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DC to AC Inverter FAQ

What is the difference between modified, pure sine wave inverters?
There are 3 major types of inverters - pure sine wave (or "true" sine wave), modified sine wave (actually a modified square wave), and square wave.

Pure Sine Wave A pure sine wave is what you get from your local utility company and from some pure sine generators (most generators are not pure sine).
  • major advantage of a pure sine wave inverter is that all of the equipment which is sold on the market is designed for a pure sine wave. This guarantees that the equipment will work to its full specifications.
  • Some appliances, such as motors and microwave ovens will only produce full output with pure sine wave power.
  • A few appliances, such as bread makers, light dimmers, and some battery chargers require a pure sine wave to work at all.
  • audio equipment, satellite systems, and video equipment, will run properly using pure sine wave inverters.
  • these are the most expensive of the inverter designs and outperform all other types of inverters, regardless of use.
Analog Pure Sine Wave The sine wave produced by an analog pure sine wave inverter, is very similar to that of the digital pure sine wave inverter. The key difference is that the analog switching causes noise or static on the ac wave.
  • generally most appliances, motors, microwaves, chargers, and power tools will produce full power and not cause any buzzing or negative effects.
  • these types of pure sine inverters are not recommended for medical equipment unless manufacturer approved.
  • use this inverter for electric shavers and emergency flashlights, garage door openers, laser printers and large strobes used in photography
Modified Sine Wave (quasi-sine) A modified sine wave inverter actually has a waveform more like a square wave, but with an extra step. A modified sine wave inverter will work fine with most equipment, although the efficiency or power of the equipment will be reduced with some.
  • Motors, such as refrigerator motor, pumps, fans etc will use more power from the inverter due to lower efficiency. Most motors will use about 20% more power. This is because a fair percentage of a modified sine wave is higher frequencies - that is, not 60 Hz - so the motors cannot use it.
  • Some fluorescent lights will not operate quite as bright, and some may buzz or make annoying humming noises.
  • Appliances with electronic timers and/or digital clocks will often not operate correctly. Many appliances get their timing from the peak of the line power - basically, the modified sine has a flat top rather than a peak - this may cause the occasional double trigger. Because the modified sine wave is noisier and rougher than a pure sine wave, clocks and timers may run faster or not work at all.
  • Items such as bread makers and light dimmers may not work at all - in many cases appliances that use electronic temperature controls will not control. The most common is on such things as variable speed drills will only have two speeds - on and off.
  • most equipment will operate without any noticeable difference, and because the lower cost, makes this the most common inverter sold and generally the only type found at your local retailer.
Square Wave Very few but the very cheapest inverters any more are square wave. A square wave inverter will run simple things like tools with universal motors with no problem - but not much else. These are seldom seen any more except in the very cheap or very old ones. Of course we don't sell these. Too cheap!

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