Electricity: motive power systems – Plural – diverse or diversely controlled electric motors – Plural linear-movement motors
Patent
1998-03-30
2000-01-04
Ramirez, Nestor
Electricity: motive power systems
Plural, diverse or diversely controlled electric motors
Plural linear-movement motors
318135, 318 41, H02P 774
Patent
active
060113677
DESCRIPTION:
BRIEF SUMMARY
Control device for linear-motor-driven equipment The invention relates to a control device for linear-motor-driven equipment, in particular for the drive of tenters of a film stretching plant, according to the precharacterizing clause of claim 1.
Linear-motor drives are known, for example, from U.S. Pat. No. 5,036,262, U.S. Pat. No. 4,853,602, U.S. Pat. No. 4,825,111 or U.S. Pat. No. 4,675,582. Drive systems of this type based on a linear-motor drive can in principle be used not only in the production of plastic film within the context of a stretching plant but also in other areas, as is described, for example, in U.S. Pat. No. 4,853,602.
Concatenated linear synchronous motor systems comprise, as so-called primary parts, a multiplicity of zones that are connected one behind another and have stator windings which can be activated at different phase angles with preselectable current amplitudes. The activation is carried out via converters or frequency converters, which comprise an appropriate output, power or driver stage or have a stage of this type connected downstream.
Along these primary parts, that is to say along the linear-motor system that comprises the stator windings and is organized into a plurality of zones that are connected one behind another, so-called secondary parts can then be moved over the magnetic field generated. In the case of film stretching plants, these secondary parts are so-called tenters.
The converters disclosed by U.S. Pat. No. 4,853,602 each have a dedicated control part, which comprises a computing unit having address counters, memories, selection logic etc., which are connected to a central control unit via a bus. Stored in the memories are profiles which represent three-bit pulse patterns as a function of time. They are addressed by address counters which, for their part, are activated by clock signals from the timebase of the central control unit. The profiles are selected such that the transition from one sector into the next can take place in an overlapping manner at identical frequency and phase angle.
A linear drive for in-house transport systems has also been disclosed by U.S. Pat. No. 4,876,966. In this case, the stator is subdivided into a multiplicity of sectors, each of which is fed from a converter. Speed profiles are generated and processed in the computing units through transferred boundary conditions (maximum speed, acceleration, etc.). The matched transition from one sector into the next is functionally necessary.
Further ore, it can be taken from the prior publications U.S. Pat. No. 5,274,317, EP 417 805 A1 and U.S. Pat. No. 5,113,125 that the calculation of the invertor switching patterns via the time variation of current amplitudes and phase angle is usual. In the case of digital processing, the dependence of these variables on the clock results from the time variation.
The active synchronization of the invertor timebases is likewise fundamentally known from U.S. Pat. No. 5,530,323. The converters assigned to the stators each have a timebase with a timer. These timebases are synchronized by pulses from and to the central unit.
In the case of the abovementioned linear synchronous motor systems, insofar as all the converters are activated in real time by a central computer or control unit, it is necessary to take account of the fact that, for example, at an initial frequency of 60 Hz (corresponding to a speed of 6.6 m/s and a pole pitch of 0.055 m) and at a resolution of 360.degree. in 6 steps, in the case of 150 converters 3 bits have to be transmitted every 2 ms over the communication bus structure which therefore leads, at 16.6 ms/8, to a net data rate of 150*3*500=225 kBaud, and this has to be done with a high requirement on the time accuracy.
More recent generations of frequency conversion allow a sine-wave modulation rather than simulating the output current in 6 steps (that is to say in the manner of a six-step drive). This requires a finer predefinition of the set point. The requirement on the transmission medium (data bus structure) increases quadra
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Kreiner Rudolph
Oedl Gunter
Zintz Wolfgang
Bruckner Maschinenbau GmbH
Jones Judson H.
Ramirez Nestor
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