If you first understand that MSW inverter puts out a square wave that has been modified to look somewhat like a Sine wave, you will understand why electric motors often do not like that source of power. Running a fan on a modified square wave output often and usually results in the fan "growling" as the input voltage jumps up and down across each half cycle of the inverter output. Variable speed hand drills also complain when used at half trigger settings. Running a modified square wave into a computer power supply, for example, does not cause problems because the input circuits in the computer power supply take what is given and do all sorts of electronic tricks to the power (sometimes called power conditioning) before presenting a seriously smooth voltage to the computer. Notice how most computer type power packs will operate on 100 to 230 Volt, AC, inputs? The alternating current requirement is so that transformers can be used to step up or down the input voltage to that required for the end device to operate.
I have a good quality Pure Sine Wave inverter to run a bar fridge (motor), a pedestal fan (motor), the wife's sewing machine (motor) and a spin dryer (motor). For everything else, a number of modified square wave inverters are matched in size to the devices they are used to power.
