Method for determining motor speed of an induction motor for a hoist
AssigneeHarnischfeger Corporation
InventorKevin J. Anderson
Life of this patent
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Abstract
In a drive using an AC induction motor for moving a load in hoisting and lowering directions, a method for determining motor speed includes, in any order, the steps of selecting first and second voltage signals representing a maximum speed to be attained by the motor at rated output torque in the hoisting and lowering directions, respectively, and selecting a bias voltage. One of the voltage signals is combined with the bias voltage to obtain a feedback signal representing motor speed and the feedback signal is compared with a speed command signal to obtain a deviation signal representing the difference between actual and commanded motor speed. The drive is disabled if the difference is "out of" a predetermined range.
Claims14
In a drive using an AC induction motor for moving a load in hoisting and lowering directions, a method for determining motor speed including, in any order, the selecting steps of:
- selecting a first voltage signal representing a maximum speed to be attained by the motor at rated output torque in the hoisting direction;
- selecting a second voltage signal representing a maximum speed to be attained by the motor at rated output torque in the lowering direction;
- selecting a bias voltage;
- and further including the steps of:
- combining one of the voltage signals with the bias voltage to obtain a feedback signal representing motor speed;
- and,
- comparing the feedback signal with a speed command signal.
In an AC inverter drive connected to an AC induction motor for moving a load in hoisting and lowering directions, a method for determining motor speed including, in any order, the steps of:
- selecting a first constant representing a voltage per unit of motor speed in the hoisting direction;
- selecting a second constant representing a voltage per unit of motor speed in the lowering direction;
- selecting a bias voltage;
- and further including the steps of:
- determining actual motor speed and direction of rotation;
- multiplying the motor speed by one of the constants;
- combining the product with the bias voltage to obtain a feedback voltage signal;
- and,
- providing the feedback voltage signal to the drive.
Dependencies are inferred from the claim text.