GB2203293A

GB2203293A - Homopolar machine having high voltage/low current input/output

Info

Publication number: GB2203293A
Application number: GB08708091A
Authority: GB
Inventors: Bryan Nigel Victor Parsons
Original assignee: Jaguar Cars Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 1987-04-04
Filing date: 1987-04-04
Publication date: 1988-10-12
Also published as: GB8708091D0

Abstract

In order to provide a homopolar motor/generator which operates from/generates high voltage/low current, a transforming effect is provided by a primary conductive loop 21 and secondary winding 26 provided on the annular core 18, the primary conductive loop 21 being connected by means of brushes 24 and 25 to the sleeve 13 on the armature 12 field coils 19, 20 on the stator being connected to an a.c. supply. The homopolar generator/motor has a rotor 10 with an armature 12 made of ferromag- netic material and having a seal 13 made of material of good electrical conductivity secured around its outer periphery. The rotor 10 is surrounded by a ferromagnetic stator having a pair of end plates 16 and 17 and an annular core 18. A transmission system may include a homopolar generator and at least one homopolar motor, as described above. <IMAGE>

Description

HOHOPOLAR GEBERATOR/MOTOR The invention relates to a homopolar generator/motor and in particular to such generators or motors suitable for use in transmission of drive from a prine mover to a driven component, and to transmission systems including such generators and motors.

Conventional honopolar motors are capaole of producing high terques and are suitable for drivino, for example, the wheels of a motor vehicle. However, conventiona homopolai moters require a low voltage extremely high current DC supply, typically several thousand amps et about half a volt. Such DC supplies can Be produced by homopoler generators, but the problem then arises of transmitting the supply from the generator to the motor.

According to one aspect of the present invention a honopoiar generator or homopolar motor comprises a rotor having an armature made of ferronagnetic material, at least the outer circumferential portion of the armature being of good electrical conductivity, said rotor being surrouded by a ferromagnetic stator, field coils being prove by on the stator, said field coils being adapted to be connected to an alternating current supply and heing arranged to provide an alternating magnetic field which is substantially radial across said outer circumferential portion of the armaturefi said stator including an annular ferromagnetic core, a primary conductive loop being provided on the ferromagnetic core, said primary loop beinq connected by means of brushes at either end to axially spaced positions on said outer circunferential portion of the armature, and a secondary winding being provided on the ferromagnetic core.

.'itii the above arranoement, in the case of a generator, rotation of the conductive portion of the armature in t.e alternating magnetic field produced by the field coils, wi i ir,auce an extremely high alternating current at low voltage, in the conductive portion of the armature, parallel to the axis of the rotor. This alternating current is transferred to the primary loop on the iron core and will be transformed into a relatively high voltage low current alternating current in the secondary winding.This higii voltage low current alternating current may then be transmitted from the generator to a motor without difticulty.

The relatively high voltage low current alternating current produced by the generator may then be fed to the secondary winding on a homopolar motor of similar construction. The high voltage low current alternating current ill thereby be transformed back into a low voltage extremely high current alternatina current in the primary loop which is fed to the conductive portion of the armature via the drushes. Tie extremely high alternating current in the conductive portion of the armature in the presence of the alternating magnetic field produced by the field coils, will then cause the armature to rotate.

According to a further aspect of the present invention, a transtissòn sister includes; a homopolar generator of the consttuction herein before defined, said generator being orivingly connected to a prime mover; at least one domopolar motor of the construction herein before defined, said motor being drivingly connected to a driven component, the secondary winding of the generator being connected to the secondary winding of the motor; and a secondary source of alternating current which is connected to the field coils of the homopolar generator.

The secondary source of alternating current may be a further generator which is driven by the prime mover. This alternating current may also be used to energize the field coils of the motor, but alternatively power for the field coils of the motor may be tapped off the transformed current supplied by the homopolar generator.

In order to obtain maximun efficiency it will be necessary to ensure that the alternating magnetic field produced by field coils of the motor is in correct phase with the alternating current supplied by the homopolar generator.

This nay be achieved by suitable control logic.

Uith this transmission system, it would be possible to operate the prime mover at a speed which is most efficient for the power output required. The speed of the e driver: components may then be controlled by variation of the magnets field trengths produced by the field coils of the generator end/or motor by varying the current e;ergising these field coils. Alternatively, the output of the rotors ozulo be controlled by variation of the phases of the magnetic field produced by the field coils thereof and. the alterntting current supplied by the homopolar generator.

Reversing of drive nay also be achieved by altering the phase coupling of the magnetic field of the motor and the alternating current supplied from the homopolar generator, by 180 . Similarly braking of the driven component may be achieved by reversing the phase coupling of the magnetic field of the motor and the alternating current supplied by the homopolar generator.

