GB2141290A

GB2141290A - Improvements in and relating to induction motors

Info

Publication number: GB2141290A
Application number: GB08406328A
Authority: GB
Inventors: James Millington
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-03-10
Filing date: 1984-03-07
Publication date: 1984-12-12
Also published as: GB2141290B; GB8406328D0

Abstract

A rotor disc for an induction motor has inner and outer concentric rows 21, 22 respectively for core slots 23 of generally circular shape. The slots 23 of the inner row 21 and the outer row 22 may be radially aligned or offset (Fig. 4) relative to each other. The slots 23 may be arranged in groups of three and five around the disc (Fig. 3) and the outer slots may be larger than the inner slots (Fig. 6) <IMAGE>

Description

SPECIFICATION Improvements in and relating to induction motors This invention concerns improvements in and relating to induction motors.

Induction motors comprise a rotor and a stator.

The stator has wire windings through which are passed electric current. The rotor has a plurality of slots therethrough which contain metal cores usually of aluminium or copper. The field produced by the electric current acts on the metal cores of the rotor causing itto rotate.

The rotor is usually a laminate of discs each disc having a circular arrangement of generally rectangular slots for the metal cores. The outer ends of the slots are in fact normally arcuate.

These rotors can be difficult and expensive to manufacture in view of the shape of the slots called for and hence the cores to be shot into the slots.

This invention seeks to provide a rotor disc which may be easier and less expensive to manufacture and which also may be used to produce a more efficient induction motor.

It has now been found that manufacture of rotor discs can be made easier and the efficiency of an induction motor containing such rotor discs improved by providing the rotor discs with generally circular core slots arranged in one or more substantially concentric rows.

The circular core slots may be arranged in a variety of configurations say equally spaced in each of two concentric rows, each slot of the inner row being radially aligned with a slot of the outer row.

Alternatively, the slots of each row could be arranged in groups of three and five around the disc.

Another alternative for two rows of slots is for the slots of each row to be offset relative to each other.

For any of these proposals, the slots of the inner and outer rows may be of the same size or one of the rows may have larger slots, usually the outer row.

For a single row of slots, they may be evenly spaced or may be arranged in groups, say of six slots, spaced from each other by more than the gap between each slot of a group.

A rotor disc of the invention may be made by stamping out the slots from a metal, usually high permeability electrical sheet steel disc. A rotor is then constructed as a laminate of the discs on a rotor shaft, usually of steel with the slots slightly offset relative to each other to form spiral passages into which are shot metal cores, usually of aluminium or copper.

The proposals of this invention enable the intro duction of more metal cores giving a greater surface area of metal core in an induction motor without weakening the discs. This can result in lower operating temperatures for an induction motor and greater efficiency.

The invention also provides an induction motor having a rotor made up of rotor discs of the invention.

This invention will now be further described, by way of example only, with reference to the accom panying drawings, in which: Figure 1 shows a prior art induction motor rotor disc stamping; Figure 2 shows enlarged part of a first rotor disc stamping of the invention; Figure 3 shows enlarged a second rotor disc stamping of the invention; Figure 4 shows enlarged part of a third rotor disc stamping of the invention; Figure 5shows enlarged a fourth rotor disc stamping of the invention; and Figure 6 shows enlarged part of a fifth rotor disc stamping of the invention.

Referring to Figure la a rotor disc stamping 10 of electrical sheet steel has thirty four circumferentially arranged elongate slots 12. The slots 12 cores are approximately 0.3 x 0.08 inches and a total surface area of approximately 0.86 square inches.

In Figure 2 a rotor disc 20 has concentrically arranged an inner row 21 and an outer row 22 of thirty four circular equally spaced slots 23. The slots 23 are each of diameter 0.13 inches and the rows are separated by about 0.063 inches but could be closer, say 0.04 inches apart. The total surface area of the slots 23 is approximately 0.9 square inches which is, of course, greater than the surface area provided by the prior art discs.

The Figure 3 proposal is a disc 30 having concentrically arranged an inner row 31 and an outer row 32 of circular slots 33. Each row has thirty two slots 33 arranged in alternate groups 34 and 35 of three and five slots respectively. The gap between each group is greater than that between each slot of a group and the gap between each slot of a group is the same.

In Figure 4 a rotor disc 40 has concentrically arranged inner 41 and outer 42 rows of thirty four circular slots 43 each. Unlike the proposals of Figure 2, however, slots of each row are not radially aligned but are radially offset relative to each other by about 0.063 inches.

The proposal of Figure 5 is a disc 50 having only one circumferential row 51 of circular slots 52. The slots 52 are, however, arranged in alternate groups 53 and 54 of four and two slots respectively. Each group 53,54 is separated by approximately 0.17 inches but each slot 52 of a group by about 0.063 inches.

Referring to Figure 6 a rotor disc 60 has concentrically arranged radially aligned inner 61 and outer 62 rows of thirty four circular slots 63 each. The outer slots 63b are of greater diameter than the inner slots 63a. The diameter of slots 63a is about 0.11 inches and that of slots 63b about 0.16 inches giving a total surface area covered by both rows of slots of about 0.97 square inches. The slots of each row are approximately 0.06 inches apart circumferentially.

Although the invention has been described with reference to several specific embodiments, it should be appreciated that many other slot arrangements in rotor discs may fulfill the requirements of the invention.

