Why is a modified sine wave harmful to electronics?

I was reading an article in a computer magazine about UPS (Uninterruptible power supplies). It said that UPSs produce a modified sine wave. However it said that using a modified sine wave to operate computers over long periods is harmful. I wonder how a modified sine wave could damage a computer. All it is is just a sine wave that steps instead of a perfect curve. Right? 

iceng5 years ago
Any non-sine wave ( has little square and even spiky waves ) which
cause additional heating in power transformers and stress input filters.

Any time you raise the heat and stress of any AC product you hasten
its failure :¬þ

iceng iceng5 years ago
PS the RMS ( Root Mean Squared ) is the heating value.

For a sine wave the heating value is a sine But add a little inductive spike
to the sine wave from a UPS and the RMS calculation increases dramatically and is validated in calorimetry heating tests.

A square wave or even a step wave has a much greater RMS then the
tame sine wave as you can read in my pointer reference.

If you want to compute RMS for yourself you will need to understand
how to manipulate electrical engineering mathematics in the frequency domain :)

See the Sine, Square, Triangle and Sawtooth waveforms pic.
Super_Nerd (author)  iceng5 years ago