Transrission systems in accordance with the present Invention would be suitable for use with whee:e vehicles.

The system may include one or more motors, each arranged to drive a pair of wheels on an axle, through a conventional differential arrangement. However, preferably the wheels on one or more axles of the vehicle will be driven directly by individual motors, the speed of each wheel being controlled as appropriate, by suitable control logic.

An embodiment of the invention is now described, by way of example only, with reference to the accompanying drawling which illustrates in axial cross section, a homopolar generator/motor formed in accordance with the present invention.

The homopolar generator/motor illustrated in the accompanyinc drawing includes a rotor 10 having a haft 11 mounted for rotation in suitable bearings (not shown). An annular a.rlature 12 i::ade of ferromagnetic material is provided oil shaft 11. Sleeve 13 made of a material of good electrical conductivity, for example copper, is provided about the outer periphery of the armature 12. Flange portions 14 an 15 are provided at either end of sleeve 13 and extend part way along the radial faces of the armature 12.

The armature 12 is mounted to rotate within a stator which is defined by a pair of ferromagnetic plates 16 and 17 an: an annular ferromagnetic core 18. A pair of helically sound annular field coils 19 and 20 are provided, one recessed in each of the end plates 16 and 17, adjacent the inner periphery of the annular core 18.

The field coils 19 and 20 are adapted to be connected to an alternating current supply, so that they will produce an alternating magnetic field as indicatea in broken ine. A flux path is provided by tulle end plates 16 and 17, annular core 18 ano armature i2, so that the field passing through the sleeve 13 will be substantially radial.

A primary loop, in the form of a sleeve 21 of material or good electrical conductivity,, is provided about the outer periphery of annular core 18 and has flange portions 22 ano 23 which extend inwardly along the radial edges of core 18. The flange portions 22 and 23 also overlap radially, but are spaced axially fro, the flanges 14 and 15 of sleeve 13. Brushes 24 and 25 interconnect the overlapping annular portions of flanges 14 and 22 and 15 and 23 respectively, so as to connect sleeve 21 across sleeve 13.

The brushes 24 and 25 may be in the form of carbon rings which are spring loaded away from flanges 22 and 23 and into engagement with flanges 14 and 15. Preferably however the brushes 24 and 25 will be in the form of liquid metal contacts. One way of achieving this would be to mou- t the generator/motor so that the rotor 10 rotates about a vertical axis. Annular grooves may then be provide in the lower of the flanges 14 and 22 and 15 and 23 which are partially filled with a conductive liquid metal.

Formations on the upper of the flanges 14 and 22 and 15 and 23 may then extend into the annular grooves and into contact with the liquid metal, thereby permitting rotation of flanges 14 ano 15 while naintaining electrical connection thereof with flanges 22 and 23 respectively.

A secondary multi-wound coil 26 is wound toroidally about the core 18 underlying and electrically insulated from the sleeve 21.

when operating as a generator, the rotor 10 is drivingly connected to a prime over, for example an internal combustion engine of a motor vehicle. The alternating supply for th field coils 19 and 20 may be provided by an AC generator which is also driven by the prime mover, although if the prime mover is a fixed installation, the mains supply may be used for this purpose. By rotating te conductive sleeve 13 in the alternating magnetic field produced by the field coils 19, 20, a low voltage extremely high current, alternating current, is generated.

Typically, such a generator would have an output of iron 40 to 80 KW, providing 80000 to 160000 amps at 0.5 voits. The frequency, which is decided by the frequency of the current energising the field coils 19 and 20, may be from 20 to 2000 Hz.

The current generated in the conductive sleeve 13 then passes via the brushes 24 and 25 into the primary loop formed by sleeve 21 arid is transformed into a relatively high voltage low current, alternating current, typically 40 to 4O0 amps at 200 to Ec.O volts, in the secondary winding 20. This transformed current may then be conoucted using conventional cables, to a homopolar rotor of similar construction.

When opersting as a motor, the rotor 10 is erivingly connected to a driven component, for example the wheels of motor vehicle. The alternating current supplied to the field coils 19 and 20 may be the same as that used for the generator, but alternatively it may be tapped off the transformed supply delivered from the generator. Suitable control means is provided to ensure that the supply to the field coils 19 and 20 is maintained in appropriate phase with the supply trot the homopolar generator.The supply fro the homopolar generator is feo to the secondary winding 26 of the rotor, so that it is transformed back into an extremely high current low voltage alternating current in the primary loop formec by sleeve 21. The current in sleeve 21 is then fed into sleeve 13 via brushes 24 and 25 and tis alternating current in sleeve 13 in the presence of the alternating magnetic field produced by field coils 19 and 20, will cause the rotor 10 to rotate.

