GB2139012A - Electromagnetic machines - Google Patents

Abstract

An electromagnetic machine for use as a D.C. motor and/or dynamo and/or an A.C. synchronous generator has windings 25 disposed on both the sides and the ends of the armature with magnets 10, 12 at the sides and ends of the armature confronting the respective windings 25. This produces greater power output and so can be used in for example vehicles for producing energy which can be stored and used later. Alternatively, the machines can be made less bulky. <IMAGE>

Description

SPECIFICATION Electromagnetic machines This invention relates to electromagnetic machines, including electromagnetic generators and motors.

In a conventional D. C. electromagnetic machine, a number of slots for accommodating windings are provided on the surface of a cylindrical armature.

Upon the stationary armature winding energized with electric current being acted on by the stator magnetic fields, the armature will rotate. Alternatively, upon the moving armature winding cutting the stator magnetic field, the machine will generate electrical energy. However, the magnetic cutting phenomenon between the armature conductors and the stator magnetic field is limited by the available winding on the armature and the stator magnetic poles.

Referring to Figure 1, there is shown a conventional two-pole D. C. motor, in which if the current is flowing in a direction as illustrated from Fleming's lefthand motor rule the armature will rotate counterclockwise as a result of the force being applied to the armature winding. Such force is due to interaction between the winding carrying current and the magnetic poles. The direction of rotation of the armature, in which the polarity of the armature field is symbolized with two dotted characters in Figure 1, may also be found by the attracting and repelling effects between the stator and the rotor. Although in a conventional D. C. motor, the power output may be increased by increasing the number of magnets or the number of current-carrying windings the dimensions and weight of the motor will then be increased.

This also similarly takes place in a conventional D. C.

generator in order to obtain a higher power output.

An object of the present invention is to rovide an electromagnetic machine in which the output power is increased.

According to this invention, we propose an electromagnetic machine comprising an armature having a plurality of longitudinal, first slots along its length and a plurality of second slots at each end, a plurality of windings, for carrying current, disposed in the first and second slots, first means disposed adjacent the sides of the armature for exerting magnetic forces and second means disposed adjacent the ends of the armature for exerting magnetic forces so as to confront the windings and of such polarity that substantial components of the respective resulting forces are in the same direction.

Embodiments of the invention are described by way of example with reference to the drawings, in which: Figure l is a schematic diagram of a conventional two-pole D. C. motor in which the polarity of the armature field is labelled with two dotted characters, N,S; Figure 2 is a schematic, exploded view of first embodiment of the present invention, in which two dual U-shaped armature coils are illustrated; Figure 3 is a sectional view taken along section line A - A in Figure 2 looking in the direction of the arrows, wherein the actual positions of the magnetic poles are also shown; Figure 4 is a schematic diagram showing the position of a dual U-shaped coil on the armature core; Figure 5 is a schematic diaram showing a single turn of a dual U-shaped coil exposed to magnetic fields;; Figure 6 is a schematic, sectional view of further embodiment of the present invention, in which the armature core is mounted with three sets of dual U-shaped armature windings.

Referring to Figure 2, there is shown an exploded view of an embodiment of the present invention, having a plurality of armature slots 20, formed between a plurality of armature teeth 21 in the form of silicon steel laminae of the armature core 2 and four stator magnetic poles 10 made of permanent magnets surrounding the sides of the armature.

Further armature teeth 23 in the form of silicon steel laminae, are disposed at each end of the armature core 2. The outer laminae 23 are exactly flush with the original armature teeth 21 so as to form a plurality of slots transverse to the slots along the sides of the armature. The added armature teeth 23 are fixed to the original armature teeth 21 by two rivets 30 or, alternatively spot welding.

In the stator portion, four added stator magnetic poles 12 are furnished adjacent and confronting each end of the armature core 2 with alternate polarities as shown in Figure 2. The width of the added armature slots 24 covered by two opposite added stator magnetic poles 12 is at least the same as the width of the original armature slots 20 covered by the original stator magnetic poles 10 between the two added stator poles 12. Two of each of the four magnets of both types 10 and 12 havethe same polarity and the polarities of every first two magnets at opposite ends are the same as that of the second magnet therebetween and adjacent the side of the armature.

