Modified Sine Wave Inverter
An inverter type that approximates the sine curve with a stepped square wave. Its circuit is simpler and needs no filtering stage; in return, because its harmonic content is high, it can produce heating and humming in motorised and electronically controlled appliances.
In this type the output is a wave that waits at the zero level and then moves to positive and negative steps. Its effective value is set to 230 V, but its peak value and transition rates differ from a sine wave. The filters inside appliances and motor windings see this difference as heat.
The loads that tend to give trouble in practice are these: compressor coolers, small tools with induction motors, some switching adapters, dimmed lighting and precision measuring instruments. Simple resistive loads generally work.
In an RV the second disadvantage of this type is electromagnetic noise. The sharp step transitions produce broadband interference; this noise can show itself in the vehicle radio, in wireless sensors and in short-range wireless links. If you are having connection trouble with devices managed over Bluetooth, such as a levelling system, repeating your tests with the inverter switched off is a good diagnostic step. If you do not want to be restricted in the range of appliances, a pure sine type is the safer choice for an RV.
The context in which this term is used: RV automatic levelling guide