154426A1
- Status: Published application
- Kind: A1
- Application number: 13/329,814
- Filed: 2011-12-19
- Published: 2013-06-20
- Earliest claimed: 2011-12-19
- Assignees: Baldor Electric Company
- Inventors: Mike Melfi; Rich Schiferl; Stephen Umans
- Web page: https://patentgrep.com/patent/US20130154426A1

## CPC

- H02K 21/46: Motors having additional short-circuited winding for starting as an asynchronous motor
- H02K 1/223: {Rotor cores with windings and permanent magnets (for additional excitation in synchronous motors or generators H02K21/042; in synchronous motors having additional short-circuited winding for starting as an asynchronous motor H02K21/46)}
- H02K 1/276: Magnets embedded in the magnetic core, e.g. interior permanent magnets [IPM]
- H02K 2213/03: Machines characterised by numerical values, ranges, mathematical expressions or similar information
- H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53})

## Abstract

A rotor comprises laminations with a plurality of rotor bar slots with an asymmetric arrangement about the rotor. The laminations also have magnet slots equiangularly spaced about the rotor. The magnet slots extend near to the rotor outer diameter and have permanent magnets disposed therein creating magnetic poles. The magnet slots may be formed longer than the permanent magnets disposed therein and define one or more magnet slot apertures. The permanent magnets define a number of poles and a pole pitch. The rotor bar slots are spaced from adjacent magnet slots by a distance that is at least 4% of the pole pitch. Conductive material is disposed in the rotor bar slots, and in some embodiments, may be disposed in the magnet slot apertures.

## Claims

### Claim 1

An electrical machine comprising:
a stator;
a rotor core disposed within the stator;
the rotor core comprising a plurality of generally like laminations stacked end to end to form a contiguous rotor core, the rotor core being rotatable relative to the stator about a center axis, the rotor core having an outer diameter (DR), each of the laminations having:
a plurality of magnet slots being spaced radially inward of the rotor outer diameter with an end of the magnet slots being adjacent to the rotor outer diameter and extending generally inward toward the rotor center axis, the magnet slots having permanent magnets disposed therein, the permanent magnets disposed in the magnet slots defining a number of poles (P) for the machine, a pole pitch (pp) for the machine wherein the pole pitch (pp)=(π×DR)/(P), the magnets defining a general axis of magnetization of each pole of the rotor, edges of the magnet slots that face the general axis of magnetization defining a saturation boundary area; and
a plurality of rotor bar slots spaced about the rotor core center axis, each of the rotor bar slots being radially inward of the rotor outer diameter with an end of the rotor bar slot being adjacent to the rotor outer diameter, the plurality of rotor bar slots having an asymmetric angular spacing about the rotor core;
wherein the rotor bar slots disposed in the saturation boundary area are spaced from an adjacent magnet slot by a distance that is at least four percent of the pole pitch (“pp”);
conductive material disposed in the rotor bar slots; and
end members disposed on axial opposite ends of the rotor core, the end members being in electrical contact with the conductive material.

### Claim 2 (depends on 1)

The machine of claim 1 wherein the magnet slots form a generally V-shape.

### Claim 3 (depends on 2)

The machine of claim 2 wherein the V-shape comprises an obtuse angle.

### Claim 4 (depends on 1)

The machine of claim 1 wherein two or more of the rotor bar slots in the saturation boundary area have a radially inward edge which defines a reference plane generally parallel to an adjacent magnet.

### Claim 5 (depends on 1)

The machine of claim 1 wherein at least one of the rotor bar slots in the saturation boundary area has a radially inward edge which conforms generally to the shape of an adjacent magnet.

### Claim 6 (depends on 1)

The machine of claim 1 wherein all of the rotor bar slots in the saturation boundary area are spaced from their respective adjacent magnet slots at substantially the same distance.

### Claim 7 (depends on 1)

The machine of claim 1 wherein the magnet slots form a generally U-shape.

### Claim 8 (depends on 1)

The machine of claim 1 wherein adjacent laminations are skewed relative to a line parallel to the rotor center axis.