In the embodiment shown in Figure 2, two dual U-shaped armature coils 25 are shown and each is mounted in a longitudinal armature slot 20 to be covered by stator magnet pole portions 10 and four of the transverse armature slots 24 which communicate with the two longitudinal armature slots 20.

According to the aforementioned winding method, a D. C. electromagnetic machine may be manufactured by using a number of the dual U-shaped coils 25 arranged in conventional lap winding or wave winding method around the armature.

Referring to Figure 3, there is shown an enlarged longitudinal sectional view of the armature core 2 from line A -A in Figure 2 and the actual positions in use of the stator poles 10 and 12 are shown. Each dual U-shaped armature coil 25 confronts three stator magnetic poles 10 and 12 of the same polarity.

Consequently, upon the armature being rotated, each dual U-shaped armature coil 25 will cut the stator magnetic fields which act on the three external sides of each half of the armature core 2 in three directions. Thus, upon the armature coil 25 carrying a current, every conducting portion of the coil will be affected by three forces in the same direction generated by the three stator magnetic poles 10 and 12.

The gap between the stator and the rotor may range typically from 0.35 mm to 2 mm. To produce a power over 1OHP (7460 Watts), the stator magnetic poles 10 and 12 as shown in Figure 2 and 3 may be replaced with electromagnets (referring to Figure 6).

The thickness and length of the added armature teeth 23 may also be increased, if it is necessary to increase the length of the armature conductors, and to increase the windings in the added armature slots 24.

Referring to Figure 4, there is shown a dual U-shaped armature coil 25 for a multi-pole electromagnetic machine. Furthermore, the two U-shaped portions of the armature coil 25 may be bent slightly away from each other, i.e. an angle over 90" subtends between the U-shaped portions and the straight portions of the coil 25. The armature coil 25 is connected with two leads 251 similar to that of a conventional D. C. electromagnetic machine for connection to a commutator. Further, the armature core 2 as shown in Figure 2 may also be mounted with an A. C. three-phase winding composed of the dual U-shaped armature coils 25. In that case, the leads 251 are connected to a dynamo slip ring. Since the generation of a dynamic force is determined by the relative motion between the stator and the rotor, the three-phase winding in an A.C. synchronous electrodynamic machine may be either mounted on the stator or the rotor. Thus, upon the armature core 2 being mounted with a three-phase winding, an A.

C. generator may be obtained. Of course, the arrangements of the stator magnetic poles 10, 12 and the armature winding can also be interchanged.

Referring to Figure 5, there is shown a schematic diagram illustrating the relationship of position and magnetic field between the dual U-shaped armature conductor 25' and the stator poles 10 and 12, wherein the broken lines denote schematically the stator poles 10 and 12. Supposing the armature current la flowing in a direction as shown in Figure 5, the sections and a'b' of the dual U-shaped armature conductor 25' in the longitudinal slots will be acted on by the forces f1 and f2 as a result of the effect of the two adjacent poles 10, for section ab is located under an "S" pole and section a'b' is located under an "N" pole. The direction of the forces f1 and f2 may be determined with the Lefthand Rule.By the same token, since the sectionsac, a'c', bd and b'd' of the armature conductor 25' in the transverse slots are facing respectively the four added stator magnetic poles 12, they will be acted on respectively by the forces f3 to f6 in the same direction as that of the forces f1 and f2 so the forces are additive. Substantial components of the respecting resulting forces f3 to f6 must be in the same direction as f1 and f2 and must be greater than zero.

It is apparent that the torque generated with forces f, to f6 is much greater than that of a conventional motor in which only the sectionsab and a'b' are acted on. Furthermore, a D.C. motorforinstance according to the present invention can be smaller and lighter than a conventional D.C. motor.

According to the electromagnetic torque equation.

