Inverter 60 Hz Square Wave

Discussion in 'General Electronics Chat' started by Chacabucogod, Mar 2, 2015.

  1. Chacabucogod

    Thread Starter New Member

    Nov 16, 2013
    26
    1
    Hi,

    I was just reading about pure sine wave inverters and how they generate the suare pulse that feeds the transistors by comparing a trinagle wave and a 60 hz sine wave. My question is: why isn't a 60 hz square pulse generated with a dc offset and fed to the transistors, then filtered?

    Thank you.
     
  2. Roderick Young

    Member

    Feb 22, 2015
    408
    168
    I don't know, but would guess that in power conversion, efficiency is important, and it's better to generate an approximately correct waveform in the first place, than to apply massive subsequent waveshaping and filtering at high power. Not only would it be expensive, they would lose some of the power.
     
  3. crutschow

    Expert

    Mar 14, 2008
    13,056
    3,245
    If you calculate the size of the filter needed to get a decent sinewave, you will see why they don't.
     
  4. Ramussons

    Active Member

    May 3, 2013
    557
    92
    What actually happens is that the Square Wave is Modified by a technique called Pulse Width Modulation. The "ON" and "OFF" time of the Transistors is varied; the variation follows the Sine Wave.

    Read http://fab.cba.mit.edu/classes/MIT/961.04/topics/pwm.pdf

    The transistors are operated in ON/OFF mode since the power dissipation is least in these 2 states.
     
Loading...