What is the difference between modified sine wave and pure sine wave?

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What is the difference between modified sine wave and pure sine wave?

Inverters have either modified sine wave (square wave) or pure sine wave output.

Pure Sinewave Inverter
This is the best output waveform you can get out of an inverter and all appliances are able to run off it without interference or overheating. Some of its advantages are as follows:

  • Output voltage waveform is pure sine wave with very low harmonic distortion and the same as the ESKOM supply
  • Inductive loads like microwave ovens and motors run correctly, quieter and cooler
  • Reduces audible and electrical noise in fans, fluorescent lights, audio amplifiers, TV, Game consoles, Fax, and answering machines
  • Prevents crashes in computers, unreadable print outs, and glitches and noise in monitors
  • It can be efficiently electronically protected in overload, overvoltage, undervoltage and over temperature conditions

Modified Sinewave Inverter
The Modified sinewave inverter has limitations. These are some of the appliances that may experience problems when running off Modified Sinewave inverters:

  • Laser printers, photocopiers, magneto-optical hard drives
  • Some fluorescent lights with standard ballasts
  • Power tools employing “solid state” power or variable speed control
  • Some battery chargers for cordless tools
  • Produces sometimes interference in some television sets
  • Digital clocks with radios
  • Sewing machines with speed/microprocessor control
  • Medical equipment such as oxygen concentrators

Modified sinewave inverters are usually only protected by standard fuses which, under normal circumstances, are not always fast enough, therefore they are by far more vulnerable to failure.

It is definitely advantageous to use a pure sine wave inverter as a pure sine wave inverter can basically run any type of equipment in contrast to a modified sine wave / step square wave inverter.

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