GB2082847A - Variable Reluctance Motor - Google Patents

Variable Reluctance Motor Download PDF

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Publication number
GB2082847A
GB2082847A GB8026890A GB8026890A GB2082847A GB 2082847 A GB2082847 A GB 2082847A GB 8026890 A GB8026890 A GB 8026890A GB 8026890 A GB8026890 A GB 8026890A GB 2082847 A GB2082847 A GB 2082847A
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GB
United Kingdom
Prior art keywords
stator
rotor
laminations
shields
motor system
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB8026890A
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GB2082847B (en
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Chloride Group Ltd
Original Assignee
Chloride Group Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Chloride Group Ltd filed Critical Chloride Group Ltd
Priority to GB8026890A priority Critical patent/GB2082847B/en
Publication of GB2082847A publication Critical patent/GB2082847A/en
Application granted granted Critical
Publication of GB2082847B publication Critical patent/GB2082847B/en
Expired legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K19/00—Synchronous motors or generators
    • H02K19/02—Synchronous motors
    • H02K19/04—Synchronous motors for single-phase current
    • H02K19/06—Motors having windings on the stator and a variable-reluctance soft-iron rotor without windings, e.g. inductor motors
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K1/00—Details of the magnetic circuit
    • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K3/00—Details of windings
    • H02K3/42—Means for preventing or reducing eddy-current losses in the winding heads, e.g. by shielding

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Synchronous Machinery (AREA)

Abstract

This invention is an arrangement for reducing eddy current losses in a variable reluctance motor for propulsion of a vehicle from a battery. Shields of material of lower resistivity than the rotor and stator laminations are located adjacent the end magnetic laminations of the stator and/or rotor to inhibit eddy currents in the magnetic laminations due to axial flux. Alternatively, or in addition, shielding laminations may be inserted at intermediate points in the lamination stack. Materials and dimensions are exemplified.

