Re: [Emc-users] Phase converter project

[Gene Heskett]

On Monday 16 July 2018 13:46:13 andy pugh wrote:

> On 16 July 2018 at 16:17, Gene Heskett  wrote:
> > That derate would exceed 50% I'd imagine. And would nominally halve
> > the life of the caps. Not to mention the diode peak currents are now
> > much higher.  Sounds like a questionable lifetime result.  Would it
> > not be cheaper over the decades to buy the correct stuff, or even
> > pay for a three phase service upgrade?
>
> When we looked in to getting 3-phase for my dad's workshop the price
> was more than £20,000. ($US 26k, $CA35k, $AU36k, 10k Bahranian Dinar,
> to choose one which is "bigger")

Yikes! I wonder how far they had to go to get the 3rd phase? It may not 
have been that far, and I wasn't counting right of way deals either. 
Probably under a kilometer at that quote. But it does point out 
construction costs per city block as being stratospheric if the poles 
are not already populated. Some power companies here do it as a matter 
of being better able to balance loads, but thats a hard sell in the 
board room I expect.


-- 
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)
Genes Web page 

--
Check out the vibrant tech community on one of the world's most
engaging tech sites, Slashdot.org! http://sdm.link/slashdot
___
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users

Re: [Emc-users] Phase converter project

[andy pugh]

On 16 July 2018 at 16:17, Gene Heskett  wrote:

> That derate would exceed 50% I'd imagine. And would nominally halve the
> life of the caps. Not to mention the diode peak currents are now much
> higher.  Sounds like a questionable lifetime result.  Would it not be
> cheaper over the decades to buy the correct stuff, or even pay for a
> three phase service upgrade?

When we looked in to getting 3-phase for my dad's workshop the price
was more than £20,000. ($US 26k, $CA35k, $AU36k, 10k Bahranian Dinar,
to choose one which is "bigger")

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

--
Check out the vibrant tech community on one of the world's most
engaging tech sites, Slashdot.org! http://sdm.link/slashdot
___
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users

Re: [Emc-users] Phase converter project

[Gene Heskett]

On Monday 16 July 2018 10:22:28 andy pugh wrote:

> On 16 July 2018 at 14:37, Gene Heskett  wrote:
> >> While on the subject of voltage-increasing, apparently it is
> >> possible to re-wire the input stage of a 440V VFD into a doubler
> >> circuit to allow it to run (derated) off of 240V.
> >> https://en.wikipedia.org/wiki/Voltage_doubler#Delon_circuit
> >
> > Due to the physical size of the capacitors involved, I'd think it
> > impossible to shoehorn it into the 440 volt VFD.
>
> The idea is to re-arrange the existing input diodes and capacitors
> into a doubler arrangement.
>
> But you need to derate because caps sized for 3-phase full-wave are
> now seeing single-phase half-wave rectification.

That derate would exceed 50% I'd imagine. And would nominally halve the 
life of the caps. Not to mention the diode peak currents are now much 
higher.  Sounds like a questionable lifetime result.  Would it not be 
cheaper over the decades to buy the correct stuff, or even pay for a 
three phase service upgrade? If all 3 phases are on your street, not the 
case for me by at least a mile of new wire, but if it is, conversion 
costs shouldn't exceed a 4 digit cost.

Probably a good thing I am only in this as a hobby. So I pay for this 
stuff piecemeal, as needed to get some capability I don't have now.  
The "would be nice" category, but it doesn't pay the bills. ;-)

-- 
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)
Genes Web page 

--
Check out the vibrant tech community on one of the world's most
engaging tech sites, Slashdot.org! http://sdm.link/slashdot
___
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users

Re: [Emc-users] Phase converter project

[andy pugh]

On 16 July 2018 at 14:37, Gene Heskett  wrote:

>> While on the subject of voltage-increasing, apparently it is possible
>> to re-wire the input stage of a 440V VFD into a doubler circuit to
>> allow it to run (derated) off of 240V.
>> https://en.wikipedia.org/wiki/Voltage_doubler#Delon_circuit
>
> Due to the physical size of the capacitors involved, I'd think it
> impossible to shoehorn it into the 440 volt VFD.

The idea is to re-arrange the existing input diodes and capacitors
into a doubler arrangement.