T = PZ/L. la, in which "" stands for the magnetic flux of each stator pole and "L" stands for the number of the parallel loop of the armature winding, the torque "T" can be increased by increasing the total number of the armature conductors "Z" or the number of the stator poles "P". In the conventional D.C. machine, the rectangular armature conductor has only two sides parallel to the rotor axle (referring to Figure 1) to be acted on by the magnetic fields of the stator, while the other two sides serve only as electric conductors. To increase the torque by increasing the number of armature conductors "Z" is all right, but part of the weight of the armature conductor increased has no use in increasing the torque; therefore, the usefulness of the armature conductors will be reduced.

In the present invention, a dual U-shaped armature winding is used for increasing the output torque of the machine.The reason is that only two out of eight sections of each dual U-shaped armature conductor 25' (i.e. sections, cc' and dd' shown in Figure 5) are useless in elevating the torque; the other six sections will be useful as a result of being acted on by the stator magnetic poles. If the same torque is needed, the present invention having the dual U-shaped armature conductor (i.e. "elongated") is able to reduce the size and the weight of a machine in comparision with the conventional electromagnetic machines.

As to increasing the torque by adding more stator poles "P", the added transverse stator magnetic poles 12 (as shown in Figure 2) in the present invention are used for providing the second and third magnetic fields to the dual U-shaped amarature winding. In that case, the ratio between the torque (AT) from increasing the magnetic poles and the weight (AW) added to the stator, i.e. AT/AW,in the present invention can at least be as favourable as for conventional electromagnetic machines.

Referring to Figure 6, there is shown a sectional view of another embodiment of the present invention, in which the stator poles 10' and 12' are electromagnets, and three sets of dual U-shaped armature windings are mounted on the armature core 2. In each armature slot, three layers of dual U-shaped armature coils 25 are mounted; in the three layers, the top layer and the middle layer are used respectively as a D.C. motor coil and a D.C.

generator coil, and the bottom layer is used as an A.C. synchronous generator coil. As shown in Figure 6, there are two commutators 4a and 4b and three slip rings 6, which are coupled respectively to the brushes 5a, 5b and Sc so as to enable the machine to simultaneously or separately provide the function of a D.C. motor, a D.C. generator, and an A.C. generator.

The embodiment shown in Figure 6 can be used in an electromotive automobile or an electromotive motorcycle, the two generators may, by means of the down-hill force of the vehicle during driving downhill, generate power to charge a storage battery through brushes 5b and Sc (the A.C. from brush Sc being rectified before charging into the battery).

Upon the vehicle driving uphill or bearing a considerable load, the power may, through the brushes 5a and 5b, be delievered to the two D.C. motors to drive the vehicle. Further, when using wind, heat, or solar energy to generate power, the present invention may directly provide A.C. power output for the A.C.

load without requiring an inverter as the conventional energy conversion device does to change the D.C.

output to A.C. power before applying the A.C. load.

Claims (7)

1. An electromagnetic machine comprising an armature having a plurality of longitudinal, first slots along its length and a plurality of second slots at each end, a purality of windings, for carrying current, disposed in the first and second slots, first means disposed adjacent the sides of the armature for exerting magnetic forces and second means disposed adjacent the ends of the armature for exerting magnetic forces so as to confront the windings and of such polarity that substantial components of the respective resulting forces are in the same direction.

2. A machine according to claim 1, wherein the second slots are substantially perpendicular to the first slots.

3. A machine according to claim 1, wherein the windings are in the form of two U-shaped portions the ends of which are joined together by straight portions and the U-shaped portions are disposed in the second slots and the straight portions in the first slots.

4. A machine according to claim 3, wherein the first and second slots are defined between laminae projecting from the ends of the armature.

5. A machine according to claim 3 or 4, wherein the polarities of every two first magnets at opposite ends of the armature are identical to that of the second magnet therebetween and adjacent the side of the armature.

6. A machine according to claim 3,4 or 5, wherein one or more furtherwindings are disposed over the windings whereby the machine may be employed as one or more of a direct current motor, a direct current dynamo or an alternating current synchronous generator.

7. An electromagnetic device constructed and arranged substantially as herein described with reference to any of Figures 2 to 6 of the drawings.