Inverter apparatus for preventing an overincrease of output frequency

摘要

An inverter apparatus using a microcomputer control system suitable for use in driving an ac rotary electric machine is concerned. The inverter apparatus includes a device for detecting an output current or an output voltage of the inverter apparatus or a control signal supplied to the inverter apparatus and, from the detected result, detecting an output frequency of the inverter apparatus and a switch structure having memory function by means of change-over and selection of lines for holding data for setting therein an upper limit of the output frequency of the inverter apparatus in hardware manner. Thus, the device for detecting the output frequency of the inverter apparatus produces the output frequency of the inverter apparatus and the switch structure produces the exact upper limit of the output frequency which is not influenced by noise or the like. The comparison therebetween can suppress the output frequency of the inverter apparatus to the upper limit always reliably without permanent change due to noise or the like and a fear of changing data so that occurrence of over-rotational speed operation of the driven ac rotary electric machine can be prevented sufficiently.