### Claim 9 (depends on 1)

The machine of claim 1 wherein the conductive material comprises bars extending through the rotor bar slots.

### Claim 10 (depends on 1)

The machine of claim 1, wherein the conductive material is cast through the rotor bar slots along with forming the end members.

### Claim 11 (depends on 1)

The machine of claim 1 wherein the ends of the rotor bar slots are formed in the lamination adjacent the outer diameter at substantially the same distance.

### Claim 12 (depends on 1)

The machine of claim 1 wherein the magnet slots are longitudinally longer than the permanent magnets disposed therein and define at least one magnet slot aperture between an end of the permanent magnet and the magnet slot.

### Claim 13 (depends on 12)

The machine of claim 12, wherein conductive material is disposed in the magnet apertures.

### Claim 14 (depends on 1)

The machine of claim 1, wherein the rotor bar slots disposed outside of the saturation boundary are spaced from an adjacent magnet slot by a distance that is at least four percent of the pole pitch.

### Claim 15

A machine comprising:
a rotor with laminations having a plurality of magnets slots radially inward of a peripheral edge of the rotor, the rotor peripheral edge defining a rotor outer diameter (Dr), the magnets slots having magnets disposed therein, the magnets defining a number of poles (P) of the machine and a pole pitch (pp) for the machine wherein the pole pitch (pp)=(π×Dr)/(P), the magnets defining a general axis of magnetization of each pole of the rotor, edges of the magnet slots that face the general axis of magnetization defining a saturation boundary area, the rotor further comprising a plurality of rotor bar slots, a first portion of the rotor bar slots being disposed in the saturation boundary area and having a first angular spacing between the rotor bar slots comprising the first portion, a second portion of the rotor bar slots having a second angular spacing between the rotor bar slots comprising the second portion, the first angular spacing being different from the second angular spacing, the rotor bar slots disposed in the saturation boundary area being spaced from an adjacent magnet slot by a distance that is at least four percent of the pole pitch, the rotor further comprising conductive material disposed in the rotor bar slots; and
end members on axial ends of the rotor in electrical communication with the conductive material in the rotor bar slots.

### Claim 16 (depends on 15)

The machine of claim 15 wherein the magnet slots form a generally V-shape.

### Claim 17 (depends on 16)

The machine of claim 16 wherein the V-shape comprises an obtuse angle.

### Claim 18 (depends on 15)

The machine of claim 15 wherein two or more of the rotor bar slots in the saturation boundary area have a radially inward edge which defines a reference plane generally parallel to an adjacent magnet slot.

### Claim 19 (depends on 15)

The machine of claim 15 wherein at least one of the rotor bar slots in the saturation boundary area has a radially inward edge which conforms generally to the shape of an adjacent magnet slot.

### Claim 20 (depends on 15)

The machine of claim 15 wherein the rotor bar slots in the saturation boundary area are spaced from their respective adjacent magnet slots at substantially the same distance.

### Claim 21 (depends on 15)

The machine of claim 15 wherein the magnet slots define a generally U-shape.

### Claim 22 (depends on 15)

The machine of claim 15 wherein adjacent laminations are skewed relative to an axis parallel to the rotor center axis.

### Claim 23 (depends on 15)

The machine of claim 15 wherein the conductive material comprises bars extending through the rotor bar slots.

### Claim 24 (depends on 15)

The machine of claim 15 wherein the conductive material is cast through the rotor bar slots along with forming the end members.

### Claim 25 (depends on 15)

The machine of claim 15 wherein the rotor bar slots of the first portion each have a different shape.

### Claim 26 (depends on 15)

The machine of claim 15 wherein the magnets are disposed in the magnets slots in a manner such that magnets are spaced from an end of the magnet slot adjacent the rotor peripheral edge and form a magnet slot aperture.

### Claim 27 (depends on 26)

The machine of claim 26 wherein conductive material is disposed in the magnet aperture.

### Claim 28 (depends on 15)

The machine of claim 15 wherein the rotor bar slots disposed outside of the saturation boundary are spaced from an adjacent magnet slot by a distance that is at least four percent of the pole pitch.