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Abstract

The present invention provides a control method and a controller for an AC motor in which the AC motor can be continuously operated without using a device for returning a regenerative resistance or a regenerative energy to a power source and without raising the voltage of a main circuit to an over-voltage level. The control method and the controller for the AC motor includes a power converter (1) for outputting electric power to the AC motor (5); a torque limiting unit (6) for limiting a torque command relative to an arbitrary torque command; a voltage command calculating circuit (7) for calculating a voltage command on the basis of the torque command limited by the torque limiting unit (6) to control the electric power of the power converter (1) and a switching pattern generating circuit (8). The main circuit voltage of the power converter (1) is detected by a voltage detector (9). The torque limit value of a regenerative side is calculated in accordance with the level of the detected value in a regenerative side torque limit value calculating circuit (10) and set as the limit value of the torque limiting unit (6).

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First Claim