[rescue] phase converters, was Re: Rescued: SGI Altix 450

[Cláudio Duarte]

Pensando aqui,  nC#o estava afim de falar esse assunto via voip aqui do
trabalho...
Por isso nC#o liguei ainda...

Pessoal passou lC! em casa ontem, me levaram para conhecer as pessoas, nego
ta Amarok Zero...
Cara, pessoal da alta que quer o serviC'o, de uma advocacia..

Alguma chance de um encontro pessoalmente hoje?

Estou na esplanada atC) 18, posso ficar um pouco mais.

As 19 eles querem saber se jC! falei contigo e se vocC* e sua "equipe" tem
interesse no projeto.

em fim...


Abs.

2016-07-29 13:08 GMT-03:00 Bob Darlington <rdarlington at gmail.com>:

> On Thu, Jul 28, 2016 at 6:43 PM, Dave McGuire <mcguire at neurotica.com>
> wrote:
>
> > On 07/28/2016 07:01 PM, Bob Darlington wrote:
> > > These work great for running the spindle motors in my shop.  I don't
> see
> > > any reason why they would't also work to power 3ph computers.  If
> you're
> > > running them on single phase power you have to derate them (also for
> > > altitude), typically a 5HP unit to run a 1 or 2 HP motor.  I buy mine
> > from
> > > AutomationDirect.com, GS2 units if I remember right.  You can select
> the
> > > output voltage, typically 208 volt, 3 phase for my stuff with 240 volt
> > > single phase residential power in.
> > >
> > > They work by taking in AC power, rectifying it, then inverting it back
> to
> > > AC at a frequency of your choice.  This is a pretty clean way to go.
> > >
> > > Do NOT use rotary phase converters unless by chance they had a major
> > design
> > > change over the years and spit out clean power.  Great for motors but
> > they
> > > cause early death of the computer running the milling machines.
> >
> >   Do you have any idea of the failure mode here?  It was my
> > understanding that rotary phase converters should work fine for this
> > sort of stuff, while (not to sound contradictory) the solid-state phase
> > converters mentioned above would not work for non-inductive, non-motor
> > loads.
> >
>
>
> Shooting from the hip here.  The rotary phase converters I played with put
> out what looked damn near like a square wave.   Sure, you'll have a 60 Hz
> component in there, but also every other odd harmonic at decreasing levels
> out to infinity.  I haven't tried my hand at building a 60Hz LPF with a
> 180Hz notch filter for that much power!   10MHz at maybe a watt, but not 60
> Hz.  Ordinary laptop power supplies start to sing in conditions like this.
> Audibly making high freqency noise from what is assumed (on my part) to be
> SMPS components (inductors in particular) operating at something other than
> the design frequency.  Aside from acoustic noise, you will also get
> heating.
>
> -Bob
>
>
>
> >
> >   The issue here is that with a whole lot of big transistors operating
> > in their active region, which would be needed for a 60Hz sine wave (or
> > three of them), which means a much bigger heat sink than those little
> > DIN-rail-mounted boxes could contain.  So they use a few banks of
> > smaller transistors restricted to either cutoff or saturation, not
> > active region but just switching, and create a stepped rough
> > approximation of a sine wave.  This will tear a switching power supply
> > apart, but with a big fat motor they're fine because the winding
> > inductance of the motor smooths out those stepped waveforms.
> >
> >                -Dave
> >
> > --
> > Dave McGuire, AK4HZ
> > New Kensington, PA
> > _______________________________________________
> > rescue list - http://www.sunhelp.org/mailman/listinfo/rescue
> _______________________________________________
> rescue list - http://www.sunhelp.org/mailman/listinfo/rescue
>



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ClC!udio Duarte
(61) 9934-3462