But you need to derate because caps sized for 3-phase full-wave are
now seeing single-phase half-wave rectification.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

--
Check out the vibrant tech community on one of the world's most
engaging tech sites, Slashdot.org! http://sdm.link/slashdot
___
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users

Re: [Emc-users] Phase converter project

[Gene Heskett]

On Monday 16 July 2018 05:53:53 andy pugh wrote:

> On 16 July 2018 at 02:21, Dan Bloomquist  wrote:
> > 
>
> Interesting.
>
> Many years ago (before I knew much about electronics, before the
> Arduino was invented and before I taught myself C in order to write
> 3-phase drivers for LinuxCNC) I made a voltage-doubling rotary
> converter that very nearly worked...
>
> The idea was to connect 240V single phase to one leg and the
> star-point of a three-phase motor and to then take 440V three-phase
> out of the ends of each leg. I found that I needed to spin the motor
> up with a single-phase motor initially, but that it would then
> continue spinning on its  own. This was with no active control at all.
> It didn't produce particularly symmetrical 3-phase and would tend to
> bog down when a load motor came on line, so wasn't really a success,
> but did seem to have some promise.
>
> I wonder if this setup, with active control, could be made to work?

I think it could, useing 40 amp SSR's for the switching needed. Timeing 
of the drive signals would be required of course as the switching both 
ways would need to be done at the zero crossing point when turning the 
individual SSR on, else large, likely destructive current spikes would 
otherwise flow as a cap was brought into the circuit. Its an idea that  
needs checked out.
>
> While on the subject of voltage-increasing, apparently it is possible
> to re-wire the input stage of a 440V VFD into a doubler circuit to
> allow it to run (derated) off of 240V.
> https://en.wikipedia.org/wiki/Voltage_doubler#Delon_circuit

Due to the physical size of the capacitors involved, I'd think it 
impossible to shoehorn it into the 440 volt VFD.  It would take a 
separate box, but if it was big enough, the derate would not be 
noticeable. 

However, rather than huge high voltage electrolytic's, I think I'd prowl 
ebay looking for a big enough transformer, and just give the VFD the 
voltage it wants. Freight on a can big enough to run a 10 horse would 
apply, and someplace to put it that is code acceptable would also run 
the cost up. But it would be a one time cost.

And we shouldn't forget that these VFD's come with a recommendation to 
replace its big caps at (usually) 5 year intervals. Probably more 
important if feeding them single phase like I am as that increases the 
ripple currents flowing considerably. Over specing it by using a smaller 
motor will extend that somewhat as that also reduces the ripple 
currents. In my case a 1 hp motor and a 1.5 rated VFD.

I should probably note that the capacitative + diodes voltage doublers 
are outputing DC, and that the VFD's are cap voltage rated for at least 
1.41x the name plate source voltage, (which is above the 525 volt surge 
rating of the best electrolytic's) so if feeding them from such a DC 
source, you should figure on a tripler circuit as you'll need nominally 
620 volts in that case, but thats above the voltage withstand of the 
electrolytic chemistry since its dependant on the thickness of the alox 
film on the foil, and leakage currents rise rapidly above 525 volts for 
the best ones. Thats a big pile of caps that will need to be fan cooled. 
And replaced from time to time.  So while its possible, I'd stick with 
the big can solution. Much cheaper in the long view. The only "rent" you 
pay on the vfd's then is the cap replacements at the recommended 
interval.

-- 
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)
Genes Web page 

--
Check out the vibrant tech community on one of the world's most
engaging tech sites, Slashdot.org! http://sdm.link/slashdot
___
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users

Re: [Emc-users] Phase converter project

[andy pugh]

On 16 July 2018 at 02:21, Dan Bloomquist  wrote:

> 

Interesting.

Many years ago (before I knew much about electronics, before the
Arduino was invented and before I taught myself C in order to write
3-phase drivers for LinuxCNC) I made a voltage-doubling rotary
converter that very nearly worked...

The idea was to connect 240V single phase to one leg and the
star-point of a three-phase motor and to then take 440V three-phase
out of the ends of each leg. I found that I needed to spin the motor
up with a single-phase motor initially, but that it would then
continue spinning on its  own. This was with no active control at all.
It didn't produce particularly symmetrical 3-phase and would tend to
bog down when a load motor came on line, so wasn't really a success,
but did seem to have some promise.

I wonder if this setup, with active control, could be made to work?

While on the subject of voltage-increasing, apparently it is possible
to re-wire the input stage of a 440V VFD into a doubler circuit to
allow it to run (derated) off of 240V.
https://en.wikipedia.org/wiki/Voltage_doubler#Delon_circuit

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916

--
Check out the vibrant tech community on one of the world's most
engaging tech sites, Slashdot.org! http://sdm.link/slashdot
___
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users

[Emc-users] Phase converter project

[Dan Bloomquist]

I've pretty much completed my Phase Converter project. So far, I really 
like the way it works.




Any and all comments are welcome!

Thanks, Dan.


--
Check out the vibrant tech community on one of the world's most
engaging tech sites, Slashdot.org! http://sdm.link/slashdot
___
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users