| 摘要 |
PURPOSE:To continue the operation, where only the current ingredients contributing to torque are reduced with the magnetic flux inside a motor maintained constant, even in the case where it has gotten in the operating condition to suppress overcurrents by stopping the progress of the phase of pulse width modulating voltage, so that it may get in return condition, when a load supply current exceeds the limit value. CONSTITUTION:When load currents increase during operation of an induction motor, and an overcurrent judgement signal S1 is output from a comparison circuit 25, this is supplied to a return condition forming circuit 22 and an integrator 24. Thereupon, the integrator 24 stops the integration, and stops the progress of a voltage phase theta*, and the return condition forming circuit 22 changes the switching element of an inverter main circuit over to return condition, and suppresses the increase of current. Hereby, even in the case that it has gotten in overcurrent suppressing condition, the operation can be continued by reducing the current ingredients contributing to torque, while maintaining the magnetic flux inside a motor constant. |
