EP0076282A1

EP0076282A1 - Dynamo-electric machine

Info

Publication number: EP0076282A1
Application number: EP19820900978
Authority: EP
Inventors: Vivian Geoffrey Endean
Original assignee: University of Durham
Current assignee: University of Durham
Priority date: 1981-04-06
Filing date: 1982-04-02
Publication date: 1983-04-13
Also published as: WO1982003506A1; GB2116780B; GB2116780A

Abstract

Une machine dynamo-electrique consiste en une machine a courant continu avec deux rotors enroules. L'un (1) des rotors est pourvu d'un arbre d'entree (12) et l'autre est pourvu d'un arbre de sortie. Les rotors sont situes a proximite l'un de l'autre et dans un circuit magnetique commun forme par un systeme d'enroulements de champ (3) et des aimants. Les deux enroulements des rotors et les enroulements de champ sont connectes electriquement entre eux par l'intermediaire de dispositifs de connexion electrique dont l'un (4) est situe sur l'arbre d'entree (12) et l'autre est situe sur l'arbre de sortie. Ces dispositifs de connexion electrique sont associes a des balais (5) qui peuvent etre mobiles ou reglables et qui s'appuient sur les dispositifs de connexion electrique. Associe a la machine, un circuit electrique permet a un courant genere par l'action de l'un (1) des rotors par rapport au champs d'exciter l'autre rotor qui, lui, agit comme un moteur en association au champs.A dynamo-electric machine consists of a DC machine with two wound rotors. One (1) of the rotors is provided with an input shaft (12) and the other is provided with an output shaft. The rotors are located close to each other and in a common magnetic circuit formed by a system of field windings (3) and magnets. The two rotor windings and the field windings are electrically connected to each other by means of electrical connection devices, one of which (4) is located on the input shaft (12) and the other is located on the output shaft. These electrical connection devices are associated with brushes (5) which can be mobile or adjustable and which are based on the electrical connection devices. Associated with the machine, an electric circuit allows a current generated by the action of one (1) of the rotors relative to the fields to excite the other rotor which, him, acts as a motor in association with the fields.

Description

"DYNAMO-ELECTRIC MACHINE"

This invention relates to a dynamo-electric machine which at least in a preferred form can provide a variable power coupling.

Hitherto, the variable transfer of power between the rotary shaft of a prime mover and a rotary output shaft has been achieved with the aid of mechanical gear boxes or, for example, infinitely variable belt drives. It is known to provide a torque converter or variable electrical gear box in the form of a homopolar d.c. machine in which two rotors are mounted back-to-back in one housing with a common centre slip-ring, connection. However, such a machine suffers from the known disadvantages of homopolar machines and in a practical form requires liquid metal slip-rings.

The present invention is a dynamo-electric machine which may be used to transfer power between an input rotor shaft and an output rotor shaft and provide a variable angular velocity ratio or torque ratio. According to one aspect of the invention a dynamo-electric machine comprises two wound rotors disposed adjacent each other, means for providing a common field for the two rotors, means for connecting electrically the rotors' windings and means for adjusting the coupling of current to or from at least one of the rotary windings relative to the field so as to vary the exchange of power between the rotors. In its normal form, the rotors are termed the input rotor and the output rotor and fitted with an input shaft and an output shaft respectively.

The said means for adjusting may comprise means for shifting the field but in preferred embodiments of the invention at least one of the rotors may be provided with a commutator associated with brushes which can be rotated.

Preferably the rotors and .the field are connected electrically by way of an electrical circuit by means of which current generated by the action of one rotor and the field provides energisation of the field and the other rotor. The electrical circuit may include means for controlling the direction of current flow in a winding for the production of the field and the rotor windings or for various other purposes. According to another aspect of the invention a dynamo electric heteropolar machine comprises two wound rotors disposed adjacent each other, a system providing a common magnetic circuit in which the rotors rotate, terminal connections for the two rotors and means for adjusting at least one of the terminal connections. The said terminal connections may comprise a commutator having brush gear which is rotatable relative to the axis of the respective rotor.

There follows a more detailed description, by way of example, of the present invention, with reference to the accompanying drawings, in which:-

Figures 1 and 2 illustrate in side section and partial end elevation respectively part of a dynamoelectric machine according to the invention; and Figure 3 illustrates an electrical circuit including the dynamo-electric machine.

