PURPOSE: To prevent the generation of a gear sound even at the time of a light load operation by a method wherein the helper torque output reference of a speed control circuit is compared with a prescribed constant and a torque reference is switched over.
CONSTITUTION: In the case when the helper torque reference signal of a speed control circuit 13 is lower than the helper torque reference constant of a torque computation circuit 16, switchover is made by a torque reference switch 14 so that a torque reference is inputted from a torque reference setting unit 17. Based on this input, the torque control circuit 12 converts a phase signal from a phase control circuit 10 and controls so that a helper motor 4 is made regenerative by a main circuit conversion device 8. When the helper torque reference signal of the speed control circuit 13 is higher than the helper torque reference constant of the torque computation circuit 16, switchover is made by the torque reference switch 14 so that the input of the torque reference to the torque control circuit 12 is made from the speed control circuit 13, and thereby the helper motor 4 is made to conduct a load sharing operation.
SEKINE SHIGERU
MURANO HIROYUKI
TOSHIBA CORP
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