My friend Paul at IBM seeems to say not to worry too much about destroying
your triacs. He raises the question as to whether the devices we have been
talking about might obtain the sine wave by a cheap method of simply
sticking a filter capacitor across a square wave.

>Date: Sun, 5 Nov 1995 20:51:58 -0500
>From: roossin@watson.ibm.com (Paul Roossin)
>To: drew@interport.net
>Subject: Inverter To Destroy Triac Devices?
>
>Almost all power supplies that I know of for consumer electronics have
>the same design, without triacs.  Maybe since a laser printer has some
>high voltage components, they are a little different.  I still doubt they
>need a triac.
>
>After the voltage is stepped down by a transformer, the AC is rectified
>and then smoothed (filtered), then regulated.  If there are high freq
>components to the 60Hz input, then there is inefficiencies (for instance,
>the transformer will choke off the higher freqs and heat up).  But I cannot
>see where damage can take place.
>
>If the output of the inverter is simply a "chopped" 117V (square) wave,
>then the real danger is putting this through inductive devices like
>motors.  It can burn out the fine magnet wire.  This is like burning
>out a speaker coil by sending in a clipped waveform.
>
>BTW, often modified sine means only that there is a filter capacitor across
>the output of the chopped wave.  I'll explain further next time we meet.
>Paul.
>
>
___________________________________
Derek Drew
drew@interport.net (main address for e-mail)
derekdrew@aol.com (alternate/backup address, checked infrequently)