Operation control method for engine-driven electric generator and engine-driven electric generator for driving a submersible pump for drainage

An engine-driven electric generator comprising;

• an engine;
• an electric generator driven by the engine;
• an inverter device that converts an alternating current (AC) input from the electric generator into a converted AC output having a predetermined frequency, the inverter device outputting the converted AC to a submersible pump;
• a three-phase output terminal block connected to the inverter device, the three-phase output terminal block also connected to the submersible pump, the submersible pump placed in a water source;
• a detector connection port for connecting a detector, the detector being a float type water level sensor or an electrode type water level sensor for detecting a water level of the water source, the detector connection port receiving a detection signal input from the detector;
• and
• a controller that controls operation of both the engine and the inverter device based on the detection signal input from the detector via the detector connection port,
• wherein the engine-driven electric generator has a standby state in which both the engine and an output of the inverter device are stopped;
• when the controller determines, based on the detection signal from the detector, that the water level of the water source is equal to or higher than a predetermined upper limit water level and the engine-driven electric generator is in the standby state,
• the controller starts the engine, then the controller operates the engine at a predetermined rated rotation speed;
• and then
• the controller operates the inverter device to gradually increase a frequency of the converted AC output from zero frequency to a predetermined set frequency to suppress an increase in a starting current of the submersible pump;
• and
• when the controller determines, based on the detection signal from the detector, that the water level of the water source is lower than a predetermined lower limit water level and the engine is operating at the rated rotation speed,
• the controller stops the converted AC output of the inverter device;
• and
• the controller stops the engine after the converted AC output of the inverter device is stopped, thereby returning the engine-driven electric generator to the standby state.