1. A rotor disc for an induction motor, the disc having generally circular core slots arranged in one

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in and relating to induction motors This invention concerns improvements in and relating to induction motors. Induction motors comprise a rotor and a stator. The stator has wire windings through which are passed electric current. The rotor has a plurality of slots therethrough which contain metal cores usually of aluminium or copper. The field produced by the electric current acts on the metal cores of the rotor causing itto rotate. The rotor is usually a laminate of discs each disc having a circular arrangement of generally rectangular slots for the metal cores. The outer ends of the slots are in fact normally arcuate. These rotors can be difficult and expensive to manufacture in view of the shape of the slots called for and hence the cores to be shot into the slots. This invention seeks to provide a rotor disc which may be easier and less expensive to manufacture and which also may be used to produce a more efficient induction motor. It has now been found that manufacture of rotor discs can be made easier and the efficiency of an induction motor containing such rotor discs improved by providing the rotor discs with generally circular core slots arranged in one or more substantially concentric rows. The circular core slots may be arranged in a variety of configurations say equally spaced in each of two concentric rows, each slot of the inner row being radially aligned with a slot of the outer row. Alternatively, the slots of each row could be arranged in groups of three and five around the disc. Another alternative for two rows of slots is for the slots of each row to be offset relative to each other. For any of these proposals, the slots of the inner and outer rows may be of the same size or one of the rows may have larger slots, usually the outer row. For a single row of slots, they may be evenly spaced or may be arranged in groups, say of six slots, spaced from each other by more than the gap between each slot of a group. A rotor disc of the invention may be made by stamping out the slots from a metal, usually high permeability electrical sheet steel disc. A rotor is then constructed as a laminate of the discs on a rotor shaft, usually of steel with the slots slightly offset relative to each other to form spiral passages into which are shot metal cores, usually of aluminium or copper. The proposals of this invention enable the intro duction of more metal cores giving a greater surface area of metal core in an induction motor without weakening the discs. This can result in lower operating temperatures for an induction motor and greater efficiency. The invention also provides an induction motor having a rotor made up of rotor discs of the invention. This invention will now be further described, by way of example only, with reference to the accom panying drawings, in which: Figure 1 shows a prior art induction motor rotor disc stamping; Figure 2 shows enlarged part of a first rotor disc stamping of the invention; Figure 3 shows enlarged a second rotor disc stamping of the invention; Figure 4 shows enlarged part of a third rotor disc stamping of the invention; Figure 5shows enlarged a fourth rotor disc stamping of the invention; and Figure 6 shows enlarged part of a fifth rotor disc stamping of the invention. Referring to Figure la a rotor disc stamping 10 of electrical sheet steel has thirty four circumferentially arranged elongate slots 12. The slots 12 cores are approximately 0.3 x 0.08 inches and a total surface area of approximately 0.86 square inches. In Figure 2 a rotor disc 20 has concentrically arranged an inner row 21 and an outer row 22 of thirty four circular equally spaced slots 23. The slots 23 are each of diameter 0.13 inches and the rows are separated by about 0.063 inches but could be closer, say 0.04 inches apart. The total surface area of the slots 23 is approximately 0.9 square inches which is, of course, greater than the surface area provided by the prior art discs. The Figure 3 proposal is a disc 30 having concentrically arranged an inner row 31 and an outer row 32 of circular slots 33. Each row has thirty two slots 33 arranged in alternate groups 34 and 35 of three and five slots respectively. The gap between each group is greater than that between each slot of a group and the gap between each slot of a group is the same. In Figure 4 a rotor disc 40 has concentrically arranged inner 41 and outer 42 rows of thirty four circular slots 43 each. Unlike the proposals of Figure 2, however, slots of each row are not radially aligned but are radially offset relative to each other by about 0.063 inches. The proposal of Figure 5 is a disc 50 having only one circumferential row 51 of circular slots 52. The slots 52 are, however, arranged in alternate groups 53 and 54 of four and two slots respectively. Each group 53,54 is separated by approximately 0.17 inches but each slot 52 of a group by about 0.063 inches. Referring to Figure 6 a rotor disc 60 has concentrically arranged radially aligned inner 61 and outer 62 rows of thirty four circular slots 63 each. The outer slots 63b are of greater diameter than the inner slots 63a. The diameter of slots 63a is about 0.11 inches and that of slots 63b about 0.16 inches giving a total surface area covered by both rows of slots of about 0.97 square inches. The slots of each row are approximately 0.06 inches apart circumferentially. Although the invention has been described with reference to several specific embodiments, it should be appreciated that many other slot arrangements in rotor discs may fulfill the requirements of the invention. CLAIMS

1. A rotor disc for an induction motor, the disc having generally circular core slots arranged in one or more substantially concentric rows.

2. A rotor disc as claimed in claim 1, wherein the core slots are equally spaced in each of inner and outer concentric rows, each slot of the inner row being radially aligned with a slot of the outer row.

3. A rotor disc as claimed in claim 1, wherein-the core slots of the or each row are arranged in-spaced groups.

4. A rotordisc as claimed in claim 3, wherein the core slots are arranged in groups of three and five around the disc.

5. A rotor disc as claimed in claim 1, wherein the core slots are in two concentric rows, the slots of each row being offset relative to the other.

6. A rotor disc as claimed in any one of claims 1 to 5, wherein the slots of inner and outer rows are of the same size.

7. A rotor disc as claimed in any one of claims 1 to 5, wherein the slots of one row are of a different size to the slots of the or each other row.

8. A rotor disc as claimed in claim 7, wherein the core slots of the outer row are larger than those of the or each inner row.

9. A rotor disc as claimed in claim 1, having a single row of core slots arranged in groups, each group being spaced apart more than the space between any two slots of a group.

10. Arotorforan induction motor, the rotor being made up of a plurality of rotor discs as claimed in any one of claims 1 to 9.

11. An induction motor having a rotor as claimed in claim 10.

12. A rotor disc substantially as-hereinbefore described with referenceto and as illustrated in any one of Figures 2 to 6 of the accompanying drawings.