US2278489A - Magneto-electric machine - Google Patents

Magneto-electric machine Download PDF

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Publication number
US2278489A
US2278489A US141669A US14166937A US2278489A US 2278489 A US2278489 A US 2278489A US 141669 A US141669 A US 141669A US 14166937 A US14166937 A US 14166937A US 2278489 A US2278489 A US 2278489A
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Prior art keywords
magnet
armature
polar
flux
speed
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Expired - Lifetime
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US141669A
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English (en)
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Rawlings George William
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Individual
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Individual
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K21/00—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets
    • H02K21/12—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with stationary armatures and rotating magnets
    • H02K21/22—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with stationary armatures and rotating magnets with magnets rotating around the armatures, e.g. flywheel magnetos
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K21/00—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets
    • H02K21/26—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with rotating armatures and stationary magnets
    • H02K21/28—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with rotating armatures and stationary magnets with armatures rotating within the magnets
    • H02K21/30—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with rotating armatures and stationary magnets with armatures rotating within the magnets having annular armature cores with salient poles

Definitions

  • This invention relates to magneto-electric generators, that is to say, dynamos incorporating a permanent magnet element, and more particularly to such machines of the kind comprising a one piece multi-polar permanent magnet field magnet encircling a multi-polar armature, that is to say, such having at least 4 magnetic poles.
  • the primary object of the invention is to provide a simple means of obtaining load voltage/speed regulation combined with high specific output in a small dynamo suitable for use in the electric lighting system of a cycle or motor cycle.
  • load voltage/speed is used herein to mean the relation between the speed and the voltage generated under load, as compared with the relation on open circuit, that is to say, the relation as may be represented by a graph plotting voltage readings against speed.
  • a dynamo possessing this desirable characteristic the rated output is reached at a comparatively low speed, and is maintained substantially constant thereafter despite even a large increase in speed.
  • a dynamo of 6 volts 6 watts rating would begin to light a 6 volt 6 watt bulb at 3 cycle miles per hour, and would reach its 'rated output at 11 or 12 cycle miles per hour, and yet would not unduly overload the bulb at 30 cycle miles per hour.
  • the optimum lengthsection ratio for the field magnet may be substantially retained while bringing the contour of the inner polar portions of the magnets close to the armature tunnel and thereby more effectively placing the magnet in the path of the armature reaction flux.
  • the expression negative susceptibility is used to indicate the inherent opposition of already magnetised metal to the entrance and passage of an opposite magnetic fiux.
  • a magneto-electric machine of the kind having an armature encircled by a one piece ring permanent magnet with at least four magnetic poles of alternate polarity or a magnet therefor is characterised in that the inner contour of the magnet between such poles is either an uninterrupted cylindrical bore forming the armature tunnel or an interrupted bore comprising alternate polar projections and interpolar spaces, which spaces are collectiveiy less than 25% of the volume of the metal of the magnet.
  • Fig. 1 shows diagrammatically the field magnet and armature of a dynamo
  • Fig. 2 is a side elevation of the field magnet shown in Fig. 1.
  • Figs. 3 and 4 show forms of continuous ring magnets having polar projections and interpolar spaces
  • Figs. 5, 6 and 7 are graphs showing the characteristics of the dynamos employing respective- 1y the field magnet shown in Figs. 1, 3 and 4.
  • Figs. 8 and 9 show another form of field magnet particularly suitable for a slow speed dynamo.
  • Fig. 10 shows a flux diagram illustrating a means of determining the contour of an interpolar space.
  • the characteristic curves shown in Figs. 5. 6 and 7 indicate still further the method whereby voltage regulation is eilected by determining the inner contour of the magnet between the poles.
  • US and A/S indicate voltage-speed curve and current-speed curve re spectiveiy. These curves show the characteristics oi a typical dynamo when fitted alternatively with the magnets shown in Figs. 1, 3 and 4.
  • These three magnets are designed to be made from magnet material 01 high coercivity such as the nickel aluminium alloys having a coercive force of 500 Gilberts per centimeter.
  • the optimum dimensional relation for such metal is about 3/1, therefore the magnet is designed to have one unit in section and I2 units in mean circular length.
  • the length of each magnet compared with its section is 3/1, so that the metal is used under optimum conditions, i. e., to give the maximum, magnetic strength/weight ratio. This ratio is substantially maintained in all the examples herein described.
  • the magnet shown a in Fig. 1 has an uninterrupted circular bore a, that is to say, with no defined polar projections. but it is magnetised to have four magnetic poles as indicated.
  • the magnet shown in Fig. 3. is formed with arched inter polar spaces d rising to 1*.” beyond the armature tunnel, whilst the magnet e shown in Fig. 4, has a still more defined arched contour between the polar projections. and this is the preferred form.
  • Each field magnet was permanently magnetised, prior to test, in position in the machine by passing momentarily through the armature windings a current of 40 amperes.
  • the armature reaction is less eifective as a means of load voltage/speed regulation, and accordingly within the limits of a given machine the load voltage/speed characteristic under a given load can be determined as required by determining the form or the inter polar contour of the encircling permanent magnet.
  • the field magnet shown in Figs. 8 and 9 illustrates a practical form of a magnet for a slow speed multi-polar dynamo embodying the load voltage/speed determination feature of the invention.
  • the spaces 01 the permanent rings of Figs. 3, 4 and 8 are so formed that the depth of the rings as measured in a radial direction at the spaces is considerably less than the depth of the rings as measured in a radial direction at the polar projections.
  • the depth of the rings at the spaces is about 66 per cent of the depth of the rings at the polar projections and in Fig. 3 the depth oi the ring at the spaces is about per cent of the depth of the ring at the polar pro- Jections.
  • Fig. 10 shows a theoretical iiux diagram of armature reaction flux.
  • the lines of magnetic fiux illustrated follow the recognised theory of crossing equi-potential planes at right angles, assuming that they remain in the same medium, such as air.
  • B represents the flux path commencing from points half way between the half pole centres and the pole tips and subtending an angle of about 56 degrees at the center and is the preferred limit of shaping, beyond which effective voltage/speed control is lost.
  • the shaded portion between the armature tunnel and this line B represents the area within which the inter polar shape effects the loadvoltage/speed characteristic, according to the present invention, it being assumed in this example that the pole width is equal to the width of the inter polar space.
  • the line C represents a suitable inter polar shape for the field magnet, such line lying within the shaded area. As can be seen, the volume of the interpolar spaces represented by the shaded area is lessthan 25% of the volume of the metal of the magnet.
  • the armature lamination form shown is a compromise as regards length of pole tip;
  • the length mustbe restricted to facilitate winding by machine.
  • the armature does not actually bridge the pole tips but the material for the magnet is of such high coercivity that there is no appreciable loss from open-circuiting to this extent.
  • a dynamo which comprises a continuous ring permanent magnet having at least four magnetic poles of altemate' polarity, an armature having the same number of poles as the ring magnet, the inner contour of the ring magnet comprising alternate polar projections and" arched interpolar spaces, the interpolar contour of each interpolar space being substantially along an arched line connecting the inner extremities of the polar projections, the formation of the magnet between the polar projections conforming to the natural path of the armature reaction flux in air, so that the reaction flux effectively restricts the flux of the permanent magnet, the dynamo having the characteristics of load voltage/speed regulation combined with high specific output.
  • a dynamo which comprises a continuous ring permanent magnet having at least four magnetic poles of alternate polarity, the inner contour of the ring magnet comprising alternate polar projections and interpolar spaces, the contour of each interpolar space being substantially coincident with an arched line connecting the inner extremities of the adjacent polar projections and conforming generally to an armature reaction flux path; in air connecting the same extremities, said armature reaction flux path being located between the armature poles in air when the ring magnet is removed.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Permanent Field Magnets Of Synchronous Machinery (AREA)
  • Dc Machiner (AREA)
US141669A 1936-05-12 1937-05-10 Magneto-electric machine Expired - Lifetime US2278489A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB2278489X 1936-05-12

