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Re: 3 phase power converters

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On Saturday 03 August 2019 23:30:47 John Hasler wrote:

> A static converter doesn't produce three phase.  It converts a
> three-phase motor into a capacitor start, capacitor run single phase
> motor by connecting two of the phases to the single phase lines and
> connecting the third phase to one of the lines through capacitors.  It
> only works for motors and needs to be tuned for a specific motor.
>
> A real motor generator set *will* produce 60 Hz three phase because
> the motor and generator will be synchronous.  The power will also be
> seperately derived (not connected in any way to the single phase).
>
> More comon than real motor-generator sets are "rotary converters".
> These are large three phase motors wired up like the static converter
> discussed above but with slightly different capacitor values and not
> connected to any mechanical load.  Three phase loads are then
> connected to the phases of the motor.  This produces a fair
> approximation of three phase but note that two of the phases are
> connected to the single phase lines.  This means that you have neither
> a neutral nor a grounded conductor (unless you are in Europe in which
> case you have
> corner-grounded delta).

Three phase, at most any frequency can be had a lot cheaper at up to 10 
horse or so by using a suitably sized VFD. I'm useing 2 1.5 horse rated, 
to drive a 1 horse 3 phase motor, currently available from ebay for 
about a hundred bucks. Top frequency is 400 hz, but motor inductance 
reduces the drive currant to under an amp a phase at around 200 hz, so 
theres little torque to do work above 150 hz.  But I can get turn the 
house around torque at 5 hz, not forever because the  motors fan does 
not move cooling air when its not running at normal speed. But for a 20 
minute job its fine. Lathe itself has an 8 speed drive, rarely changed 
out of 5th, the vfd does it all.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/gene>

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3 phase power converters (was: Re: 3 phase power (was Re: Wireless home LAN - WiFi vs Bluetooth?)) rhkramer@gmail.com - 2019-08-04 03:40 +0200
  Re: 3 phase power converters John Hasler <jhasler@newsguy.com> - 2019-08-04 05:40 +0200
    Re: 3 phase power converters Gene Heskett <gheskett@shentel.net> - 2019-08-04 06:20 +0200
      Re: 3 phase power converters John Hasler <jhasler@newsguy.com> - 2019-08-04 16:50 +0200
        Re: 3 phase power converters Gene Heskett <gheskett@shentel.net> - 2019-08-04 18:00 +0200

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