In its preferred form a dynamo-electric machine, which may be termed "Engudyne", according to the present invention comprises the heteropolar direct current machine with two wound rotors. One of the rotors is termed the input rotor and the other is termed the output rotor. The rotors are located near each other and in a common magnetic circuit provided by a system of field windings and magnets. The two rotor windings and the field windings are electrically connected to each other through electrical connection devices, of which one is located on the shaft of the input rotor and the other is located on the shaft of the output rotor. These electrical connection devices are associated with brushes which may be movable or adjustable and which bear on the electrical connection devices. Associated with the machine is an electrical circuit which enables current generated by the action of one of the rotors relative to the field to provide energisation for the other rotor, which acts as a motor in conjunction with the field. The result of rotating the brushes for the input rotor is that the currents in the input rotor are moved relative to the common magnetic field. The torque developed is proportional to the current in the rotor and to the common magnetic field strength, but the constant of proportionality is altered by rotating the brushes. At the same time the emf generated in the rotor is proportional to the speed of the rotor and to the common magnetic field, but. again the constant of proportionality is altered by rotating the brushes. If the brushes of both the rotors are aligned, the rotors, in the absence of losses, rotate at the same speed, develop equal and opposite torques, and have the same terminal voltage. When the sets of brushes are rotated out of alignment, the input rotor experiences the same magnetic field as the output rotor but reduced by a constant factor determined by the brush angle. This rotor therefore develops less torque (by this factor) so that in the absence of losses, it must go faster than the output rotor. The product of torque and speed must be equal for hoth rotors, neglecting losses. Thus the brush rotation controls speed ratio or torque ratio without constraining the total power transfer.

Although it may be feasible to construct the machine as a homopolar machine, it is very preferable for the machine to be heteropolar. In the specific embodiment which will be described later, the machine is a d.c. machine which has commutators for both rotors. However, it may be feasible to use other means of connecting electrical power to and from the rotors, such as for example slip-rings. Moreover, static commutating circuits, including thyristors, may be used to achieve the same effect as the rotation of brushes relative to a commutator ring. It is feasible to achieve a similar effect to that of shifting the brush gear by the rotation of the field system but in practice this expedient is much less convenient.

It may furthermore be feasible to constitute the machine as an a.c. generator and motor. The a.c. generated by the input rotor would be full-wave rectified to d.c. The d.c. would supply the field windings. A thyristor inversion circuit would then supply a.c. to the output rotor. The frequency of the output a.c. would be controlled electronically in the thyristor circuit and this would effectively perform the same function as rotating the brushes in the d.c. version.

Although a specific embodiment of the electrical circuit will be described hereinafter, in general the circuit may incorporate a system of diodes in a bridge network, switches and other control devices. These devices may be used to control the direction of current flow in the field windings and the rotor windings and for various other purposes. Thus the direction of rotation of an output rotor may be reversed with respect to the rotation of the input rotor. The direction of power flow can be made one way or both ways independently of the control of velocity ratio and torque ratio. The input section of the machine may be connected to an external electrical power source and used as a starter motor for the prime mover. The output section of the machine can be connected to an external electrical power source and be used as an alternative drive motor. The machine can be used to charge an external electrical power source using pcwer delivered either to the shaft of the input rotor or to the shaft of the output rotor. The machine might also be used as a straightforward electrical, brake, excess energy being either dumped in an external load or absorbed in the machine itself. Overload conditions can be catered for and the currents and voltages in the machine can be monitored and used in the manual or automatic control of the terminal connections which control the velocity ratio and the torque ratio and possibly in the control of the prime mover and the load as well.

The machine may be used, for example in a motor vehicle to replace at least the gear box thereof.

Figure 1 illustrates one half of a preferred embodiment of the new machine. The second half is similar and is arranged "back-to-back" with the illustrated half.

The principal parts of the illustrated input half of the machine comprise a rotor 1, which in this embodiment of the invention is the input rotor, a plurality of pole pieces 2, field windings 3 disposed on the pole pieces, a commutator ring 4 disposed on the shaft 12 of the rotor 1, terminal brush gear 5, bearing on the commutator ring, a magnetic steel end plate 6 by means of which the rotor and the field system are supported, a bearing 7a supported by the end plate 6 and itself supporting the rotor l for rotation, a cover or cage 8 which. extends from the end elate. 6 to i ts counterpart in the other half and a rotor winding 9, comprising a multiple turn winding of which, the coil sides 11 lie flat on a disc 10 of electrically insulating material. The rotor winding is preferably made of wires or alternatively strips which are located, as mentioned, partially in the slots of the rotor and partially in coil configurations at the inner and outer parts of the rotor. The wires or strips are composed of, for example, copper or aluminium.

It will be noted that the coil sides 11 are arranged radially en the disc 10 in the region which passes adjacent the pole pieces 2 and are coiled at the periphery of the disc 10.

