Hi Guest,

You are using the term "harmonics" ... being a non electrical person...

IGBT stands for "insulated gate bipolar transistor" and used generally designing AC motor drivers - inverters-.They r not used for AC2DC conversion.

SMPS stands for "switching mode power supply" that has smaller diemensions and more capacity with respect to power supply with transformer at equivalent power rate.

I don't know "FETA" what is stand for..?

IGBT, SCR, Thyristors, MOSFET, FET, GTO, IGSCR... are all switches used to interrupt or permit the flow of current. Depending on the circuit topology, you can change the DC voltage, turn AC to DC, or DC to AC etc... They all have their strength and weaknesses. They are used for different applications to their optimum performances. Only a salesman that doesn't know any better will tell you that one switch is always better than another. It just depends on the application.

If you want to know the details, read one of the many books about power electronics. There are tons of things that you can do with those switches if you are patient enough to learn the trade.

A simple explanations for harmonics is that they are like unwanted vibrations on the electrical current (faster than the AC frequency). Just like in your car transmission, a little is ok but too much will eventually cause damages. It is the circuit configuration that will cause harmonics, not the switch used.