This is a Low Frequency Inverter

Low frequency inverters are the pinnacle of electrical durability. Their massive iron core transformer is aptly capable of absorbing surge loads because of the “Flywheel Effect” inherent in the physical amount of a transformer’s iron. LF inverters have larger and more robust Field Effect Transistors (FET’s) that can operate cooler, in part due to the slower frequency of switching required to produce AC power.

These inverters are slightly larger and heavier than their low frequency counterparts but they more than make up for this with reliability. If you are running any sort of inductive load from pumps or motors then a low frequency inverters is a much safer choice.