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Anonymous Poster

IGBT, SMPS and like

07/05/2008 2:04 AM

Would some readers explain variouis elctronics control like IGBT /SMPS/FETA in respect to its use with conversion of AC to DC by say Thyrsitors, for Chargers/ Discargers . Being a non electrical person , but coming accross these names frequently , I would like to know

what are the purpose of using these?

What it replaced technically from previous systems/controls?

what are their limitations?

Can they be used as short circuit protection when several units are in use parallely from same transformer?

How can they be used for converting DC to AC and feed the supply lines?

Do their use cause any harmonics ?

Are there any systems similar to these or some new developements have taken place ?
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Snaketails
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Join Date: Sep 2007
Location: Wrong end of the yellow brick road in Oz
Posts: 930
Good Answers: 15
#1

Re: IGBT, SMPS and like

07/06/2008 8:23 PM

IGBT = Insulated Gate Bi-polar Transistor - Usually the output stage to convert the DC to your output voltage/frequancy

SMPS = Switch Mode Power supply

FETA = a type of cheese

FET = Field Effect Transistor

MOSFET = Metal Oxide Silicate Field Effect Transistor

Thyristor = A type of SCR

SCR = Silicone Controlled Rectifier

GTO = A type of printing machine, used to be used for printing money, or in Electronics, a Gate Turn Off, similar to a SCR, but the Gate turn off the device during the waveform, not turn it on

IGBT's can also take the incoming AC and convert it directly to the required output, can be quite tricky, and messy when these little buggers loose their guts all over your nice motordrive (a clear jelly stuff, looks like a jelly fish had exploded)

These days, the incoming AC is rectified to DC then converted back to AC from there.

For DC motor drives (180VDC out) you take the AC and switch it with a SCR bridge, these utilise 3 diodes and 2 SCR's, the common configuration I have used, is as follows.

Diode1 from -ve -> AC1

Diode2 from -ve -> AC2

Diode3 from +ve -> -ve

SCR1 from AC1 -> +ve

SCR2 from AC2 -> +ve

Diode 3 is the "Freewheeling diode"

The 3-ph drives I have built were mainly "Step" waveform drives, which output 0, 50%, 100%, 50%, 0%, -50%, -100%, -50%, 0% for the cycle power generation, the speed was governed by the cycle speed of that "Square" waveform.

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feridun
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Join Date: Jun 2008
Location: TR
Posts: 142
Good Answers: 1
#2

Re: IGBT, SMPS and like

07/06/2008 8:31 PM

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..?
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marcot
Guru
Canada - Member - Specialized in power electronics

Join Date: Feb 2008
Location: Montreal, Canada.
Posts: 1372
Good Answers: 80
#3

Re: IGBT, SMPS and like

07/07/2008 9:57 AM

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.

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