Patent ID: 7245036

Claim:
An engine driven inverter controlled generator set comprising: a power supply unit that uses a generator driven by an engine as a power supply to output a DC voltage; an inverter device that converts the output voltage of said power supply unit into an AC voltage; a rotational speed detection unit that detects a rotational speed of said engine; and an engine rotational speed control unit that controls the rotational speed of said engine detected by said rotational speed detection unit so as to be kept at a target rotational speed suitable for a load applied to said inverter device, wherein said engine rotational speed control unit includes: load determination means for determining that a size of the load applied to said inverter device is above a set value; rotational speed determination means for determining whether the rotational speed of said engine detected by said rotational speed detection unit is reduced to a preset minimum rotational speed when said load determination means determines that the load above the set value is applied to said inverter device; on-load rotational speed control means for controlling so as to bring the deviation between the rotational speed detected by said rotational speed detection unit and a target rotational speed arithmetically operated by target rotational speed arithmetical operation means to zero when it is determined that the rotational speed of said engine detected by the rotational speed detection unit is not reduced to a minimum rotational speed, no-load state duration measurement means for measuring a duration when no load is applied, when the load determination means determines that no load above the set value is applied said the inverter device, and no-load state rotational speed gradual reduction control means for stepwise reducing the rotational speed by a predetermined range of reduction at fixed intervals to reduce the rotational speed toward the target rotational speed when no load above the set value being applied to said inverter device is detected.