The shaft 12 of the rotor 1 has a radial flance 13 which Supports the disc 10. The disc has a central recess 14 defined by the axial flange 15a and the base 15 which is secured to the flange 13. The inner ends 16 of the coils of the winding 9 extend into the recess 14, which is closed by a cap 15c. Wires 17 which are composed of, for example, copper or aluminium extend from the coil ends 16 through bores, extending axially, in the shaft 12 to the commutator 4. The flange 15a has radial slots which accommodate the radial protrusions constituted by the inner ends 16 of the rotor winding, these ends being insulated and bended in the radial slats. Thrust bearings 7b and 7c are provided for the part 12. For each of the pole pieces the end plats 6 has a cylindrical hole 20 of which the axis is parallel to the axis of the rotor 1 and is located approximately three quarters of the mean radius of the end plate from that axis. The diameter of the hole is approximately one third of the radius of the end plate. A solid magnetic steel cylindrical bar 21 is placed in the hole and is attached to the end plate so that one end 22 of the bar is flush with the outer face of the end plate whereas the other end of the bar extends towards the rotor from the end plate. The magnetic steel pole piece 2 is in the form of a flat plate of approximately hollow circular quadrant shape and is attached to the bar so that when it is in position there is a small clearance 23 between the pole piece and the rotor 1. Three more bars and respective pole pieces are fitted to the end plate 6 in similar fashion, the four bars and their pole pieces being equally spaced about the common axis. The bars and pole pieces which are fitted to the end plate of the other half of the machine are disposed in similar fashion and such that the bars and pole pieces in the input and output halves of the machine lie symmetrically opposite each other.

Eight circular copper coils (3) are placed on the eight bars to constitute the field windings. The pole pieces, the air gaps between them, the bars and the end plates together constitute a common magnetic circuit for the two rotors.

The brush gear 5 preferably comprises four brushes which spring fitted in a rotatable housing. The brush housing is rotatably located on the input end plate 6 such that the brushes bear on the respective commutator at locations 90º apart. A linkage is affixed to the brush housing to facilitate its rotation. A similar brush arrangement is provided in the output half of the machine. Preferably the free ends of the input and output shafts are fitted with flexible couplings. The complete assembly may be fitted with shoes so that it can be affixed to a test bed such that the common axis of the input rotor 1, and the output rotor (not shown) is horizontal. Figure 3 illustrates one example of a circuit diagram of the machine as connected for operation. The winding 9 of the input half generates a terminal voltage. One terminal is connected by way of a fuse 30 and an on/off switch 31 to one terminal of a double pole contactor 32 by means of which current generated by the winding 9 may be caused to flow in either a forward or reverse direction through the winding 9a of the output half of the machineThe terminals 33 and 34 of this winding 9a are shown adjacent the contactor for convenience. The current path subsequent to the winding 9a extends through a line 35 to a high-current diode bridge 36 and thence through the field windings 3, the diode bridge 36 ensuring that the current in the field windings 3 is always in the same direction, and ultimately to an earthed line 37 which Is connected to the other terminal of the input rotor winding 9. Included in this current path is a low resistance shunt 38 by means of which a voltage representing the current flowing through the windings 9 and 9a and the field 3 may be monitored. Other monitoring terminals are provided for the terminal voltage of the winding 9 and the terminal voltage of the winding 9a.

Between the contactor 32 and the diode bridge 36 is a further switch 39 by means of which the operation of the machine may be changed from "coast" to "power braking". When the coast/power braking switch 39 is open, one half of the diode bridge is disconnected from the output rotor winding so that current can only flow one way In the output rotor winding. The direction in which the current can flow is such that torque can be developed on the output rotor only to deliver power to the load. Figure 3 illustrates diagrammatically the facility of rotating, either manually or automatically the brush gear for the winding 9. The voltage developed across the resistor 38 may be used for automatic control, being amplified as necessary and used in the control of a motor which rotates the brush gear for the winding 9. In practice the maximum current should be limited and the voltage developed across the resistor 38 may be used to override the control of the speed ratio if this be such as to cause the flow of excessive current.

Claims

CLAIMS ;

1, A dynamo-electric machine characterised by the combination of two wound rotors (1) disposed adjacent to each other, means for providing a common field for the two rotors, means for connecting electrically the rotors' windings (9) (9a) and means for adjusting the coupling of current to or from at least one of the rotary windings (9) .(9a) relative to the field so as to vary the exchange of power between the rotors (1).

2. A dynamo-electric machine according to Claim 1 wherein the means for adjusting comprises means for shifting the field.

3. A dynamo-electric machine according to Claim 1 wherein at least one of the rotors (1) is provided with a commutator (4) which is associated with brushes (5) and which can be rotated.

4. A dynamo-electric machine according to any one of Claims 1, 2 or 3 wherein the rotors (1) and the field are connected electrically by way of an electric circuit by means of which current generated by the action of lone rotor (1) and the field provides energization of the field and the other rotor (1).

5. A dynamo-electric machine according to Claim 4 wherein the electric circuit comprises means (32, 36, 39) for controlling the direction of current flow in the windings (3, 9, 9a).

6. A dynamo-electric heteropolar machine comprising two wound rotors (1) disposed adjacent each other, characterized by a system providing a common magnetic circuit in which the rotors (1) rotate, terminal connections for the two rotors and means for adjusting at least one of the terminal connections.

7. A dynamo-electric heteropolar machine according to Claim 6 wherein the terminal connections comprise a commutator (4) having brush gear (5) which is rotatable relative to the axis of the respective rotor (1).