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[Amps] 3 phase power supply?

To: amps@contesting.com
Subject: [Amps] 3 phase power supply?
From: Steve Bookout <steve@nr4m.com>
Date: Sun, 2 Apr 2017 21:31:12 -0400
List-post: <amps@contesting.com">mailto:amps@contesting.com>
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


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