What is the difference among the different types of inverters?
There are three basic types of inverters: square wave, modified sine wave, and sine wave. Square wave inverters simply reverse the polarity of the DC voltage 120 times per second. (Each cycle consists of two polarity reversals.) Their output is basically either +120V or -120V. Square wave inverters tend to produce a lot of “hum” in equipment connected to them and cause motors to run hotter than normal. They are no longer in common use in solar electric systems. Modified sine wave inverters can also be considered “modified square wave inverters.” Their output consists of 4 voltage changes per cycle — 0, +peak, 0, -peak, and back to 0. Most of these vary the percentage of the cycle that voltage is either +peak or -peak depending on the load (this is called pulse width modification or PWM). The peak voltage (+ or -) is usually set so that the average value of the voltage is approximately 120V under normal conditions. Modified sine wave inverters are relatively inexpensive and will run mo
