Re: MOSFET/IGBT power supply?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "rheidlebaugh by way of Terry Fritz <twftesla-at-qwest-dot-net>" <rheidlebaugh-at-zialink-dot-com>

Colin: your comments are quite correct, I do however wish to add a small bit
of councel. Past all rectifiers had in addition to capacitive filtering a
choke (coil) in series to protect the rectifiers from surge current. With
robusk solid state devices the size of the coil is reduced, but I still hold
to the consept of using a choke in serirs with rectifiers to protect them
from current surges. Protection is often cheeper than repair.
  Robert  H

> From: "Tesla list" <tesla-at-pupman-dot-com>
> Date: Fri, 21 Jun 2002 07:57:21 -0600
> To: tesla-at-pupman-dot-com
> Subject: Re: MOSFET/IGBT power supply?
> Resent-From: tesla-at-pupman-dot-com
> Resent-Date: Fri, 21 Jun 2002 07:58:47 -0600
> 
> Original poster: "colin.heath4 by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <colin.heath4-at-ntlworld-dot-com>
> 
> hi
> the need for smoothing caps is arguable as when run through a six pulse
> rectifier. this is the main point of using the six pulse design
> the unit leaves you with quite a small amount of ripple as you are only left
> with the peaks of the waveform
> cheers
> colin heath
> ----- Original Message -----
> From: Tesla list <tesla-at-pupman-dot-com>
> To: <tesla-at-pupman-dot-com>
> Sent: Thursday, June 20, 2002 6:39 PM
> Subject: Re: MOSFET/IGBT power supply?
> 
> 
>> Original poster: "Eddie Burwell by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <eburwell-at-columbus.rr-dot-com>
>> 
>> At 08:08 AM 6/20/02 -0600, you wrote:
>>> Original poster: "Mr Gregory Peters by way of Terry Fritz
>> <twftesla-at-qwest-dot-net>"
>> 
>> <snip>
>> 
>>> Firstly, I would rectify the 240 VAC 3 phase supply using a six pulse
>>> rectifier, giving me 340 VDC. I would then switch this using mosfets or
>>> igbts at the line frequency (50Hz). Switching would be done using, say,
>>> a 555 timer. I would control the RMS current draw by varying the pulse
>>> width. This would then be fed to my 10kW single phase pole pig. I guess
>>> the core would heat up a bit, but apparently silicon steel isn't too bad
>>> at handling a square wave for short periods. Questions:
>>> 
>>> 1. Is this possible?
>> 
>> yes
>> 
>>> 2. What complications would I run into?
>> 
>> Your DC filter caps would need to be able to handle the ripple current.
>> any other problems would be specific to your circuit design.
>> 
>>> 3. Can the pole pig really handle a low frequency (50Hz) square wave?
>> 
>> Sure. Square wave will probably have slightly higher core losses than sine
>> wave.   For tesla coil duty it should be no problem. You could also up the
>> frequency of operation which would allow you to push more power through a
>> given core. this would also increase core losses.
>> 
>>> 4. Suggestions?
>> 
>> Look at Marco Denicolai's power supply for his project Thor at:
>> http://personal.inet.fi/atk/dncmrc/thor.htm
>> High frequency switchers have the advantage of being light weight although
>> they are more challenging to develop.
>> You could use the same series resonant circuit with the pig at a much
> lower
>> frequency. I would recommend a "soft switching" or resonantly commuted
>> design over a "hard switched" design.
>> There are so many possibilities that it comes down to the question of
> "what
>> are your objectives?" Simplicity? Weight? Power? Efficiency? Aesthetics?
>> Robustness?
>> 
>> 
>> Eddie Burwell
>> 
>>> 
>>> Cheers,
>>> 
>>> Greg Peters
>>> Department of Earth Sciences,
>>> University of Queensland, Australia
>>> Phone: 0402 841 677
>>> http://www.geocities-dot-com/gregjpeters
>>> 
>>> 
>>> 
>>> 
>>> 
>>> 
>> 
>> 
>> 
>> 
> 
> 
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