Description

SPECIFICATION Variable Reluctance Electric Motor Systems This invention relates to variable reluctance electric motor systems and an object of the invention is to improve the efficiency of such a system.
According to the present invention, a variable reluctance electric motor system including a motor having a laminated salient pole stator with energising windings, and a laminated salient pole rotor with no windings, and means for supplying to the stator windings, pulses of current synchronised with the rotation of the rotor to vary the flux in each stator pole without reversing it, is characterised by shields of material of low resistivity in the form of plates located adjacent to the end magnetic laminations of the stator and/or rotor to inhibit eddy currents in the magnetic laminations due to axial flux.
The shields may be of any material having a low resistivity compared with that of the magnetic laminations but in practice will normally be of copper, brass or aluminium. Conveniently a shield is located against each end lamination of the rotor stack, and each lamination of the stator stack. The shields may be of the same form as the rotor and/or stator laminations, or they may be simple discs or they may have other shapes as appropriate, the stator shields being located within the axial length of the windings.
Aiternatively, or in addition, shielding laminations may be inserted at intermediate points in the magnetic lamination stack.
Shields may have different thicknesses but typically will be thicker than the ferrous rotor or stator laminations by perhaps one order of magnitude, or more.
Variable reluctance motors may often be used in applications where it is particularly desirable to minimise losses. For example, in a battery propelled vehicle, it is of the first importance to avoid loss of electric power from the battery.
Since such a motor relies on changes of flux through the whole magnetic circuit in order to produce power, changes of flux perpendicular to the laminations may produce eddy currents which in the comparatively resistive ferrous material represent an appreciable loss of energy. This can be reduced by a redistribution of eddy current such that a high proportion exists in the shields of high conductivity.
The invention may be applied to a wide variety of motors, but one specific embodiment will be very briefly described by way of example.
In this particular motor, the rotor has six poles, and no windings, and the stator has eight poles with a four-phase set of windings to which pulses of current are supplied from solid state switching means synchronized with the rotation of the rotor.
These may be of any preferred type for example as described in British Patent Specification No.
13415/77 Case EPS 236.
The external diameter of the rotor and the internal diameter of the stator is about 1 30mm, and each magnetic stack comprises between 300 and 400 laminations of high permeability ferrous material about .35 mm thick. At each end of each of the stator and rotor stacks there is a shield lamination. The shield laminations of the stator are of the same shape as the magnetic laminations. Those of the rotor are disc-shaped with an outer diameter equal to that of the rotor magnetic laminations. A shield lamination is of cooper and is of a thickness of about 5mm.
Thus, in operation the shield laminations offer a low resistance path to eddy currents, thereby substantially reducing the eddy currents in the magnetic laminations of greater resistivity while themselves evolving substantially less heat, and reducing losses of power.
The invention is not limited to the details of the specific embodiment, and in some cases shield laminations may be located at intermediate points within the stack of magnetic laminations, or wholly or partially removed from the end surface of the core, or only stator or rotor screens may be used.
The accompanying drawing is an end view of one form of the stator and rotor laminations.
Claims
1. A variable reluctance motor system including a motor having a laminated salient pole stator with energising windings, and a laminated salient pole rotor with no windings, and means for supplying to the stator winding pulses of current synchronised with the rotation of the rotor to vary the flux in each stator pole without reversing it, and including shields of material of low resistivity in the form of plates located adjacent to the end magnetic laminations of the stator and/or rotor to inhibit eddy currents in the magnetic laminations due to axial flux.
2. A motor system as claimed in Claim 1 in which the shields are of copper, brass or aluminium.
3. A motor system as claimed in either of the preceding claims in which a shield is located against each lamination of the rotor stack.
4. A motor system as claimed in any of the preceding claims in which a shield is located against each lamination of the stator stack.
5. A motor system as claimed in any of the preceding claims in which the shields are of the same form as the adjacent rotor or stator laminations.
6. A motor system as claimed in any of Claims 1-4 in which the shields are in the form of simple discs.
7. A motor system as claimed in any of the preceding claims in which stator shields are located within the axial length of the stator windings.
8. A motor system as claimed in any of the preceding claims in which shielding laminations are inserted at intermediate points in the stator and/or the rotor lamination stack.
9. A motor system as claimed in any of the preceding claims in which the shields are
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (11)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Variable Reluctance Electric Motor Systems This invention relates to variable reluctance electric motor systems and an object of the invention is to improve the efficiency of such a system. According to the present invention, a variable reluctance electric motor system including a motor having a laminated salient pole stator with energising windings, and a laminated salient pole rotor with no windings, and means for supplying to the stator windings, pulses of current synchronised with the rotation of the rotor to vary the flux in each stator pole without reversing it, is characterised by shields of material of low resistivity in the form of plates located adjacent to the end magnetic laminations of the stator and/or rotor to inhibit eddy currents in the magnetic laminations due to axial flux. The shields may be of any material having a low resistivity compared with that of the magnetic laminations but in practice will normally be of copper, brass or aluminium. Conveniently a shield is located against each end lamination of the rotor stack, and each lamination of the stator stack. The shields may be of the same form as the rotor and/or stator laminations, or they may be simple discs or they may have other shapes as appropriate, the stator shields being located within the axial length of the windings. Aiternatively, or in addition, shielding laminations may be inserted at intermediate points in the magnetic lamination stack. Shields may have different thicknesses but typically will be thicker than the ferrous rotor or stator laminations by perhaps one order of magnitude, or more. Variable reluctance motors may often be used in applications where it is particularly desirable to minimise losses. For example, in a battery propelled vehicle, it is of the first importance to avoid loss of electric power from the battery. Since such a motor relies on changes of flux through the whole magnetic circuit in order to produce power, changes of flux perpendicular to the laminations may produce eddy currents which in the comparatively resistive ferrous material represent an appreciable loss of energy. This can be reduced by a redistribution of eddy current such that a high proportion exists in the shields of high conductivity. The invention may be applied to a wide variety of motors, but one specific embodiment will be very briefly described by way of example. In this particular motor, the rotor has six poles, and no windings, and the stator has eight poles with a four-phase set of windings to which pulses of current are supplied from solid state switching means synchronized with the rotation of the rotor. These may be of any preferred type for example as described in British Patent Specification No. 13415/77 Case EPS 236. The external diameter of the rotor and the internal diameter of the stator is about 1 30mm, and each magnetic stack comprises between 300 and 400 laminations of high permeability ferrous material about .35 mm thick. At each end of each of the stator and rotor stacks there is a shield lamination. The shield laminations of the stator are of the same shape as the magnetic laminations. Those of the rotor are disc-shaped with an outer diameter equal to that of the rotor magnetic laminations. A shield lamination is of cooper and is of a thickness of about 5mm. Thus, in operation the shield laminations offer a low resistance path to eddy currents, thereby substantially reducing the eddy currents in the magnetic laminations of greater resistivity while themselves evolving substantially less heat, and reducing losses of power. The invention is not limited to the details of the specific embodiment, and in some cases shield laminations may be located at intermediate points within the stack of magnetic laminations, or wholly or partially removed from the end surface of the core, or only stator or rotor screens may be used. The accompanying drawing is an end view of one form of the stator and rotor laminations. Claims
1. A variable reluctance motor system including a motor having a laminated salient pole stator with energising windings, and a laminated salient pole rotor with no windings, and means for supplying to the stator winding pulses of current synchronised with the rotation of the rotor to vary the flux in each stator pole without reversing it, and including shields of material of low resistivity in the form of plates located adjacent to the end magnetic laminations of the stator and/or rotor to inhibit eddy currents in the magnetic laminations due to axial flux.
2. A motor system as claimed in Claim 1 in which the shields are of copper, brass or aluminium.
3. A motor system as claimed in either of the preceding claims in which a shield is located against each lamination of the rotor stack.
4. A motor system as claimed in any of the preceding claims in which a shield is located against each lamination of the stator stack.
5. A motor system as claimed in any of the preceding claims in which the shields are of the same form as the adjacent rotor or stator laminations.
6. A motor system as claimed in any of Claims 1-4 in which the shields are in the form of simple discs.
7. A motor system as claimed in any of the preceding claims in which stator shields are located within the axial length of the stator windings.
8. A motor system as claimed in any of the preceding claims in which shielding laminations are inserted at intermediate points in the stator and/or the rotor lamination stack.
9. A motor system as claimed in any of the preceding claims in which the shields are substantially thicker than the rotor and/or stator laminations.
10. A motor system constructed and arranged substantially as herein specifically described with reference to the accompanying drawings.
11. A motor system as claimed in any of the preceding claims arranged for propelling a vehicle and energised by a battery carried on the vehicle.
GB8026890A 1980-08-18 1980-08-18 Variable reluctance motor Expired GB2082847B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8026890A GB2082847B (en) 1980-08-18 1980-08-18 Variable reluctance motor

