Difference between pure sine wave inverter and quasi sine wave inverter

Pure sine wave inverter real, output and household electricity. Modified sine wave, square wave, quasi sine wave can not be compared with the pure sine wave, with strong carrying capacity, no damage to electrical appliances. If you are using a modified sine wave or quasi sine wave motor with a type of electrical appliances (such as electric fans, pumps and other), you'll find out the electric fan rotates up "squeak" sound. If you take the television, audio, you'll find out a "buzz" sound, this is because the modified sine wave or quasi sine wave inverter output waveform caused by.