Electricity: motive power systems – Plural – diverse or diversely controlled electric motors – Parallel connected motors
Reexamination Certificate
2000-03-02
2001-06-12
Ro, Bentsu (Department: 2837)
Electricity: motive power systems
Plural, diverse or diversely controlled electric motors
Parallel connected motors
Reexamination Certificate
active
06246192
ABSTRACT:
The invention concerns to electrical drive systems with a plurality of differently located AC motors having no slip rings nor commutators, the respective stator of said AC motors being designed so that it is adapted to generate a rotating magnetic field, furthermore with an electrical line network for supplying electrical energy from a power source to said AC motors, and with a control system comprising control units respectively allocated to said AC motors. Such electrical drive systems are located e. g. on large machines having a multitude of asynchronous drive motors for band conveyors which, for avoiding jams of conveyed articles, have to be switched on and switched off, respectively in predetermined sequence.
However, in case that an electrical drive system comprises a plurality of differently located motors which, for fulfilling their driving function, each need a speed control or a speed control with feedback, one uses regularly DC motors or universal motors the speed of which is controllable by controlling the terminal voltage, said DC motors or universal motors, because of the slip rings or commutators necessary for supplying current to the rotor, are comparatively expensive and, moreover have the drawback of sparking occurring at the slip rings or commutators, with this sparking causing interferences in a very broad frequency band and, thus, being in contradiction with the requirements of electromagnetic compatibility (EMC). Shielding of the interferences induced by slip ring or commutator sparking causes considerable problems as these interferences also invade the entire line system which then acts as an antenna for interference signals.
With known electrical drive systems of the kind defined before at the beginning having diverse AC motors as driving motors and wherein the driving motors fulfil remarkably different driving functions, it is moreover necessary that the control system comprises control units of correspondingly different design allocated to the respective AC motors, whereby, if such control units, in turn, are to be centrally controlled, a rather complicated system of control lines has to be installed between the central control station and the particular control units substantially parallel to the line network serving for supply of the electric energy.
This system of control lines for an electrical drive system with numerous electrical actuators, as far as such actuators are located in comparatively small distances on a frame or a supporting structure, is commonly implemented as a cable harness which is attached to the housing or supporting platform as a part to be handled during assembling, and causes high expenditure of labour and cost with its production, its assembly and its electrical connection to the central control station on the one side and to the particular control units for the actuators or drives, on the other side.
Control line systems of this known type, moreover, are sensitive to interference, tend to rupture of particular line wires under vibration and, with line defect caused malfunction of the motors to be controlled, can lead to severe malfunctions of the whole drive system.
In consideration of this state of the art it is an object to be achieved by the invention to design an electrical drive system of the general kind as defined above at the beginning in such manner that, with comparatively simple structure of a control system having control units allocated to a number of AC motors fulfilling different drive functions, the electromagnetical compatibility is ensured and brake-downs are avoided.
This object, in accordance with the invention, is achieved by the features of the characterising part of patent claim
1
.
Advantageous further developments and embodiments of the electrical drive system defined in patent claim
1
are subject matter of the patent claims following claim
1
.
The concept underlying the invention substantially is to supply control signals from the central control station to the AC motors via a line network which, coincidentally, is the energy supply network, whereby said control signals are not merely the conventional switch on signals and switch off signals for actuation of motor switches or the like but directly take influence on generation of the rotating magnetic field of the stator windings of the AC motors. Independent from whether the electrical line network of the electrical drive system presently disclosed is supplied with DC or AC the particular AC motors can be allocated respectively to the universal control units which, despite of respectively equal structure, can control AC motors of different power, different range of operating speed and different stator winding design. A cable harness connecting particular AC motors and the corresponding control units to a central control station need not be installed.
It is noted here generally that, while in the following description of embodiments the use of synchronous motors as AC motors having no slip rings and no commutators is demonstrated, the present invention comprises also the use of asynchronous motors with short circuit rotor as well as the use of motors of special design as split-phase machines. It is of significance that the motors suggested here for the drive system have no slip rings nor commutators and include a stator the stator winding of which is adapted to generate a rotating magnetic field. If the speed of the rotating field, as it is the case with use of asynchronous rotors, does not correspond with the rotor speed, it is obligatory in the system presently suggested to control the speed of the rotating magnetic field by the central control station, controlling the rotor speed for some drive functions, particularly for realising a desired start-up characteristic. Such speed controlling does not cause substantial difficulties since the operation of the AC motors having no slip rings and no commutators as used in the present case, is anyhow not dependent from the frequency of the current source, which in the system presently disclosed can be optionally a DC source or a AC source having a AC frequency as used internationally.
REFERENCES:
patent: 4263535 (1981-04-01), Jones
patent: 4289997 (1981-09-01), Jung et al.
patent: 4644232 (1987-02-01), Nojiri et al.
patent: 4774441 (1988-09-01), Toyomasu et al.
patent: 4825133 (1989-04-01), Tanuma et al.
patent: 4918365 (1990-04-01), Tanuma et al.
patent: 5162709 (1992-11-01), Ohi
patent: 5270632 (1993-12-01), Hirota et al.
patent: 5534758 (1996-07-01), Yamamoto et al.
patent: 5739648 (1998-04-01), Ellis et al.
patent: 6121735 (2000-09-01), Igeta et al.
patent: 0 256 769 (1988-02-01), None
patent: 0 275 992 (1988-07-01), None
patent: 0 500 948 (1992-09-01), None
Patent Abstracts of Japan; vol. 005, No. 121 (E-068), Aug. 5, 1981 & JP56058794 A (Fuji Electrochem Co Ltd), May 21, 1981—see abstract.
Patent Abstracts of Japan, vol. 095, No. 001, Feb. 28, 1995 & JP06296398A (Topcon Corp), Oct. 21, 1994—see abstract.
Fish & Richardson P.C.
Ro Bentsu
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