On 27 Dec 2004 22:15:16 -0800, wrote:

The problem we have run into is that we now have two Cold War era
civil defense sirens, but we don't have the money required to install
them. The representative from the Arizona Government estimated the
actual installation to be somewhere around $75,000. Our estimates upon
further investigation show it to be a smaller figure, but nevertheless
still a massively large amount. The two parts we stand in need of right
now are two 220 volt 50hp phase converters to go from 1 phase to 3
phase. These would be tax deductible, and we can provide proof of their
purpose for this project upon request. We are looking for a spare 50hp
phase converter that can be donated to our project. It does not need to
be new, used or surplus is absolutely fine. The exact specifications of
the civil defense siren are below:

We are starting off with a 220 volt, 200 amp, 1 phase line.
The siren we seek to power has three separate motors.
Motor 1 is a 7hp
Motor 2 is a 4.5hp
Motor 3 is a 1.5hp
RLA is 89amps, 220 volt, 3 phase

I was told by a specialist per these specifications that we needed
a 50hp phase converter. If anyone has a spare they can donate or knows
of a possibility for a donation, or can point us in the right
direction, or has any other helpful information for the project we
would deeply appreciate every little thing we can get at this point!
Thank you for your time in reading this letter. I deeply appreciate it.
In case my email address is blocked as I have begun to notice that many
usenet services do, I will spell it out here. It is: jkeagle13 at aol
dot com

Thank you!

I would question the assertion that you need a 50hp converter for this
application, especially if you can add a couple of time delay relays
to the controller so that the motors start one at a time. The
required size of the rotary converter can also be reduced by adding
phase correction capacitors to the larger load motors. The actual
size of the converter required depends partly on how much safety
factor the siren designers built in; if the actual mechanical load is
over 80% of the motor rating including the service factor, then a
seemingly oversized converter may really be required. Your local
specialist may have some information on this.

You can get a lot of good information about rotary phase converters
from the rec.crafts.metalworking newsgroup - a lot of the regulars
there use them for their machine tools and some of them have plans
posted in an archive somewhere which they will no doubt refer you to
if you inquire there, or you could find them with a search for "rotary
phase converter" in the newsgroup archives on google groups. I use
the design posted by Fitch (IIRC) and it works well even though I only
use a 5hp converter for a 5hp lathe motor (from which I only require
about 3hp output power, your application is different).

Nice project, good luck with it.

Glen