GB2043359A

GB2043359A - Alternating current machine arrangement

Info

Publication number: GB2043359A
Application number: GB8001618A
Authority: GB
Original assignee: Bendix Corp
Current assignee: Bendix Corp
Priority date: 1979-02-15
Filing date: 1980-01-17
Publication date: 1980-10-01
Also published as: DE3002527A1; FR2449356A1; IT1140538B; JPS561755A; IT8019807A0

Abstract

An alternating current machine arrangement comprises a pair of electromagnetic structures (4, 6) each provided with a stator (16, 18) and a rotor (24, 26) having polyphase windings (20, 28; 22, 30), with the rotor windings (28, 30) interconnected for reverse phase rotation, a constant frequency power source (41), a variable frequency converter (47), a prime mover (51), and an electric load (49), and which arrangement according to the connections and the coupling with the associated elements operates as a brushless alternating current rotational position transducer brushless alternating current torque transducer brushless alternating current synchronous motor (Fig. 3), or a brushless alternating current synchronous generator (Fig. 4). <IMAGE>

Description

SPECIFICATION Alternating current machine arrangement This invention relates generally to alternating current machines and, particularly, to an alternating current machine arrangement which functions as a brushless synchronous motor, a brushless synchronous generator, a brush less rotational position transducer, and a brush less torque transducer.

Modern aircraft engines, for example, are started using air turbine starters (motors) interfaced through an accessory gearbox pad. Compressed air is supplied to the starter through pneumatic valves and plumbing via an external compressed air source.

Once the engine is started, the air turbine starter is deenergized and remains inactive, although it continues to add weight to the engine and consumes valuable space.

During flight, electrical power is supplied to the aircraft via a constant frequency generating system including a variable speed, variable frequency generator interfaced to the aircraft engine through an additional accessory gearbox pad and a static frequency converter which transforms the variable frequency generator power to constant frequency aircraft system power. During conditions when the aircraft engines are shut down, such as when the craft is parked at a terminal, electrical power is supplied to the craft via a constant frequency external power supply, commonly known as a ground power cart or on-board auxiliary power unit.It is the object of the present invention to use a variable frequency converter, together with the constant frequency external power supply, to startthe aircraft engine, and thence to use the static frequency converter to supply constant frequency aircraft system power, thereby eliminating the need for the air turbine starter, associated plumbing, and external air supply source, with the attendant space and weight saving advantages thereby accruing.

This invention contemplates an alternating current machine arrangement comprising: an A.C. machine having a shaft and a pair of electromagnetic structures, each of which includes a stator and a rotor having polyphase windings, the polyphase windings of the rotors being connected for reverse phase rotation, and said rotors being carried by said shaft; first means for providing a polyphase output at a constant frequency; second means for providing a polyphase output at a variable frequency; a prime mover; and an electric load; wherein by having said first means connected to the stator winding of one of said electromagnetic structures for exciting said winding with said constant frequency output, and said second means connected to the stator winding of the other of said electromagnetic structures for simultaneously exciting said last mentioned winding with said variable frequency output, the shaft angular position is a function of the applied mechanical torque and proportional to the phase angle difference of the outputs from said first and second means when the frequencies of the outputs from said first and second means are equal, and the shaft rotates at a speed proportional to the frequency difference of the outputs from said first and second means when the frequencies of the outputs from said first and second means are different; and wherein by having said electric load connected to the stator winding of one of said electromagnetic structures, said second means connected to the stator winding of the other of said electromagnetic structures for exciting said last mentioned winding with a zero frequency output, and said prime mover coupled to said shaft, the stator winding of said one electromagnetic structure provides a polyphase output to said electric load.

In the drawings: Figure lisa sectioned plan view showing the A.C.

machine of the arrangement of the invention.

Figure 2 is an electrical schematic diagram showing rotor and stator winding connections of the A.C.

machine of the arrangement of the invention.

Figure 3 is a diagrammatic representation generally showing the arrangement of the invention and illustrating the operation thereof as a motor, position transducer or torque transducer.

