-=> Quoting Theo Bee to John Tserkezis <=-

Hello Theo,

 JT>  ----      ----
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 JT> So much for "modified square wave".

 TB> That's exactly what that is.
 TB> To approximate a sine wave from a fixed voltage switching device there
 TB> are two criteria to meet.
 TB> You can't drop the peak voltage otherwise you have problems with
 TB> say microwave ovens or other devices that rely on peak voltage.
 TB> At the same time you can't deviate from the RMS value since you
 TB> then burn out globes or heater bars.

 TB> So to satisfy both you have to meet 

 TB> Integral(0 to pi ) of (Vm sinwt)^2 dt = Integral(0-t) of Vm^2 dt

 TB> Fortunately I don't ofhand remember the integrals solutions anymore
 TB> leaving it to you to solve.

 I used to know it too, but have long since forgotten, as well as lost my
notes from way back...

 I was first made aware of "modified square wave" as used in
inverters to look
like this:

      --
    -|  |-        -
  -|      |-    -|
            |  |
             -- 

 The drawing is a bit crude, but you get the idea.  So from my first
impression, a simple square wave with a dead time in between, does not cut it.

John Tserkezis, Sydney, Oz. Fidonet: 3:712/610  Internet: jt{at}suburbia.com.au

... Banksias make very suitable suppositories.
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