Publications (1)

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US2278489A true US2278489A (en) 1942-04-07

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US141669A Expired - Lifetime US2278489A (en) 1936-05-12 1937-05-10 Magneto-electric machine

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US (1) US2278489A (enrdf_load_stackoverflow)
BE (1) BE421528A (enrdf_load_stackoverflow)
NL (1) NL48570C (enrdf_load_stackoverflow)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2717321A (en) * 1951-08-20 1955-09-06 Harry C Stearns Dynamotor
US2894156A (en) * 1957-09-12 1959-07-07 Minitone Inc Miniature motor
US3064150A (en) * 1957-05-23 1962-11-13 Emi Ltd Electric motors
US3324841A (en) * 1963-07-24 1967-06-13 Curtiss Wright Corp High frequency ignition system for aircraft engines and the like
US4453097A (en) * 1982-09-01 1984-06-05 Powertron Division Of Contraves Goerz Corp. Permanent magnet DC motor with magnets recessed into motor frame
US20080030095A1 (en) * 2006-08-04 2008-02-07 Satoshi Iizuka Small-sized motor having ring-shaped field magnet
US20080278015A1 (en) * 2003-10-31 2008-11-13 Karl Reisinger Actuator Having An Electric Actuating Motor And Controllable Friction Clutch Having Such An Actuator

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2717321A (en) * 1951-08-20 1955-09-06 Harry C Stearns Dynamotor
US3064150A (en) * 1957-05-23 1962-11-13 Emi Ltd Electric motors
US2894156A (en) * 1957-09-12 1959-07-07 Minitone Inc Miniature motor
US3324841A (en) * 1963-07-24 1967-06-13 Curtiss Wright Corp High frequency ignition system for aircraft engines and the like
US4453097A (en) * 1982-09-01 1984-06-05 Powertron Division Of Contraves Goerz Corp. Permanent magnet DC motor with magnets recessed into motor frame
US20080278015A1 (en) * 2003-10-31 2008-11-13 Karl Reisinger Actuator Having An Electric Actuating Motor And Controllable Friction Clutch Having Such An Actuator
US20080030095A1 (en) * 2006-08-04 2008-02-07 Satoshi Iizuka Small-sized motor having ring-shaped field magnet
US7732963B2 (en) * 2006-08-04 2010-06-08 Mabuchi Motor Co., Ltd. Small-sized motor having ring-shaped field magnet

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NL48570C (enrdf_load_stackoverflow)
BE421528A (enrdf_load_stackoverflow)

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