Figure 4 is a diagrammatic representation generally showing the arrangement of the invention and illustrating the operation thereof as a generator.

With reference first to Figure 1,theA.C. machine disclosed includes a housing 2, a pair of electromagnetic structures 4 and 6, a shaft 8 common to the electromagnetic structures and supported in the housing at opposite ends by bearings and bearing supports 10 and 12, and a terminal block 14 supported by the housing for making electrical connections to the electromagnetic structures as generally illustrated in the Figure.

Electromagnetic structures 4 and 6 include laminated stator cores 16 and 18 suitably supported in housing 2 and carrying stator polyphase windings 20 and 22, respectively, laminated rotor cores 24 and 26 carrying rotor polyphase windings 28 and 30, respectively, and support structures 31 and 32 for supporting the respective rotor cores 24 and 26 on common shaft 8.

Stator winding 20 is wound with a plurality of phases and an integral number of pole pairs such as is well known in the art. Rotor winding 28 is wound with a plurality of phases, not necessarily the same number of phases as stator winding 20, and with an integral number of pole pairs equal to that for stator winding 20.

In a similar manner, stator winding 22 is wound with a plurality of phases and an integral number of pole pairs, but not necessarily the same number of phases or pole pairs as for stator winding 20.

Rotor winding 30 is wound with a plurality of phases equal to that of rotor winding 28 and with an integral number of pole pairs equal to that of stator winding 22.

The electrical interconnection 33 between rotor windings 28 and 30 is such as to reverse the phase rotation of the rotors as shown typically in Figure 2.

In this connection, it is noted that the stator and rotor connections are shown as three phase, wye connections, for purposes of illustration only. Other polyphase windings connected in other configurations are within the scope of the invention as well.

U.S. Patent 3,179,872, utilizes an A.C. machine of the kind described to provide a cascaded generator configuration. One phase of a stator is excited with DC current which produces a three-phase voltage of a specific frequency in the corresponding rotor. This voltage is transmitted to the other rotor with a reverse in phase rotation, as noted, and coupled to the other or output stator by both transformer and generator action which provides a voltage at an output frequency twice that generated in the first mentioned rotor. The invention utilizes a like A.C.

machine in a motor configuration as will be next described.

Reference is now made to Figure 3 wherein the A.C. machine shown in substantial detail in Figure 1 is designated generally by the numeral 40. Stator winding 20 (Figure 1) of electromagnetic structure 4 is energized by constant frequency polyphase power (shown as three phase) from an external power source 41, while stator winding 22 (Figure 1) of electromagnetic structure 6 is energized by the output of a variable frequency converter 47 (also shown as three phase) and powered by the aforementioned external power source 41 by means of a bus 46.In this condition, and with variable frequency converter 47 supplying polyphase power at the same frequency as external power source 41, the speed of shaft 8 is locked in synchronism at zero rotational speed and located at a rotational angle which is a function of the mechanical torque applied to shaft 8 and which is proportional to the difference between the electrical phase angle of electromagnetic structure 4 and the electrical phase angle of electromagnetic structure 6. In the same condition and with variable frequency converter 47 supplying polyphase power at a frequency other than the frequency of external power source 41, shaft 8 rotates synchronously at a shaft speed proportional to the difference between the electrical frequency of electromagnetic structure 4 and the electrical frequency of electromagnetic structure 6.

In regard to variable frequency converter 47, the converter is similar to that described in U.S. Patent 3,775,662, except that the device of the noted patent is a static arrangement including a constant frequency oscillator for providing the precise frequency controi required, while converter 47 includes a variable oscillator which is controlled for providing a variable output frequency.