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB8026890A GB2082847B (en) 1980-08-18 1980-08-18 Variable reluctance motor

Publications (2)

Publication Number Publication Date
GB2082847A true GB2082847A (en) 1982-03-10
GB2082847B GB2082847B (en) 1984-07-25

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB8026890A Expired GB2082847B (en) 1980-08-18 1980-08-18 Variable reluctance motor

Country Status (1)

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GB (1) GB2082847B (en)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2149587A (en) * 1983-09-29 1985-06-12 Okuma Machinery Works Ltd Synchronous motors and control units thereof
GB2167910A (en) * 1984-10-19 1986-06-04 Kollmorgen Tech Corp Reluctance motors
US4993290A (en) * 1987-01-28 1991-02-19 Emerson Electric Co. Method of stamping rotor and stator laminations
US5128576A (en) * 1987-01-28 1992-07-07 Emerson Electric Co. Rotor assembly and motor construction and method of making same
US5432390A (en) * 1992-05-15 1995-07-11 Emerson Electric Co. Switched reluctance motor
SG81257A1 (en) * 1998-01-20 2001-06-19 Switched Reluctance Drives Ltd Noise reduction in reluctance machines

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2149587A (en) * 1983-09-29 1985-06-12 Okuma Machinery Works Ltd Synchronous motors and control units thereof
GB2167910A (en) * 1984-10-19 1986-06-04 Kollmorgen Tech Corp Reluctance motors
US4670696A (en) * 1984-10-19 1987-06-02 Kollmorgen Technologies Corporation Variable speed variable reluctance electrical machines
GB2167910B (en) * 1984-10-19 1989-06-01 Kollmorgen Tech Corp Variable speed variable reluctance electrical machines
US4993290A (en) * 1987-01-28 1991-02-19 Emerson Electric Co. Method of stamping rotor and stator laminations
US5128576A (en) * 1987-01-28 1992-07-07 Emerson Electric Co. Rotor assembly and motor construction and method of making same
US5432390A (en) * 1992-05-15 1995-07-11 Emerson Electric Co. Switched reluctance motor
SG81257A1 (en) * 1998-01-20 2001-06-19 Switched Reluctance Drives Ltd Noise reduction in reluctance machines

Also Published As

Publication number Publication date
GB2082847B (en) 1984-07-25

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PCNP Patent ceased through non-payment of renewal fee