Hyundai DHY6000LE User Manual page 7

First startup
3.3 Stopping the generator
Turn the differential to the "OFF" position (down, Fig 9) and disconnect the
equipment connected to the control panel.
(If you miss this step, you may damage the voltage regulator AVR).
To stop the engine, turn the key or turn the switch (depends on
version) to "OFF" position (Fig 10).