Pure Sinewave
Normal AC Mains, given to us from Eskom is of a pure sinewave nature, it has very little harmonic distortion, subject to outside interference, such as lightning and large AC Loads ETC. All AC equipment in the stores today have been designed to run off a Pure sinewave wave form, including Computers, Motors, certain Lights ETC. The internal components of the inverter/UPS inverts the incoming DC Voltage into a sinewave wave form, but because of the sophistication of these components, this makes the Inverter/UPS more expensive.
Modified Sinewave
Modified sinewave has been created to save cost, modified sinewave inverters and UPS systems just switch their DC supply between positive and negative poles to give you a simulated sinewave wave form. Modified sinewave inverters and UPS systems are very cheap to produce but could be very costly if installed onto the incorrect equipment, for example, motors, Fluorescent globes with standard ballasts, anything with a high inrush or speed control or anything that has sensitive information stored on it, or is of a sensitive nature itself.
Please note, some UPS systems most notably the 600VA, under the desk type UPS systems are modified sinewave, but because a PC only runs off the inverter for a short period, when there is a power failure, they are less likely to be damaged as a result from the modified wave form.
