Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Mechanical measurement system
Reexamination Certificate
1997-09-26
2001-03-20
Wachsman, Hal (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Mechanical measurement system
Reexamination Certificate
active
06205405
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device for identifying the resistive torque of an item of equipment driven in rotation by an asynchronous electric motor, which is particularly suited to identifying a type of equipment with which a centrifuge is equipped, as well as for controlling operating parameters of the centrifuge.
DESCRIPTION OF THE RELATED ART
In the prior art, resistive-torque identification is based on calculating the moment of inertia of the item of equipment and thus requires the use of special sensors and a complicated calculation unit.
SUMMARY OF THE INVENTION
The purpose of the invention is to provide a device for identifying the resistive torque of an item of equipment rotationally driven by an asynchronous electric motor with a view to identifying the type of equipment, which is of a simple structure and does not require the provision of special sensors and a complicated calculation unit.
Another purpose of the invention is to provide a system for controlling or regulating operating parameters of a centrifuge on the basis of the knowledge of the type of equipment being driven by the motor.
Its subject is therefore a device for identifying the resistive torque of an item of equipment driven in rotation in association with an asynchronous electric motor operated by a control unit delivering to the said motor an alternating power-supply voltage for controlling the rotational speed of the said motor, characterized in that it comprises means for measuring the rotational speed of the said motor, means for calculating a characteristic that represents the motor slip and, associated with the said calculation means, means for comparing the calculated value of the said characteristic with a set of predetermined slip values stored in a memory associated with the said comparison means and each corresponding to a resistive torque value, so that the resistive torque value of the said item of equipment can be identified.
Advantageously, the means for calculating the characteristic that represents the slip of the motor comprise means of comparing the synchronous speed of the magnetic field generated by the power-supply voltage with the measured rotational speed of the motor.
According to another feature of the invention, since the said characteristic that represents the slip of the motor is a characteristic that depends on temperature, the device further includes means for measuring the air temperature around the item of equipment with a view to increasing the accuracy with which the resistive torque is identified.
As a preference, the rotationally driven item of equipment consists of the rotor of a centrifuge.
Another subject of the invention is a system for monitoring the operation of a centrifuge comprising an asynchronous electric motor operated by a control unit delivering to the said motor an alternating power-supply voltage for controlling the rotational speed of the said motor, characterized in that the control unit comprises a resistive-torque identification device as defined hereinabove and in that the said control unit comprises means for comparing the resistive torque value for the rotating item of equipment delivered by the said resistive-torque identification device with a resistive torque value stored in the said control unit and corresponding to the resistive torque of an item of equipment that the motor is allowed to drive at a given rotational speed, with a view to monitoring the compatibility between the rotationally driven item of equipment and the motor.
According to a specific embodiment, the control unit comprises means of limiting the rotational speed of the said item of equipment, these means being designed to limit the rotational speed of the said item of equipment to a maximum permitted value of the rotational speed of the said item of equipment.
Another subject of the invention is a system for controlling operating parameters of a centrifuge of the type comprising an asynchronous electric motor operated by a control unit delivering to the said motor a power-supply voltage for controlling the rotational speed of the said motor and rotationally driving a rotor arranged in a chamber and means for regulating operating parameters of the said centrifuge, characterized in that it comprises a resistive-torque identification device as defined hereinabove, and in that the said control unit comprises means for storing a set of resistive torque values each corresponding to a type of rotor and each associated with a set of parameters for regulating the operation of the said centrifuge corresponding to the said type of rotor, and means for comparing the resistive torque value delivered by the said resistive-torque identification device with the said values stored in the said memory means with a view to identifying the type of rotor with which the said centrifuge is equipped and delivering to the regulation means the values of the regulation parameters corresponding to the said rotor.
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Jouan
Larson & Taylor PLC
Wachsman Hal
LandOfFree
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