| 摘要 |
PROBLEM TO BE SOLVED: To improve the performance of a frequency converter by restoring current at a low speed. SOLUTION: In a frequency converter for an AC motor equipped with an inverter O having switching elements Sa, Sb, Sc controlled by a control circuit CC fed from a DC bus B, and a shunt Sh located in the DC bus B for measuring a DC current flowing through the DC bus, if at least one of two components of an output voltage vector Vs is less than a predetermined value TMIN, one calculating means is provided for computing each of these two vector Vs' and vector Vs'', at least equal to the predetermined value TMIN, in such a manner that the vector average of these vector Vs' and Vs'' becomes equal to the output voltage vector Vs. |
