Re: diode selection + 3 phase supply

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

Original poster: "Sean Taylor by way of Terry Fritz <twftesla-at-qwest-dot-net>" <taylorss-at-rose-hulman.edu>

First, what is the rating of the pig?  the 3 phase power is equal to
sqrt(3)*VL*IL, that's line-to-line voltage and line current.  If you are
planning on powering it with 3 phase power, then I would use it Y connected
on the secondary (HV), and whatever it needs to be on the primary (LV).  If
you're using 208 V 3 phase (thats the line to line voltage, don't know what
it is in Au standard), and each of the transformer's LV windings are rated
for 120, it will have to be hooked up as a Y load.  The HV side can be
hooked up however you like - If you hook it up Y, then the line-to-line
voltage will be sqrt(3)*Vp, where Vp is the voltage of the secondary of just
one of the secondary windings.  IMHO, it would be best to hook it up Y, with
the center point grounded, and then to a charging inductor to a diode
(stack) from each transformer lead to your storage cap.  This will charge
your cap to a maximum of sqrt(2)*Vp, and it will recieve a peak 180 times
each second, as each of the phases peaks at 120 degrees apart.

My guess for the primary is it is made for a Y connection, which is the
standard for land use in the US, probably also in Au.  I don't know if your
transformer has schematics for Y and delta configurations, but BE CAREFUL
(of course), becuase if it is hooked up incorrectly, youre gonna either hurt
yourself, or not as big of a deal, blow a breaker, which might be bad in a
high power 3 phase system (some circuits have interrupt ratings of 20000 A,
or higher).

For the diodes, just use the first formula I wrote to calculate the line
current, and choose the diodes to handle at least 1.5 to 2 times that much
(maybe higher? I don't run a pig system, someone else interject here), maybe
more depending on how well you ballast it.  Pigs can put out much more than
they're rated for, granted you have the input power.  The diodes that you
should use for this don't need to be exceptionally fast - it's only 60 Hz.
Standard speed should work just fine.  The speed refers to how fast the
diode will stop conducting while it's forward biased, and then block current
in the reverse direction, and vice versa, ie how fast it will start
conducting when it is forward biased (usually much faster then the time to
stop conducting).

Hope all that helps, or wasn't too much information.  I would love to see
your power supply when done, along with the completed coil! must be a pretty
big one for that kind of power.

----------------------
Sean Taylor
The Geek Group
G-2 #1204
Because the geek shall inherit the Earth! (c)
www.thegeekgroup-dot-org



----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Tuesday, April 02, 2002 2:07 PM
Subject: diode selection + 3 phase supply


> Original poster: "Mr Gregory Peters by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <s371034-at-student.uq.edu.au>
>
> Hi all,
>
> I would like to make a DC coil by rectifying a 3 phase pole pig.
> Firstly, any hints? What effect do the star and delta configurations
> have when setting this up? Which is better? I'm wondering which diodes
> to use. There appears to be heaps of types such as standard, fast, ultra
> fast, etc. What does this mean?
>
> Cheers,
>
> Greg Peters
> Department of Earth Sciences,
> University of Queensland, Australia
> Phone: 0402 841 677
> http://www.geocities-dot-com/gregjpeters
>