Reference is now made to Figure 4 wherein the A.C. machine shown in substantial detail in Figure 1 is designated generally by the numeral 40. Stator winding 20 (Figure 1) of electromagnetic structure 4 is connected to an electrical load 49 (shown as three phase) by means of a bus 48, while stator winding 22 (Figure 1) of electromagnetic structure 6 is energized by the output of variable frequency converter 47 (also shown as three phase), and powered by exter nal power source 41 by means of bus 46. Shaft 8 is driven by a prime mover 51, being mechanically connected thereto by a suitable coupling 52.In this condition, and with the variable frequency converter 47 supplying zero Hz power (direct current excitation), polyphase power (shown as three phase) is delivered to the electric load 49 by means of bus 48 leading from stator winding 20 (Figure 1) of electromagnetic structure 4, and having an electrical frequency proportional to the rotational speed of shaft 8.

The arrangement herein disclosed may thus be used as a brushless alternating current rotational position transducer, a brushless alternating current torque transducer, a brushless alternating current synchronous motor, or a brushless alternating current synchronous generator. When used as a motor-generatorto both start an aircraft engine and, thence, supply electric power for ultimate use by the aircraft electric system, the advantageous elimination of the heretofore required air turbine starter and associated plumbing is achieved.

Claims

1. An alternating current machine arrangement comprising: an A.C. machine having a shaft and a pair of electromagnetic structures, each of which includes a stator and a rotor having polyphase windings, the polyphase windings of the rotors being connected for reverse phase rotation, and said rotors being carried by said shaft; first means for providing a polyphase output at a constant frequency; second means for providing a polyphase output at a variable frequency; a prime mover; and an electric load; wherein by having said first means connected to the stator winding of one of said electromagnetic structures for exciting said winding with said constant frequency output, and said second means connected to the stator winding of the other of said electromagnetic structures for simultaneously exciting said last mentioned winding with said variable frequency output, the shaft angular position is a function of the applied mechanical torque and proportional to the phase angle difference of the outputs from said first and second means when the frequencies of the outputs from said first and second means are equal, and the shaft rotates at a speed proportional to the frequency difference of the outputs from said first and second means when the frequencies of the outputs from said first and second means are different; and wherein by having said electric load connected to the stator winding of one of said electromagnetic structures, said second means connected to the statorwinding of the other of said electromagnetic structures for exciting said last mentioned winding with a zero frequency output, and said prime mover coupled to said shaft, the stator winding of said one electromagnetic structure provides a polyphase output to said electric load.

2. An arrangement as claimed in claim 1, wherein said second means is a variable frequency converter which is energized from said first means to provide the polyphase output at a variable frequency.

3. An arrangement as claimed in claim 1, wherein the stator winding of one of said electromagnetic structures is provided with a plurality of phases and an integral number of pole pairs, and the corresponding rotor winding is provided with a plurality of phases and integral number of pole pairs which is equal to the number of pole pairs of said stator winding.

4. An arrangement as claimed in claim 3, wherein said corresponding rotor winding is pro vided with a plurality of phases equal in number to the number of phases of said stator winding.

5. An arrangement as claimed in claim 3, wherein said corresponding rotor winding is provided with a plurality of phases of a number other than the number of phases of said stator winding.

6. An arrangement as claimed in claims 1 and 3, wherein the stator winding of the other of said electromagnetic structures is provided with a plurality of phases and an integral number of pole pairs.

7. An arrangement as claimed in claim 6, wherein the stator winding of said other electromagnetic structure is provided with a number of phases and pole pairs equal to the number of phases and pole pairs of the stator winding of said one electromagnetic structure.

8. An arrangement as claimed in claim 6, wherein the stator winding of said other electromagnetic structure is provided with a number of phases and pole pairs other than the number of phases and pole pairs of the stator winding of said one electromagnetic structure.

9. An arrangement as claimed in claim 6, wherein the rotor winding corresponding to the stator winding of the other of said electromagnetic structures is provided with a plurality of phases equal to the plurality of phases of the rotor winding of said one electromagnetic structure, and with an integral number of pole pairs equal to the number of pole pairs of said stator winding of said other electromagnetic structure.

10. An alternating current machine arrangement constructed and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.

wings.