Patent EA-001441-B1 (EA)
Title: An electrcal drive system for vehicles
Inventor: LEIJON MATS
IPC: H01F27/00
Filed: 1997-05-27
Abstract: 1. An electric drive system for driving vehicles, e.g. railway locomotives and motor coaches, in which electric power is transferred from a distribution network via an overhead conductor and at least one traction motor to the mechanical drive shafts of the vehicle, the system comprising at least one electric machine arranged between the distribution network and the drive shafts, each electric machine having at least one winding, characterized in that at least one of said machines has a winding comprising an insulation system consisting of at least two semi conducting layers, each layer constituting essentially an equipotential surface, and solid insulation therebetween. 2. A drive system as claimed in claim 1, characterized in that at least one of said layers has substantially the same coefficient of thermal expansion as the solid insulation. 3. A drive system as claimed in claim 1, characterized in that said at least one machine comprises a magnetic circuit with a magnetic core. 4. A drive system as claimed in claim 3, characterized in that the flux paths in the core of the magnetic circuit in said at least one machine (105, 116) in the plant consists of laminated sheet plate and/or rough forged iron and/or cast iron and or powder-based iron. 5. A drive system as claimed in any of claims 1-4, characterized in that the solid insulation is built up of a cable (6) intended for high voltage, comprising one or more current-carrying conductors (31) surrounded by at least two semiconducting layers (32, 34) with intermediate insulating layers (33) of solid insulation. 6. A drive system as claimed in claim 5, characterized in that the innermost semiconducting layer (32) is at substantially the same potential as the conductor(s) (31). 7. A drive system as claimed in either claim 5 or claim 6, characterized in that one of the outer semiconducting layers (34) is arranged to form essentially an equipotential surface surrounding the conductor(s) (31). 8. A drive system as claimed in claim 6, characterized in that said outer semiconducting layer (34) is connected to a selected potential. 9. A drive system as claimed in claim 8, characterized in that the selected potential is earth potential. 10. A drive system as claimed in any of claims 5-7, characterized in that the current-carrying conductor comprises a plurality of strands, only a few of the strands not being insulated from each other. 11. A drive system as claimed in any of claims 1-10, characterized in that the winding consists of a cable comprising one or more current-carrying conductors (2), each conductor consisting of a number of strands, an inner semiconducting layer (3) being arranged around each conductor, an insulating layer (4) of solid insulation being arranged around each inner semiconducting layer (3) and an outer semiconducting layer (5) being arranged around each insulating layer (4). 12. A drive system as claimed in claim 11, characterized in that the cable also comprises a metal screen and a sheath. 13. A drive system as claimed in any of the preceding claims, characterized in that the magnetic circuit contains air or other insulating gases. 14. A drive system as claimed in claim 3, characterized in that the winding(s) of the magnetic circuit, and also the permanently insulated connection conductors for high tension current between the system units are produced using a cable (6) with solid insulation for high voltage and comprising at least two semiconducting layers (32, 34), and also strands (36) which may be insulated or uninsulated. 15. A drive system as claimed in either claim 5 or claim 14, characterized in that the high-voltage cables (6) have a conductor area of between 30 and 3000 mm<2> and have an outer cable diameter of between 10 and 250 mm. 16. A drive system as claimed in any of the preceding claims, characterized in that the outer semiconducting layer (34) is connected to earth potential. 17. A drive system as claimed in any of the preceding claims, characterized in that one of said at least one of said machines is arranged between the distribution network and the supply line. 18. A drive system as claimed in claim 17, characterized in that said machine is a transformer for step-down transforming from the voltage level of the distribution network to the voltage level of the overhead conductor. 19. A drive system as claimed in claim 17, characterized in that said machine is a motor generator in which the motor is supplied with the voltage of the distribution network and the generator emits a voltage corresponding to the voltage level of the supply line. 20. A drive system as claimed in claim 19, characterized in that the rotor shaft of the motor is connected directly to the generator shaft. 21. A drive system as claimed in claim 1`9 or claim 20, characterized in that the generator is of single-phase type. 22. A drive system as claimed in claim 21, characterized in that the frequency of the is an integer part of the network frequency, preferably 16 2/3, 20 or 25 Hz. 23. A drive system as claimed in any of the preceding claims, characterized in that at least one of said at least one machine is arranged in the vehicle. 24. A drive system as claimed in claim 23, characterized in that said at least one machine arranged in the vehicle is a transformer for step-down transformation of the voltage of the overhead conductor to the voltage of the traction motor. 25. A drive system as claimed in claim 23, characterized in that the at least one machine arranged in the vehicle is at least one traction motor in the vehicle. 26. A drive system as claimed in claim 25, characterized in that said at least one traction motor is supplied directly with voltage from the supply line without intermediate connection of another electric machine. 27. An electric drive system intended for electrically powered vehicles, in which electric power is transferred from a distribution network via an overhead conductor, the system comprising an electric machine having at least one winding, said winding comprising an insulation system which comprises at least two semi-conducting layers, each layer constituting essentially an equipotential surface, and solid insulation therebetween. 28. A means as claimed in claim 27, characterized in that the machine is a transformer for step-down transforming from the voltage level of the distribution network to the voltage level of the overhead conductor. 29. A means as claimed in claim 28, characterized in that the machine is a motor generator in which the motor is supplied with the voltage of the distribution network and the generator emits a voltage corresponding to the voltage level of the overhead conductor. 30. A means as claimed in claim 29, characterized in that the motor generator comprises the features defined for the motor generator claimed in any of claims 21-23. 31. A means as claimed in either of claims 28 or 29, characterized in that the machine comprises the features defined for said at least one of the machines in any of claims 2-16. 32. A procedure for transmitting electric power from a distribution network to an overhead conductor intended for electrically powered vehicles, characterized in that the electric power is transmitted by a means as claimed in any of claims 28-32. 33. An electric machine in a vehicle such as a railway locomotive or a motor coach, in which the electric power is obtained from an overhead conductor, said machine being arranged to transmit the electric power from the overhead conductor to the drive shafts of the vehicle, and said machine being provided with at least one winding, characterized in tbat the winding comprises an insulation system consisting of at least two semiconducting layers, each layer constituting essentially an equipotential surface, and solid insulation therebetween. 34. An electric machine as claimed in claim 33, characterized in that the machine is a transformer for step-down transformation of the voltage of the overhead conductor to the voltage of a traction motor in the vehicle. 35. An electric machine as claimed in claim 34, characterized in that the transformer is cooled at earth potential. 36. An electric machine as claimed in claim 33 or claim 35, characterized in that the magnetic circuit of the transformer is of core or shell type. 37. An electric machine as claimed in claim 33, characterized in that the machine is a traction motor connected to the overhead conductor without an intermediate transformer. 38. An electric machine as claimed in any of claims 33-37, characterized in that the machine includes the features defined for said at least one machine claimed in any of claims 2-16. 39. An electrically powered vehicle which obtains driving power from an overhead conductor, characterized in that the vehicle is provided with at least one machine as claimed in any of claims 33-38.