Various modifications nay be made without departing from the invention. For example while in the above embodiments, the current used to drive the hornopolar motor is produced by a homopolar generator of similar construction, a suitable current supply, that is typically 40 to 400 amps at 200 to 600 volts fror any source may be used.

Similarly, the transformed current provided by the homopolar generator may be used to power other form~ of notor or other crevices.

Instead of using a sleeve 13 to provide a conductive portion on the outer periphery of the armature 12, the armature itself may be made of soft iron which is a sufficiently good conductor of electricity.

Claims

1. A homopolar generator or homopolar motor comprising a rotor having an armature made of ferromagnetic naterial, at least the outer circumferential portion of the armature being of good electrical conductivity, said rotor being surrounded by a ferromagnetic stator, field coils being provided by on the stator, said field ccils being adepted te be connected to an alternating current supply ane being arranged to provide an alternating magnetic field which is substentially radial across said outer circumferentiel portion of the armature; said stator including an annular ferromagnetic core, a primery conductive loop being provided on the ferromagnetic core, said primary loop being connected by means of brushes at either eno to axially spaced positions on said outer circumferential portion of the armature, and a secondary winding being provided on the ferromagnetic core.

2. A homopolar generator or homopolar motor according to claim 1 in which the armature has a sleeve made rf conductive material mounted about its outer periphery.

3. A homopolar generator or homopolar motor according to clain 2 in which the sleeve has flange portions which extena towards to axis ot the rotor along the radial faces of the armature.

4. A homopolar generator or homopolar motor accoroin to any one of claims 1 to 3 in which te stator comprises a pair of axially spaced ferromagnetic end plates separated by said annular ferromagnetic core.

5. A homopolar generator or homopolar motor according to claim 4 in which two field coils of helically wound annular configuration are each located in a recces ir. one oi the end plates, said recesses being adjacent the inner periphery of the annular core.

6. A homopolar generator or homopoler motcr according to any one of the preceeding claims in which the primary conductive loop comprises a sleeve made of conductive material, said sleeve being mounted about the outer periphery of the annular ferromagnetic core, flange portions at either end of said sleeve extend inwardly along the radial edges of the core and overlap radially out are spaced axially from the outer portion of the armature.

7. A homopolar generator or homopolar motor according to claim 6 in which annular brushes provide contact between the flanges of the sleeve forming the primary loop and the opposed faces of the electrically conductive outer portion of the armature.

8. A homopolar generator or homopola motor according to any one of claims 1 to 7 in which the brushes are in the form of liquid metal contacts.

9. A homopolar generator cr homopolar motor according to any one of claims 1 to 7 in which annular carbon brushes provide contact between the primary loop and the conductive outer portion of the armatore.

10. A homopolar generator o homopolar motor substantially as descrited herein with reference te. and as shown in the accompanying drawing.

11. A transr-ission system including; a homopolar generator as claimed in any one of claims 1 to 10, said generator being drivingly connected to a prime mover; at least one honopolar motor as claimed in any one of claims 1 to 10, said motor being drivingly connected to a driven component, the secondary winding of the generator being connected to the secondary winding of the motor; and a secondary source of alternating current which is connected to field coils of the homopolar generator.

12. A transmission system according to clain 11 in which the fiela coils of the or each honopolar motor are connected to the secondary source of alternatinq current.

13. A transmission system according to claim ll wjiich current is tapped off the transformed current supply fron the homopolar generator to energise the field coils cf the or each motor.

14. A transmission system according to any one of claims li to 13 in which means is l provided to maintain appropriate phase coupling between the current supplied to the or each motor from the horlopolâ. generator and the current supplied to the field coils of the or each motor.

15. p transmission system according to any one of claime 11 to 14 in which means is provided to comptrol the speed of the prime mover to provide most efficient operation for tie power output required.

16. A transmission systen accoiding to any one of clains 11 to 15 in which the speed of the driven component is controlled by variation of the current energising the field coils.

17. A transmission system according to any one of claims 11 to 15 in .:hich the speed of the driven component is controlled by variation of the phase coupling between the current supplied from the horopolar generator and t};e current used to energise the field coils.

18. A transmission systen according to any one of clains 11 to 17 in which neans is provided to control the phase coupling between the current supplied by the homopolar generator and the current energising the field coils of the or each motor in order to provide breaking and/or reversal of drive.

19. A motor vehicle having a transmission system as claimed in any one of claims 11 to 18, the homopolar generator being drivingly connected to the engine of the vehicle and at least one homopolar motor being orivingly connected to wheel of the vehicle.

20. A vehicle according to claim 19 in which the wheels on one or nore axles of the vehicle are driven directly by individual homopolar motors.