Electrical generator or motor structure – Dynamoelectric – Linear
Patent
1998-06-10
2000-04-25
Ramirez, Nestor
Electrical generator or motor structure
Dynamoelectric
Linear
H02K 4100
Patent
active
060547839
DESCRIPTION:
BRIEF SUMMARY
FIELD AND BACKGROUND OF THE INVENTION
The invention relates initially to a synchronous linear electric motor with a secondary part containing several permanent magnets arranged in a certain pole grid, and with a primary part that can move relative to the secondary part and whose position relative to the secondary part can be determined by a travel measurement system.
The invention also relates to a method for determining the commutation offset in a synchronous linear electric motor.
In order to ensure a force of the synchronous linear motor that is constant over time, an angle of 90.degree. must be set between the field vector of the primary part and the field vector of the secondary part. This means that the motor control of the primary part must operate as a function of the current position of the location of the permanent magnet poles of the secondary part. Therefore, the motor control requires the current actual position values of the primary part relative to the secondary part. A travel measurement system is provided for the purpose, which supplies this information for motor control.
In synchronous motors in general, following mechanical assembly, there is initially no unambiguous relationship between the field vectors of the primary and secondary parts. This relationship is clearly established during the initial startup of the drive by determining the so-called commutation offset.
SUMMARY OF THE INVENTION
It is an object of the invention to design a synchronous linear electric motor in such fashion that it can be put in operation in simple fashion with economical manufacture and reliable function. In addition, a high degree of safety must also be ensured during assembly. A simple method must also be specified for startup.
A simple startup is possible with a synchronous linear electric motor in accordance with the invention. In such a synchronous linear electric motor, a mechanical marking is provided on the secondary part with a known relationship to the pole grid of the permanent magnets. Such a marking can be used to determine the position of the primary part relative to the permanent magnets of the secondary part, and hence the commutation offset. After a relationship has been established between the commutation offset and the position of the primary part at the moment as determined by the travel measurement system, the motor control can control the windings of the primary part such that an angle of 90.degree. is set between the field vectors of the primary and secondary parts.
A method according to the invention is especially favorable for determining commutation offset, according to which claim the commutation offset is calculated from the distance determined between the mechanical marking on the secondary part and the primary part as well as the position of the marking to the pole grid internally in the motor control device.
Preferably, according to a feature of the invention, the relationship of the mechanical marking to the pole grid of the permanent magnets is stored in a nonvolatile manner in an electrical motor control device.
Advantageously, an absolute travel measurement system is used as the travel measurement system. The commutation offset then does not have to be determined again after each time the motor control device is switched off, but only when changes are made in the travel measurement system or when mechanical reconstruction with modified mounting conditions of the primary or secondary parts has been performed.
Mounting bores are usually provided on the secondary part of the synchronous linear electric motor, said bores serving to fasten the secondary part to the machine bed. It is favorable to use a mounting bore of the secondary part directly or indirectly as a mechanical marking.
Several mechanical markings with the same position relative to the pole grid of the permanent magnets of the secondary part can also be provided. The term "same position relative to the pole grid" means that the mechanical markings are located exactly in the middle of a north pole of the second
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SU 1 486 794 A (Inst Nadezhnosti Dolgovechnost) Jun. 15, 1989.
Philipp Werner
Schemm Eberhard
Schnurr Bernd
Farber Martin A.
Jones Judson H.
Ramirez Nestor
Rexroth Indramat GmbH
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