[Amps] 3 phase power supply?

[Steve Bookout]

Hello all,

Figured I would ask the amps 'brain trust' about this.

I recently was given a URT23 military amp, power supply and exciter.  It 
looks 'as new' and has all the interconnect cables.

The final amp is a pair of 4cx1500b's and is rated for a KW any mode.

Here is the problem.  The power supply is a 3 phase supply for 208 volts 
or 440 volts, (as I recall.)  Trying to figure out my best option for 
powering this up.

(Note:  I don't usually thing 'out of the box', which is why I'm asking 
here.)

http://www.practicalmachinist.com/FitchWConverter.pdf

http://www.practicalmachinist.com/vb/redirect-to/?redirect=http%3A%2F%2Fwww.metalwebnews.com%2Fhowto%2Fph-conv%2Fph-conv.html

http://www.practicalmachinist.com/vb/redirect-to/?redirect=http%3A%2F%2Fwww.homemetalshopclub.org%2Fprojects%2Fphconv%2Fphconv.html

I currently have a 5 hp rotary phase converter which I use with a 
milling machine.   What I have found on building a rotary phase 
converter indicates that 'normally' you would wind up with ~10% more 
voltage than the single phase you started with.  I surely don't need 
260+ volts, when I'm looking for 208 volts.  I suppose I could use a 240 
volt variac to reduce the voltage on the 3 phase output.

But, another thing to consider.  I was looking a the schematic and saw 
where some of the smaller transformers were fed from one phase, while 
the HV was fed by two phases.  Again, from what I read, the voltages of 
the 3 phases created from a rotary converter, vary according to the 
load.  My concern is with the filament supply.  If it's off one leg, and 
I was to vary the 240 input to get exactly what I need for the filament, 
what happens when I start drawing power and that leg now changes by 10 
%, or so.

Other choice is to just build a new 240 volt single phase supply for all 
the required voltages.  It's just that the 3 phase supply is part of a 
really clean 'system' and it would be nice to keep it original, if 
possible.  This seems like it would be the most stable and reliable.

Thoughts?

73 de Steve, NR4M